Drought Stress Effects on Growth, ROS Markers, Compatible Solutes, Phenolics, Flavonoids, and Antioxidant Activity in Amaranthus tricolor

Effect of kaolin on productivity, anatomical and biochemical responses to water deficit in Pelargonium graveolens grown in sandy soil

The objective of this study was to examine the response of geranium plants to different irrigation levels (100%, 80%, and 60% based on ETo) and Kaolin application rates (0, 100, 200 and 300 ppm) during 2022 and 2023 seasons, at Aly Mobarak Experimental Farm, Horticulture Research Station, located at El-Bustan site, El-Behiera Governorate, Egypt, by using a two-way factorial analysis experimental design. The results revealed that water deficit significantly reduced most studied traits. Irrigation level at 60% based on ETo exhibited poorest performance on growth parameters and decreased fresh yield and essential oil yield by 27.77% 10.73%, respectively as compared with full irrigated plants. However, foliar application of kaolin at 200 and 300 ppm led to increasing biomass accumulation by 28.51, 26.16%, and essential oil yield by 79.51, 89.95%, respectively, as compared with untreated plants grown under the same level of water deficit (60% based on ETo). GC-MS analysis of essential oil showed that water deficit and kaolin application increased geraniol/citronellol ratio and consequently improved oil quality. Results highlight the positive influence of water deficit and kaolin rates on the development and performance of anatomical parameters. Enzymes assay in leaves revealed in an increase superoxide dismutase (SOD) and peroxidase (POD) activities, and decreased in catalase (CAT) activity under water deficit. As for WUE at 60%, followed by 80% based on ETo recorded excellent response for geranium plants which led to more water saving. So, it could be concluded that foliar application of kaolin at 200 and 300 ppm obtained the optimal characteristics of geranium plants under experimental conditions. In particular, essential oil yield and productivity.

Ecophysiological, transcriptomic and metabolomic analyses shed light on the response mechanism of Bruguiera gymnorhiza to upwelling stress

Mangroves, due to their unique habitats, endure dual stressors from land to ocean and ocean to land directions. While extensive researches have been conducted on land-ocean stressors, studies on ocean-land stressors like upwelling are considerably scarce. In this study, ecophysiological, transcriptome, and metabolome analyses were conducted to determine the responses of mangrove plant (Bruguiera gymnorhiza, B. gymnorhiza) to upwelling stress. The results suggested that upwelling stress in B. gymnorhiza induces oxidative stress and membrane damage, which are mitigated by the synergistic actions of antioxidant enzymes and osmoprotectants. Transcriptomic and metabolomic analyses revealed that upregulated genes related to oxidation-reduction and carbohydrate metabolism, along with accumulated metabolites such as amino acids, lipids, phenols, and organic acids, contribute to enhancing antioxidant capacity and maintaining osmotic balance. Further analysis identified key KEGG pathways involved in the response to upwelling stress, including amino acid metabolism, carbohydrate and energy metabolism, flavonoid biosynthesis, and plant hormone signal transduction. These findings provide vital information into the multi-level response mechanisms of mangrove plants to upwelling stress.

Evaluation of growth, physiological response, and drought resistance of different flue-cured tobacco varieties under drought stress

Background

In recent years, more severe droughts have occurred frequently in many parts of the world, drought stress is the primary abiotic stress factor restricting the growth and quality of flue-cured tobacco. Therefore, screening dryland cultivation-compatible flue-cured tobacco varieties will help reduce the negative impact of drought.

Methods

Tobacco varieties were selected: Qinyan 96 (Q96), Zhongyan 101 (Z101), Yunyan 87 (Y87), and Yunyan 116 (Y116). A pot experiment was conducted with four water supply gradients: sufficient, mild stress, moderate stress, and severe stress. The aim was to analyze inter-varietal differences in agronomic traits, photosynthetic traits, reactive oxygen species (ROS) metabolism, and antioxidant enzyme system under drought stress. Additionally, the drought resistance of four flue-cured tobacco varieties was evaluated using principal component analysis and membership function analysis.

Results

The results showed that drought intensification inhibited seedling growth and development across all varieties, with Q96 showing the least decrease and Y116 the greatest. With the increasing degree of drought stress, photosynthetic rates (Pn), transpiration rate (Tr), and stomatal conduction (Gs) have shown gradually decreasing trends, while substomatal cavity CO2 concentration (Ci) showed a growing trend. Severe drought corresponded with lower chlorophyll content and decreased the maximal photochemical efficiency (Fv/Fm), photosystem II (PSII), and photochemical quenching coefficient (qP) in all varieties, while steady-state non-photochemical quenching (NPQ) increased. Increased drought stress led to significantly higher reactive oxygen species (ROS) and malondialdehyde (MDA) content accumulation in tobacco seedlings. The antioxidant enzyme activities in, Q96, Z101, and Y87 increased under mild drought stress, whereas Y116 showed decreased activity.

Conclusion

The drought resistance ranking among the four varieties is as follows: Q96 > Z101 > Y87 > Y116. Therefore, Q96 is a promising drought-tolerant breeding material that can be used as a reference for dryland cultivation of flue-cured tobacco.

Manure-biochar compost mitigates the soil salinity stress in tomato plants by modulating the osmoregulatory mechanism, photosynthetic pigments, and ionic homeostasis

One of the main abiotic stresses that affect plant development and lower agricultural productivity globally is salt in the soil. Organic amendments, such as compost and biochar can mitigate the opposing effects of soil salinity (SS) stress. The purpose of this experiment was to look at how tomato growth and yield on salty soil were affected by mineral fertilization and manure-biochar compost (MBC). Furthermore, the study looked at how biochar (organic amendments) work to help tomato plants that are stressed by salt and also a mechanism by which biochar addresses the salt stress on tomato plants. Tomato yield and vegetative growth were negatively impacted by untreated saline soil, indicating that tomatoes are salt-sensitive. MBC with mineral fertilization increased vegetative growth, biomass yield, fruit yield, chlorophyll, and nutrient contents, Na/K ratio of salt-stressed tomato plants signifies the ameliorating effects on tomato plant growth and yield, under salt stress. Furthermore, the application of MBC with mineral fertilizer decreased H2O2, but increased leaf relative water content (RWC), leaf proline, total soluble sugar, and ascorbic acid content and improved leaf membrane damage, in comparison with untreated plants, in response to salt stress. Among the composting substances, T7 [poultry manure-biochar composting (PBC) (1:2) @ 3 t/ha + soil-based test fertilizer (SBTF)] dose exhibited better-improving effects on salt stress and had maintained an order of T7 > T9 > T8 > T6 in total biomass and fruit yield of tomato. These results suggested that MBC might mitigate the antagonistic effects of salt stress on plant growth and yield of tomatoes by improving osmotic adjustment, antioxidant capacity, nutrient accumulation, protecting photosynthetic pigments, and reducing ROS production and leaf damage in tomato plant leaves.

Enhancing drought tolerance in Malva parviflora plants through metabolic and genetic modulation using Beauveria bassiana inoculation

BACKGROUND

Enhancing crops' drought resilience is necessary to maintain productivity levels. Plants interact synergistically with microorganisms like Beauveria bassiana to improve drought tolerance. Therefore, the current study investigates the effects of biopriming with B. bassiana on drought tolerance in Malva parviflora plants grown under regular irrigation (90% water holding capacity (WHC)), mild (60% WHC), and severe drought stress (30% WHC).

RESULTS

The results showed that drought stress reduced the growth and physiological attributes of M. parviflora. However, those bioprimed with B. bassiana showed higher drought tolerance and enhanced growth, physiological, and biochemical parameters: drought stress enriched malondialdehyde and H2O2 contents. Conversely, exposure to B. bassiana reduced stress markers and significantly increased proline and ascorbic acid content under severe drought stress; it enhanced gibberellic acid and reduced ethylene. Bioprimed M. parviflora, under drought conditions, improved antioxidant enzymatic activity and the plant's nutritional status. Besides, ten Inter-Simple Sequence Repeat primers detected a 25% genetic variation between treatments. Genomic DNA template stability (GTS) decreased slightly and was more noticeable in response to drought stress; however, for drought-stressed plants, biopriming with B. bassiana retained the GTS.

CONCLUSION

Under drought conditions, biopriming with B. bassiana enhanced Malva's growth and nutritional value. This could attenuate photosynthetic alterations, up-regulate secondary metabolites, activate the antioxidant system, and maintain genome integrity.

Comprehensive evaluation of drought tolerance of six Chinese chestnut varieties (clones) based on flavonoids and other physiological indexes

Flavonoids are crucial secondary metabolites that possess the ability to mitigate UV damage and withstand both biotic and abiotic stresses. Therefore, it is of immense significance to investigate the flavonoid content as a pivotal indicator for a comprehensive assessment of chestnut's drought tolerance. This study aimed to determine the flavonoid content and drought tolerance-related physiological and biochemical indices of six chestnut varieties (clones) grafted trees-Qianxi 42 (QX42), Qinglong 45 (QL45), Yanshanzaofeng (YSZF), Yanzi (YZ), Yanqiu (YQ), and Yanlong (YL)-under natural drought stress. The results were used to comprehensively analyze the drought tolerance ability of these varieties. The study revealed that the ranking of drought tolerance indices in terms of their ability to reflect drought tolerance was as follows: superoxide (oxide) dismutase (SOD) activity, ascorbate peroxidase (APX) activity, flavone content, catalase (CAT) activity, proline (PRO) content, soluble sugar content, peroxidase (POD) activity, betaine content, flavonol content, hydrogen peroxide (H2O2) content, soluble protein content, superoxide ion (OFR) content, superoxide (ion OFR) production rate, malondialdehyde (MDA) content, chlorophyll content. Through principal component analysis, the contents of flavonoids and flavonols can be used as indicators for comprehensive evaluation of drought tolerance of chestnut. The comprehensive evaluation order of drought tolerance of grafted trees of 6 chestnut varieties (Clones) was: QL45 > QX42 > YQ > YZ > YSZF > YL.

Genome-Wide Identification of the Cation/Proton Antiporter (CPA) Gene Family and Functional Analysis of AtrNHX8 under Salt Stress

Amaranthus tricolor is an important vegetable, and its quality is affected by salt stress. Cation/proton antiporters (CPA) contribute to plant development and tolerance to salt stress. In this study, 35 CPA genes were identified from a genome database for A. tricolor, including 9 NHX, 5 KEA, and 21 CPA2 genes. Furthermore, in A. tricolor, the expression levels of most AtrNHX genes were higher at a low salinity level (50 or 100 mM NaCl) than in the control or 200 mM NaCl treatment. Levels of most AtrNHX genes were elevated in the stem. Moreover, AtrNHX8 was homologous to AtNHX4, which is involved in the regulation of sodium homeostasis and salt stress response. After AtrNHX8 overexpression in Arabidopsis thaliana, seed germination was better, and the flowering time was earlier than that of wild-type plants. Additionally, the overexpression of AtrNHX8 in A. thaliana improved salt tolerance. These results reveal the roles of AtrNHX genes under salt stress and provide valuable information on this gene family in amaranth.

Iron nanoparticles in combination with other conventional Fe sources remediate mercury toxicity-affected plants and soils by nutrient accumulation in bamboo species

The issue of mercury (Hg) toxicity has recently been identified as a significant environmental concern, with the potential to impede plant growth in forested and agricultural areas. Conversely, recent reports have indicated that Fe, may play a role in alleviating HM toxicity in plants. Therefore, this study's objective is to examine the potential of iron nanoparticles (Fe NPs) and various sources of Fe, particularly iron sulfate (Fe SO4 or Fe S) and iron-ethylene diamine tetra acetic acid (Fe - EDTA or Fe C), either individually or in combination, to mitigate the toxic effects of Hg on Pleioblastus pygmaeus. Involved mechanisms in the reduction of Hg toxicity in one-year bamboo species by Fe NPs, and by various Fe sources were introduced by a controlled greenhouse experiment. While 80 mg/L Hg significantly reduced plant growth and biomass (shoot dry weight (36%), root dry weight (31%), and shoot length (31%) and plant tolerance (34%) in comparison with control treatments, 60 mg/L Fe NPs and conventional sources of Fe increased proline accumulation (32%), antioxidant metabolism (21%), polyamines (114%), photosynthetic pigments (59%), as well as root dry weight (25%), and shoot dry weight (22%), and shoot length (22%). Fe NPs, Fe S, and Fe C in plant systems substantially enhanced tolerance to Hg toxicity (23%). This improvement was attributed to increased leaf-relative water content (39%), enhanced nutrient availability (50%), improved antioxidant capacity (34%), and reduced Hg translocation (6%) and accumulation (31%) in plant organs. Applying Fe NPs alone or in conjunction with a mixture of Fe C and Fe S can most efficiently improve bamboo plants' tolerance to Hg toxicity. The highest efficiency in increasing biochemical and physiological indexes under Hg, was related to the treatments of Fe NPs as well as Fe NPs + FeS + FeC. Thus, Fe NPs and other Fe sources might be effective options to remove toxicity from plants and soil. The future perspective may help establish mechanisms to regulate environmental toxicity and human health progressions.

Nutritional and bioactive properties and antioxidant potential of Amaranthus tricolor, A. lividus, A viridis, and A. spinosus leafy vegetables

Climate change results in continuous warming of the planet, threatening sustainable crop production around the world. Amaranth is an abiotic stress-tolerant, climate-resilient, C4 leafy orphan vegetable that has grown rapidly with great divergence and potential usage. The C4 photosynthesis allows amaranth to be grown as a sustainable future food crop across the world. Most amaranth species grow as weeds in many parts of the world, however, a few amaranth species can be also found in cultivated form. Weed species can be used as a folk medicine to relieve pain or reduce fever thanks to their antipyretic and analgesic properties. In this study, nutritional value, bioactive pigments, bioactive compounds content, and radical scavenging potential (RSP) of four weedy and cultivated (WC) amaranth species were evaluated. The highest dry matter, carbohydrate content, ash, content of iron, copper, sodium, boron, molybdenum, zinc, β-carotene and carotenoids, vitamin C, total polyphenols (TP), RSP (DPPH), and RSP (ABTS+) was determined in Amaranthus viridis (AV). On the other hand, A. spinosus (AS) was found to have the highest content of protein, fat, dietary fiber, manganese, molybdenum, and total flavonoids (TF). In A. tricolor (AT) species the highest total chlorophyll, chlorophyll a and b, betaxanthin, betacyanin, and betalain content was determined. A. lividus (AL) was evaluated as the highest source of energy. AV and AT accessions are underutilized but promising vegetables due to their bioactive phytochemicals and antioxidants.

Genome-wide analyses of the GbAP2 subfamily reveal the function of GbTOE1a in salt and drought stress tolerance in Ginkgo biloba

The APETALA2 (AP2) transcription factors play crucial roles in plant growth and stage transition. Ginkgo biloba is an important medicinal plant renowned for the rich flavonoid content in its leaves. In this study, 18 GbAP2s were identified from the G. biloba genome and classified into three clusters. We found that the members of the euAP2 cluster, including four TOEs (GbTOE1a/1b/1c/3), exhibited a higher expression level in most samples compared to other members. Specifically, GbTOE1a may have a positive regulatory role in salt and drought stress responses. The overexpression of GbTOE1a in G. biloba calli resulted in a significant increase in the flavonoid content and upregulation of flavonoid biosynthesis genes, including PAL, 4CL, CHS, F3H, FLSs, F3'Hs, OMT, and DFRs. By contrast, the silencing of GbTOE1a in seedlings decreased the flavonoid content and the expression of flavonoid synthesizing genes. In addition, the silenced seedlings exhibited decreased antioxidant levels and a higher sensitivity to salt and drought treatments, suggesting a crucial role of GbTOE1a in G. biloba salt and drought tolerance. To the best of our knowledge, this was the first investigation into the identification and characterization of GbAP2s in G. biloba. Our results lay a foundation for further research on the regulatory role of the AP2 family in flavonoid synthesis and stress responses.

Effect of oil contaminants on antioxidant responses and antioxidant properties of Pleurotus florida (P. Kumm)

This research investigated the antioxidant responses of Pleurotus florida at different concentrations of gas oil [0% (control), 2.5%, 5%, and 10% (v:v)] for 30 days. The activities of superoxide dismutase and catalase enzymes decreased in responses to the gas oil presence by an average of 83% and 49%, respectively. In contrast, the activities of the ascorbate peroxidase and glutathione peroxidase enzymes displayed an upward trend in the groups cultured in oil-contaminated media. The gas oil contaminant increased total phenol and flavonoid accumulation, reflecting the variation in secondary metabolism. According to the 1,2-diphenyl-2-picrylhydrazyl radical scavenging, the 2.5% gas oil treatment resulted in the highest antioxidant activity (48 μg mL-1). The highest scavenging activity of nitric oxide radicals (IC50 = 272 μg mL-1) was observed in the treatment with the highest gas oil concentration (10%). Also, this treatment showed an excellent ability to chelate Fe+2 ions (IC50 = 205 μg mL-1). The IC50 values of methanolic extract for nitric oxide scavenging activity and metal chelating ability were significantly reduced by increasing gas oil concentration in the treatments. With increasing the gas oil concentration, malondialdehyde content as a criterion measure of lipid peroxidation level showed significant reduction. These results show that P. florida is resistant to and a compatible mushroom with oil pollutants. Also, the activity of glutathione peroxidase and the ascorbate-glutathione cycle detoxify nitric oxide radicals and products of reactive oxygen species-induced lipid peroxidation in the gas oil treatments.

Impact of bacterial volatiles on the plant growth attributes and defense mechanism of rice seedling

Rice is a major dietary element for about two billion people worldwide and it faces numerous biotic and abiotic stress for its cultivation. Rice blast disease caused by Magnaporthe oryzae reduce up to 30 % rice yield. Overuse of synthetic chemicals raises concerns about health and environment; so, there is an urgent need to explore innovative sustainable strategies for crop productivity. The main aim of this study is to explore the impact of bacterial volatiles (BVCs) on seedling growth and defense mechanisms of rice under in-vitro condition. On the basis of plant growth promoting properties, six bacterial strains were selected out of ninety-one isolated strains for this study; Pantoea dispersa BHUJPVR01, Enterobacter cloacae BHUJPVR02, Enterobacter sp. BHUJPVR12, Priestia aryabhattai BHUJPVR13, Pseudomonas sp. BHUJPVWRO5 and Staphylococcus sp. BHUJPVWLE7. Through the emission of bacterial volatiles compounds (BVCs), Enterobacter sp., P. dispersa and P. aryabhattai significantly reduces the growth of rice blast fungus Magnaporthe oryzae by 69.20 %, 66.15 % and 62.31 % respectively. Treatment of rice seedlings with BVCs exhibited significant enhancement in defence enzyme levels, including guaiacol peroxidase, polyphenol oxidase, total polyphenols, and total flavonoids by a maximum of up to 24 %, 48 %, 116 % and 80 %, respectively. Furthermore, BVCs effectively promote shoot height, root height, and root counts of rice. All BVCs treated plant showed a significant increase in shoot height. P. dispersa treated plants showed the highest increase of 60 % shoot and 110 % root length, respectively. Root counts increased up to 30% in plants treated with E. cloacae and Staphylococcus sp. The BVCs can be used as a sustainable approach for enhancing plant growth attributes, productivity and defence mechanism of rice plant under biotic and abiotic stresses.

Potassium augments growth, yield, nutrient content, and drought tolerance in mung bean (Vigna radiata L. Wilczek.)

Uneven rainfall and high temperature cause drought in tropical and subtropical regions which is a major challenge to cultivating summer mung bean. Potassium (K), a major essential nutrient of plants can alleviate water stress (WS) tolerance in plants. A field trial was executed under a rainout shelter with additional K fertilization including recommended K fertilizer (RKF) for relieving the harmful impact of drought in response to water use efficiency (WUE), growth, yield attributes, nutrient content, and yield of mung bean at the Regional Agricultural Research Station, BARI, Ishwardi, Pabna in two successive summer season of 2018 and 2019. Drought-tolerant genotype BMX-08010-2 (G1) and drought-susceptible cultivar BARI Mung-1 (G2) were grown by applying seven K fertilizer levels (KL) using a split-plot design with three replications, where mung bean genotypes were allotted in the main plots, and KL were assigned randomly in the sub-plots. A considerable variation was observed in the measured variables. Depending on the different applied KL and seed yield of mung bean, the water use efficiency (WUE) varied from 4.73 to 8.14 kg ha-1 mm-1. The treatment applying 125% more K with RKF (KL7) under WS gave the maximum WUE (8.14 kg ha-1 mm-1) obtaining a seed yield of 1093.60 kg ha-1. The treatment receiving only RKF under WS (KL2) provided the minimum WUE (4.73 kg ha-1 mm-1) attaining a seed yield of 825.17 kg ha-1. Results showed that various characteristics including nutrients (N, P, K, and S) content in stover and seed, total dry matter (TDM) in different growth stages, leaf area index (LAI), crop growth rate (CGR), root volume (RV), root density (RD), plant height, pod plant-1, pod length, seeds pod-1, seed weight, and seed yield in all pickings increased with increasing K levels, particularly noted with KL7. The highest grain yield (32.52%) was also obtained from KL7 compared to lower K with RKF. Overall, yield varied from 1410.37 kg ha-1 using 281 mm water (KL1; well-watered condition with RKF) to 825.17 kg ha-1 using 175 mm water (KL2). The results exhibited that the application of additional K improves the performance of all traits under WS conditions. Therefore, mung beans cultivating under WS requires additional K to diminish the negative effect of drought, and adequate use of K contributes to accomplishing sustainable productivity.

Significance of phosphorus deficiency for the mitigation of mercury toxicity in the Robinia pseudoacacia L.- rhizobia symbiotic association

Nitrogen (N2)-fixing legumes can be used for phytoremediation of toxic heavy metal Mercury (Hg) contaminated soil, but N2-fixation highly relies on phosphorus (P) availability for nodule formation and functioning. Here, we characterized the significance of P deficiency for Hg accumulation and toxicity in woody legume plants. Consequences for foliar and root traits of rhizobia inoculation, Hg exposure (+Hg) and low P (-P) supply, individually and in combination were characterized at both the metabolite and transcriptome levels in seedlings of two Robinia pseudoacacia L. provenances originating from contrasting climate and soil backgrounds, i.e., GS in northwest and the DB in northeast China. Our results reveal that depleted P mitigates the toxicity of Hg at the transcriptional level. In leaves of Robinia depleted P reduced oxidative stress and improved the utilization strategy of C, N and P nutrition; in roots depleted P regulated the expression of genes scavenging oxidative stress and promoting cell membrane synthesis. Rhizobia inoculation significantly improved the performance of both Robinia provenances under individual and combined +Hg and -P by promoting photosynthesis, increasing foliar N and P content and reducing H2O2 and MDA accumulation despite enhanced Hg uptake. DB plants developed more nodules, had higher biomass and accumulated higher Hg amounts than GS plants and thus are suggested as the high potential Robinia provenance for future phytoremediation of Hg contaminated soils with P deficiency.

Role of calcium signaling in cadmium stress mitigation by indol-3-acetic acid and gibberellin in chickpea seedlings

Given the adverse impacts of heavy metals on plant development and physiological processes, the present research investigated the protective role of indole-3-acetic acid (IAA) and gibberellic acid (GA3) against cadmium (Cd)-induced injury in chickpea seedlings. Therefore, seeds germinated for 6 days in a medium containing 200 μM Cd alone or combined with 10 μM GA3 or 10 μM IAA. Both GA3 and IAA mitigated Cd-imposed growth delays in roots and shoots (80% and 50% increase in root and shoot length, respectively). This beneficial effect was accompanied by a significant reduction in Cd2+ accumulation in both roots (74% for IAA and 38% for GA3) and shoots (68% and 35%, respectively). Furthermore, these phytohormones restored the cellular redox state by reducing the activity of NADPH oxidase and downregulating the transcription level of RbohF and RbohD genes. Likewise, hydrogen peroxide contents were reduced by GA3 and IAA supply. Additionally, GA3 and IAA countered the Cd-induced reduction in total phenols, flavonoids, and reducing sugars in both roots and shoots. The exogenous effectors enhanced the activities of catalase, ascorbate peroxidase, and thioredoxin, as well as the corresponding gene expressions. Interestingly, adding GA3 and IAA to the Cd-contaminated germination media corrected the level of calcium (Ca2+) ion within seedling tissues. This effect coincided with the upregulation of key genes associated with stress sensing and signal transduction, including auxin-binding protein (ABP19a), mitogen-activated protein kinase (MAPK2), calcium-dependent protein kinase (CDPK1), and calmodulin (CaM). Overall, the current results suggest that GA3 and IAA sustain the Ca2+ signaling pathway, resulting in metal phytotoxicity relief. Amendment of agricultural soils contaminated with heavy metals with GA3 or IAA could represent an effective practice to improve crop yield.

Waterlogging faced by bulbil expansion improved the growth of Pinellia ternata and its effect reinforced by brassinolide

The bulbil expansion of P. ternata is a key period for its yield formation, and the process of bulbil expansion is often subjected to short-term heavy precipitation. It is not clear whether the short-term waterlogging can affect bulbil expansion. Brassinolide (BR) is widely believed to enhance plant tolerance to abiotic stress. The study investigated the effects of normal water (C), waterlogging (W), waterlogging + BR (W + B), waterlogging + propiconazole (W + P) on P. ternata at the bulbil expansion period in order to assess P. ternata's ability to cope with waterlogging during the bulbil expansion stage and the regulation effects of BR on the process. The biomass of P. ternata was significantly increased after waterlogging. W treatment significantly reduced the H2O2 and MDA contents, the rate of O2⋅- production and the activities of antioxidant enzymes compared with the C group. AsA and GSH contents were significantly reduced by W treatment. However, the ratios of AsA/DHA and GSH/GSSG were slightly affected by W treatment. The rate of O2∙- production and H2O2 content in W + B group were significantly lower than those in W group. The POD, APX, and GR activities, and GSH content in W + B group were evidently increased compared with the W group. Soluble sugar and active ingredients contents were significantly increased after waterlogging, and the enhancement was reinforced by BR. In conclusion, waterlogging reduced oxidative stress in P. ternata under the experimental conditions. BR treatment under waterlogging had a positive effect on P. ternata by enhancing antioxidant capacity and promoting the accumulation of soluble sugars and active ingredients.

Antagonistic effect of mercury and excess nitrogen exposure reveals provenance-specific phytoremediation potential of black locust-rhizobia symbiosis

Interaction of different environmental constrains pose severe threats to plants that cannot be predicted from individual stress exposure. In this context, mercury (Hg), as a typical toxic and hazardous heavy metal, has recently attracted particular attention. Nitrogen (N2)-fixing legumes can be used for phytoremediation of Hg accumulation, whereas N availability could greatly affect its N2-fixation efficiency. However, information on the physiological responses to combined Hg exposure and excess N supply of woody legume species is still lacking. Here, we investigated the interactive effects of rhizobia inoculation, Hg exposure (+Hg), and high N (+N) supply, individually and in combination (+N*Hg), on photosynthesis and biochemical traits in Robinia pseudoacacia L. seedlings of two provenances, one from Northeast (DB) and one from Northwest (GS) China. Our results showed antagonistic effects of combined + N*Hg exposure compared to the individual treatments that were provenance-specific. Compared to individual Hg exposure, combined + N*Hg stress significantly increased foliar photosynthesis (+50.6%) of inoculated DB seedlings and resulted in more negative (-137.4%) δ15N abundance in the roots. Furthermore, combined + N*Hg stress showed 47.7% increase in amino acid N content, 39.4% increase in NR activity, and 14.8% decrease in MDA content in roots of inoculated GS seedlings. Inoculation with rhizobia significantly promoted Hg uptake in both provenances, reduced MDA contents of leaves and roots, enhanced photosynthesis and maintained the nutrient balance of Robinia. Among the two Robinia provenances investigated, DB seedlings formed more nodules, had higher biomass and Hg accumulation than GS seedlings. For example, total Hg concentrations in leaves and roots and total biomass of inoculated DB seedlings were 1.3,1.9 and 3.4 times higher than in inoculated GS seedlings under combined + N*Hg stress, respectively. Therefore, the DB provenance is considered to possess a higher potential for phytoremediation of Hg contamination compared to the GS provenance in environments subjected to N deposition.

Unraveling the transcriptional network regulated by miRNAs in blast-resistant and blast-susceptible rice genotypes during Magnaporthe oryzae interaction

The plant pathogen Magnaporthe oryzae poses a significant threat to global food security, and its management through the cultivation of resistant varieties and crop husbandry practices, including fungicidal sprays, has proven to be inadequate. To address this issue, we conducted small-RNA sequencing to identify the roles of miRNAs and their target genes in both resistant (PB1637) and susceptible (PB1) rice genotypes. We confirmed the expression of differentially expressed miRNAs using stem-loop qRT-PCR analysis and correlated them with rice patho-phenotypic and physio-biochemical responses. Our findings revealed several noteworthy differences between the resistant and susceptible genotypes. The resistant genotype exhibited reduced levels of total chlorophyll and carotenoids compared to the susceptible genotype. However, it showed increased levels of total protein, callose, H2O2, antioxidants, flavonoids, and total polyphenols. Additionally, among the defense-associated enzymes, guaiacol peroxidase and polyphenol oxidase responses were higher in the susceptible genotypes. In our comparative analysis, we identified 27 up-regulated and 43 down-regulated miRNAs in the resistant genotype, while the susceptible genotype exhibited 44 up-regulated and 62 down-regulated miRNAs. Furthermore, we discovered eight up-regulated and five down-regulated miRNAs shared between the resistant and susceptible genotypes. Notably, we also identified six novel miRNAs in the resistant genotype and eight novel miRNAs in the susceptible genotype. These novel miRNAs, namely Chr8_26996, Chr12_40110, and Chr12_41899, were found to negatively correlate with the expression of predicted target genes, including Cyt-P450 monooxygenase, serine carboxypeptidase, and zinc finger A20 domain-containing stress-associated protein, respectively. The results of our study on miRNA and transcriptional responses provide valuable insights for the development of future rice lines that are resistant to blast disease. By understanding the roles of specific miRNAs and their target genes in conferring resistance, we can enhance breeding strategies and improve crop management practices to ensure global food security.

Proteomics and phosphoproteomics reveal the different drought-responsive mechanisms of priming with (Z)-3-hexenyl acetate in two tea cultivars

Drought is an important abiotic stress that constrains the quality and quantity of tea plants. The green leaf volatiles Z-3-hexenyl acetate (Z-3-HAC) have been reported to play an essential role in stress responses. However, the underlying mechanisms of drought tolerance in tea plants remain elusive. This study investigated the physiological, proteomic, and phosphoproteomic profiling of two tea plant varieties of Longjingchangye (LJCY) and Zhongcha 108 (ZC108) with contrasting drought tolerance characteristics under drought stress. Physiological data showed that spraying Z-3-HAC exhibited higher activities of superoxide dismutase (SOD) and catalase (CAT) in both LJCY and ZC108 but lower content of malondialdehyde (MDA) in LJCY under drought stress. The proteomic and phosphoproteomic analysis suggested that the drought tolerance mechanism of Z-3-HAC in LJCY and ZC108 was different. Proteomic analyses revealed that Z-3-HAC enhanced the drought tolerance of LJCY by fructose metabolism while enhancing the drought tolerance of ZC108 by promoting glucan biosynthesis and galactose metabolism. Furthermore, the differential abundance phosphoproteins (DAPPs) related to intracellular protein transmembrane transport and protein transmembrane transport were enriched in LJCY, and the regulation of response to osmotic stress and regulation of mRNA processing were enriched in ZC108. In addition, protein-phosphoprotein interactions (PPI) analyses suggested that energy metabolism and starch and sucrose metabolic processes might play critical roles in LJCY and ZC108, respectively. These results will help to understand the mechanisms by which Z-3-HAC enhances the drought resistance of tea plants at the protein level. SIGNIFICANT: Green leaf volatiles (GLVs) are important volatile organic compounds that play essential roles in plant defense against biotic and abiotic stresses. To understand the mechanisms of Z-3-HAC in improving the drought tolerance of tea plants, two contrasting drought tolerance varieties (LJCY and ZC108) were comparatively evaluated by proteomics and phosphoproteomics. This analysis evidenced changes in the abundance of proteins involved in energy metabolism and starch and sucrose metabolic processes in LJCY and ZC108, respectively. These proteins may elucidate new molecular aspects of the drought resistance mechanism of Z-3-HAC, providing a theoretical basis for drought resistance breeding of tea plants.

Drought-Induced miRNA Expression Correlated with Heavy Metal, Phenolic Acid, and Protein and Nitrogen Levels in Five Chickpea Genotypes

Drought is a prime stress, drastically affecting plant growth, development, and yield. Plants have evolved various physiological, molecular, and biochemical mechanisms to cope with drought. Investigating specific biochemical pathways related to drought tolerance mechanisms of plants through biotechnology approaches is one of the quickest and most effective strategies for enhancing crop production. Among them, microRNAs (miRNAs) are the principal post-transcriptional regulators of gene expression in plants during plant growth under biotic and abiotic stresses. In this study, five different chickpea genotypes (İnci, Hasan bey, Arda, Seçkin, and Diyar 95) were grown under normal and drought stress. We recorded the expression levels of microRNAs in these genotypes and found differential expression (miRNA396, miR408, miRNA414, miRNA528, and miRNA1533) under contrasting conditions. Results revealed that miRNA414 and miRNA528 considerably increased in all genotypes under drought stress, and expression levels of miRNA418, miRNA1533, and miRNA396 (except for the Seçkin genotype) were found to be higher under the watered conditions. These genotypes were also investigated for heavy metal, phenolic acid, protein, and nitrogen concentrations under normal and drought stress conditions. The Arda genotype showed a significant increase in nitrogen (5.46%) and protein contents (28.3%), while protein contents were decreased in the Hasan bey and Seçkin genotypes subjected to drought stress. In the case of metals, iron was the most abundant element in all genotypes (İnci = 15.4 ppm, Hasan bey = 29.6 ppm, Seçkin = 37.8 ppm, Arda = 26.3 ppm, and Diyar 95 = 40.8 ppm) under normal conditions. Interestingly, these results were related to miRNA expression in the chickpea genotypes and hint at the regulation of multiple pathways under drought conditions. Overall, the present study will help us to understand the miRNA-mediated regulation of various pathways in chickpea genotypes.

Drought resistance index screening and evaluation of lettuce under water deficit conditions on the basis of morphological and physiological differences

Introduction

Water is one of the important factors affecting the yield of leafy vegetables. Lettuce, as a widely planted vegetable, requires frequent irrigation due to its shallow taproot and high leaf evaporation rate. Therefore, screening drought-resistant genotypes is of great significance for lettuce production.

Methods

In the present study, significant variations were observed among 13 morphological and physiological traits of 42 lettuce genotypes under normal irrigation and water-deficient conditions.

Results

Frequency analysis showed that soluble protein (SP) was evenly distributed across six intervals. Principal component analysis (PCA) was conducted to transform the 13 indexes into four independent comprehensive indicators with a cumulative contribution ratio of 94.83%. The stepwise regression analysis showed that root surface area (RSA), root volume (RV), belowground dry weight (BDW), soluble sugar (SS), SP, and leaf relative water content (RWC) could be used to evaluate and predict the drought resistance of lettuce genotypes. Furthermore, the drought resistance ranks of the genotypes were similar according to the drought resistance comprehensive evaluation value (D value), comprehensive drought resistance coefficient (CDC), and weight drought resistance coefficient (WDC). The cluster analysis enabled the division of the 42 genotypes into five drought resistance groups; among them, variety Yidali151 was divided into group I as a strongly drought-resistant variety, group II included 6 drought-resistant genotypes, group III included 16 moderately drought-resistant genotypes, group IV included 12 drought-sensitive genotypes, and group V included 7 highly drought-sensitive genotypes. Moreover, a representative lettuce variety was selected from each of the five groups to verify its water resistance ability under water deficit conditions. In the drought-resistant variety, it was observed that stomatal density, superoxide anion (O2.-wfi2) production rate, and malondialdehyde (MDA) content exhibited a low increase rate, while catalase (CAT), superoxide dismutase (SOD), and that peroxidase (POD) activity exhibited a higher increase than in the drought-sensitive variety.

Discussion

In summary, the identified genotypes are important because their drought-resistant traits can be used in future drought-resistant lettuce breeding programs and water-efficient cultivation.

Evaluation of yield attributes and bioactive phytochemicals of twenty amaranth genotypes of Bengal floodplain

Twenty vegetable amaranth (VA) genotypes were evaluated to assess the variability, associations, path coefficient, and principal component analysis (PCA) of morpho-chemical traits. The genotypes exhibited adequate antioxidant colorants, phytochemicals, and antiradical capacity with significant variations across genotypes. Genetic parameters revealed selection criteria for the majority of the traits for improving amaranth foliage yield (FY). Based on correlation coefficient, stem weight, stem base diameter, root weight, plant height, and shoot weight for significant development of FY of VA. Observing significant genotypic correlation with high positive direct effects on FY, the path coefficient (PC) of root weight, stem base diameter, stem weight, and shoot weight could contribute to the noteworthy development of FY of VA. The genotypes AA5, AA6, AA8, AA10, AA11, AA19, and AA20 might be selected for high FY, antioxidant colorants, and antiradical phytochemicals to utilize as colorants and antiradical rich superior high yielding cultivars. The first PC accounted for 37.8% of the variances, which implies a larger proportion of variable information explained by PC1. The features that contributed more to PC1 were FY, SW, STW, RW, and PH, whereas Chl b, total Chl, and Chl a contributed to the second PC. This suggests that there are significant genetic differences between amaranths in terms of biochemical and agro-morphological characteristics. The findings of the current work support plant breeders to investigate the genetic potential of the amaranth germplasm, notably in biochemical parameters. High colorants enrich genotypes that can be selected for extracting natural colorants to use in food processing industries.

Modulation of ethylene and ROS-scavenging enzymes by multifarious plant growth-promoting endophytes in tomato (Solanum lycopersicum) plants to combat Xanthomonas -induced stress

The purpose of the current study was to explore root endophytes- Priestia megaterium T3 and Bacillus cereus T4 from Moringa olefiera for the suppression of leaf spot disease in tomato plants challenged with Xanthomonas vesicatoria. Both strains had plant growth-stimulating characteristics including auxin production, solubilization of inorganic phosphate and zinc complexes, and production of ammonia, siderophore, as well as hydrolytic enzymes. An agar well diffusion and fluorescence viability assay have validated the antibacterial effect of the cell-free culture supernatant of strains T3 and T4. Liquid chromatography-mass spectrometry (LC-MS) profiling has identified the secondary metabolites in the cell-free supernatant of strains T3 and T4. The bio-priming of tomato seeds with a consortium of T3 and T4 strains has significantly declined ethylene (by 0.61-fold) and hydrogen peroxide (H2O2, 0.64-fold) concentration thus, maintaining a lower content of ROS-induced malondialdehyde (MDA, 0.91-fold) as compared to control counterparts. Consequently, the leaf spot disease severity was reduced by ∼70% in consortium-treated tomato plants in contrast to their pathogen-challenged control. The consortia (T3+T4) treatment has facilitated induced systemic resistance by enhancing enzymatic activities of phenylalanine ammonia-lyase (PAL), peroxidase (PO), polyphenol oxidase (PPO), catalase (CAT), and ascorbate oxidase (AO) to detoxify the excessive Xanthomonas-induced ROS accumulation in tomato plants. Conclusively, bacterial endophytes modulate X. vesicatoria-induced ROS response and ethylene levels in tomato plants. The current findings indicate that plant growth-promoting endophytic bacterial strains hold the potential to sustainably enhance plant growth and suppress bacterial leaf spot disease in tomato plants.

Effectiveness of silver nitrate application on plant growth and bioactive compounds in Agastache rugosa (Fisch. & C.A.Mey.) kuntze

The objective of this study was to determine the optimal dose of silver nitrate (AgNO3) for plant growth and to increase the main bioactive compounds in A. rugosa cultivated in a hydroponic system. The application of soaked diniconazole (120 μmol mol-1) to all plants at 7 days after transplanting (DAT) for dwarfing plant height, optimizing cultivation space in the plant factory. Subsequently, plants were soaked with 50, 100, 200, and 400 μmol mol-1 AgNO3 for 10 min at 25 DAT and harvested at 39 DAT. The results indicated that 200 and 400 μmol mol-1 treatments tended to severely decrease plant growth parameters compared to treatments with lower concentrations. The net photosynthetic rate was significantly reduced by the 200 and 400 μmol mol-1 treatments compared to treatments with other concentrations. The 400 μmol mol-1 treatment led to the lowest concentrations of chlorophyll a, chlorophyll a/b, total carotenoid, chlorophyll b, and the total chlorophyll. However, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity was considerably increased in 50, 100, 200, and 400 μmol mol-1 compared to that of the control plants. A higher rosmarinic acid (RA) concentration in the whole plant was noticed with the 400 μmol mol-1 treatment compared with that of the untreated plants. The 100 μmol mol-1 treatment exhibited the highest concentration and content of tilianin in the whole plant. Concentration of acacetin 1 significantly increased in the whole plant with 100 and 200 μmol mol-1 treatments compared with that of the untreated plants. Concentrations of acacetin 2 and 3 in the whole plant were the highest with 100 and 200 μmol mol-1 treatments, respectively. The results demonstrated that 100 μmol mol-1 treatments can be used to increase bioactive compounds without severely limiting the plant growth and reducing chlorophyll concentrations of A. rugosa. Implementing this optimal dose can enable growers and researchers to cultivate A. rugosa more efficiently, enhancing bioactive compound content and overall plant performance, thus harnessing the potential health benefits of this valuable plant species.

Effect of exogenous taurine on growth, oxidative defense, and nickel (Ni) uptake in canola (Brassica napus L.) under Ni stress

Nickel (Ni) contamination and its associated hazardous effects on human health and plant growth are ironclad. However, the potential remedial effects of taurine (TAU) on Ni-induced stress in plants remain obscure. Therefore, the present study was undertaken to examine the effect of TAU seed priming (100 and 150 mg L‒1) as an alleviative strategy to circumvent the phytotoxic effects of Ni (150 mg kg‒1) on two canola cultivars (Ni-tolerant cv. Shiralee and Ni-sensitive cv. Dunkeld). Our results manifested an apparent decline in growth, biomass, photosynthetic pigments, leaf relative water content, DPPH free radical scavenging activity, total soluble proteins, nitrate reductase activity, and nutrient acquisition (N, P, K, Ca) under Ni toxicity. Further, Ni toxicity led to a substantial increase in oxidative stress reflected as higher levels of superoxide radicals (O2•‒) and hydrogen peroxide (H2O2) alongside increased relative membrane permeability, lipoxygenase (LOX) activity, and Ni accumulation in leaves and roots. However, TAU protected canola plants from Ni-induced oxidative damage through the amplification of hydrogen sulfide (H2S) production that intensified the antioxidant system to avert O2•‒, H2O2, and malondialdehyde (MDA) production. Further, TAU-mediated increase in H2S levels maintained membrane integrity that might have improved ionomics and bettered plant growth under Ni toxicity.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-023-01359-9.

Enhanced Physiological and Biochemical Performance of Mung Bean and Maize under Saline and Heavy Metal Stress through Application of Endophytic Fungal Strain SL3 and Exogenous IAA

Modern irrigation practices and industrial pollution can contribute to the simultaneous occurrence of salinity and heavy metal contamination in large areas of the world, resulting in significant negative effects on crop productivity and sustainability. This study aimed to investigate the growth-promoting potentials of an important endophytic fungal strain SL3 and to compare its potential with exogenous IAA (indole-3-acetic acid) in the context of salt and heavy metal stress. The strain was assessed for plant growth-promoting traits such as the production of indole-3-acetic acid, gibberellins (GA), and siderophore. We selected two important crops, mung bean and maize, and examined various physiological and biochemical characteristics under 300 mM NaCl and 2.5 mM Pb stress conditions, with and without the application of IAA and SL3. This study's results demonstrated that both IAA and SL3 positively impacted the growth and development of plants under normal and stressed conditions. In NaCl and Pb-induced stress conditions, the growth of mung bean and maize plants was significantly reduced. However, the application of IAA and SL3 helped to alleviate stress, leading to a significant increase in shoot/root length and weight compared to IAA and SL3 non-treated plants. The results revealed that photosynthetic pigments, accumulation of catalase (CAT), phenolic contents, polyphenol oxidase, and flavanols are higher in the IAA and SL3-treated plants than in the non-inoculated plants. This study's findings revealed that applying the SL3 fungal strain positively influenced various physiological and biochemical processes in tested plant species under normal and stress conditions of NaCl and Pb. These findings also suggested that SL3 could be a potential replacement for widely used IAA to promote plant growth by improving photosynthetic efficiency, reducing oxidative stress, and enhancing metabolic activities in plants, including mung and maize. Moreover, this study highlights that SL3 has synergistic effects with IAA in enhancing resilience to salt and heavy stress and offers a promising avenue for future agricultural applications in salt and heavy metal-affected regions.

Water-Deficit Stress in the Epiphytic Elkhorn Fern: Insight into Photosynthetic Response

Progressive climate changes cause disturbance of water relations in tropical rainforests, where epiphytic ferns are an important element of biodiversity. In these plants, the efficiency of photosynthesis is closely related to the efficiency of water transport. In addition, due to the lack of contact with the soil, epiphytes are extremely susceptible to water-deficit stress. The aim of this experiment was to determine the response of the photosynthetic apparatus of Platycerium bifurcatum to a 6-week water deficit. The hydration and pigment composition of leaves were determined using reflectance spectroscopy and epifluorescence microscopy. Chlorophyll a fluorescence kinetics parameters, fluorescence induction curves (OJIP), low-temperature fluorescence curves at 77 K and proline concentration were analyzed at seven time points. After a decrease in leaf hydration by 10-15%, there were disturbances in the oxidation-reduction balance, especially in the initial photochemical reactions, a rapid decrease in plant vitality (PI) and significant fluctuations in chlorophyll a fluorescence parameters. The relative size of PSI antenna structures compared to PSII decreased in the following weeks of water deficit. Changes in photochemical reactions were accompanied by a decrease in gross photosynthesis and an increase in proline concentration. Changes in the functioning of photosynthesis light phase and the pigment composition of leaves are related to the resistance of elkhorn fern to long-term water deficit.

Modulation of Antioxidant Compounds in Fruits of Citrus reticulata Blanco Using Postharvest LED Irradiation

Phlegrean mandarin fruits are already known for health-promoting properties due to the high concentration of phytochemicals in peel, pulp, and seed. Biotic and abiotic factors, including light, may modulate their biosynthesis, metabolism, and accumulation. In this context, light-emitting diodes (LED) have recently been applied to control nutritional traits, ripening process, senescence, fruit shelf-life, and pathogenic microbial spoilage of fruits. This study investigated the effect of the seven-day exposure of Phlegrean mandarin fruits to two LED regimes, white (W) and red-blue (RB), to test the possibility that the storage under specific light wavelengths may be used as green preservation technology that enhances fruit phytochemical properties. To pursue this aim, the antioxidant activity and polyphenolic profile of the pulp and peel of mandarins under W and RB light regimes were evaluated and compared with Control fruits not exposed to LED treatment. Our results indicated that storage under W and RB treatments modulates the antioxidant content in pulp and peel differently. Compared to W, the RB regime increases the ascorbic acid, flavonoid, anthocyanin, and carotenoid concentrations, while the polyphenol profile analysis reveals that the number of important phytochemicals, i.e., quercetin rutinoside, chlorogenic acid, sinensetin, and rutin, are higher under W. The overall data demonstrated that postharvest LED irradiation is a valid tool for modifying fruit phytochemical properties, which also boosts specific bioactive compounds.

Essential oil-grafted copper nanoparticles as a potential next-generation fungicide for holistic disease management in maize

Sustainable food production is necessary to meet the demand of the incessantly growing human population. Phytopathogens pose a major constraint in food production, and the use of conventional fungicides to manage them is under the purview of criticism due to their numerous setbacks. In the present study, essential oil-grafted copper nanoparticles (EGC) were generated, characterized, and evaluated against the maize fungal pathogens, viz., Bipolaris maydis, Rhizoctonia solani f. sp. sasakii, Macrophomina phaseolina, Fusarium verticillioides, and Sclerotium rolfsii. The ED₅₀ for the fungi under study ranged from 43 to 56 μg ml^-1, and a significant inhibition was observed at a low dose of 20 μg ml^-1 under in vitro conditions. Under net house conditions, seed treatment + foliar spray at 250 and 500 mg L^-1 of EGC performed remarkably against maydis leaf blight (MLB), with reduced percent disease index (PDI) by 27.116 and 25.292%, respectively, in two Kharif seasons (May-Sep, 2021, 2022). The activity of enzymatic antioxidants, viz., β-1, 3-glucanase, PAL, POX, and PPO, and a non-enzymatic antioxidant (total phenolics) was increased in treated maize plants, indicating host defense was triggered. The optimum concentrations of EGC (250 mg L^-1 and 500 mg L^-1) exhibited improved physiological characteristics such as photosynthetic activity, shoot biomass, plant height, germination percentage, vigor index, and root system traits. However, higher concentrations of 1,000 mg L^-1 rendered phytotoxicity, reducing growth, biomass, and copper bioaccumulation to high toxic levels, mainly in the foliar-sprayed maize leaves. In addition, EGC and copper nanoparticles (CuNPs) at 1,000 mg L^-1 reduced the absorption and concentration of manganese and zinc indicating a negative correlation between Cu and Mn/Zn. Our study proposes that the CuNPs combined with EO (Clove oil) exhibit astounding synergistic efficacy against maize fungal pathogens and optimized concentrations can be used as an alternative to commercial fungicides without any serious impact on environmental health.

Biostimulant red seaweed (Gracilaria tenuistipitata var. liui) extracts spray improves yield and drought tolerance in soybean

Drought has a deleterious impact on the growth, physiology, and yield of various plants, including soybean. Seaweed extracts are rich in various bioactive compounds, including antioxidants, and can be used as biostimulants for improving yield and alleviating the adverse effect of drought stress. The purpose of this study was to evaluate the effect of soybean growth and yield with different concentrations (0.0%, 5.0%, and 10.0% v/v) of water extracts of the red seaweed Gracilaria tenuistipitata var. liui under well-watered (80% of field capacity (FC) and drought (40% of FC)) conditions. Drought stress decreased soybean grain yield by 45.58% compared to well-watered circumstances but increased the water saturation deficit by 37.87%. It also decreased leaf water, chlorophyll content, plant height, and the fresh weight of the leaf, stem, and petiole. Drought stress decreased soybean grain yield by 45.58% compared to well-watered circumstances but increased the water saturation deficit by 37.87%. It also decreased leaf water, chlorophyll content, plant height, and the fresh weight of the leaf, stem, and petiole. Under both drought and well-watered situations, foliar application of seaweed extracts dramatically improved soybean growth and production. Under drought and well-watered situations, 10.0% seaweed extract increased grain yield by 54.87% and 23.97%, respectively in comparison to untreated plants. The results of this study suggest that red seaweed extracts from Gracilaria tenuistipitata var. liui may be used as a biostimulant to improve soybean yield and drought tolerance in the presence of insufficient water. However, the actual mechanisms behind these improvements need to be further investigated in field conditions.

StMAPK1 functions as a thermos-tolerant gene in regulating heat stress tolerance in potato (Solanum tuberosum)

Background and aims

Mitogen-activated protein kinases (MAPKs) have been reported to respond to various stimuli including heat stress. This research aimed to investigate whether StMAPK1 is implicated in the transduction of the heat stress signal to adapt heat stress as a thermos-tolerant gene.

Materials and methods

Potato plants were cultivated under mild (30°C) and acute (35°C) heat stress conditions to analyze mRNA expression of StMAPKs and physiological indicators. StMAPK1 was up-regulated and down-regulated by transfection. Subcellular localization of StMAPK1 protein was observed by fluorescence microscope. The transgenic potato plants were assayed for physiological indexes, photosynthesis, cellular membrane integrity, and heat stress response gene expression.

Results

Heat stress altered the expression prolife of StMAPKs. StMAPK1 overexpression changed the physiological characteristics and phenotypes of potato plants under heat stresses. StMAPK1 mediates photosynthesis and maintains membrane integrity of potato plants in response to heat stress. Stress response genes (StP5CS, StCAT, StSOD, and StPOD) in potato plants were altered by StMAPK1 dysregulation. mRNA expression of heat stress genes (StHSP90, StHSP70, StHSP20, and StHSFA3) was affected by StMAPK1.

Conclusions

StMAPK1 overexpression increases the heat-tolerant capacity of potato plants at the morphological, physiological, molecular, and genetic levels.

Evaluation of Legume-Rhizobial Symbiotic Interactions Beyond Nitrogen Fixation That Help the Host Survival and Diversification in Hostile Environments

Plants often experience unfavorable conditions during their life cycle that impact their growth and sometimes their survival. A temporary phase of such stress, which can result from heavy metals, drought, salinity, or extremes of temperature or pH, can cause mild to enormous damage to the plant depending on its duration and intensity. Besides environmental stress, plants are the target of many microbial pathogens, causing diseases of varying severity. In plants that harbor mutualistic bacteria, stress can affect the symbiotic interaction and its outcome. To achieve the full potential of a symbiotic relationship between the host and rhizobia, it is important that the host plant maintains good growth characteristics and stay healthy under challenging environmental conditions. The host plant cannot provide good accommodation for the symbiont if it is infested with diseases and prone to other predators. Because the bacterium relies on metabolites for survival and multiplication, it is in its best interests to keep the host plant as stress-free as possible and to keep the supply stable. Although plants have developed many mitigation strategies to cope with stress, the symbiotic bacterium has developed the capability to augment the plant's defense mechanisms against environmental stress. They also provide the host with protection against certain diseases. The protective features of rhizobial-host interaction along with nitrogen fixation appear to have played a significant role in legume diversification. When considering a legume-rhizobial symbiosis, extra benefits to the host are sometimes overlooked in favor of the symbionts' nitrogen fixation efficiency. This review examines all of those additional considerations of a symbiotic interaction that enable the host to withstand a wide range of stresses, enabling plant survival under hostile regimes. In addition, the review focuses on the rhizosphere microbiome, which has emerged as a strong pillar of evolutionary reserve to equip the symbiotic interaction in the interests of both the rhizobia and host. The evaluation would draw the researchers' attention to the symbiotic relationship as being advantageous to the host plant as a whole and the role it plays in the plant's adaptation to unfavorable environmental conditions.

Potential application of melatonin in reducing boron toxicity in rice seedlings through improved growth, cell wall composition, proline, and defense mechanisms

Melatonin (MT) has been demonstrated to provide defense against both biotic and abiotic stressors. Boron toxicity (BT) can significantly limit the growth and production of plants. However, few studies have been conducted on whether MT is effective in attenuating B toxicity in different plants. In order to evaluate the efficacy of exogenous MT treatment in reducing the negative impact of BT on rice seedlings, this study examined the influence of MT on growth, antioxidant capacity, cell wall composition, and proline metabolism in rice seedlings under hydroponics. Four treatments were established: MT (50 μM), MT + BT (50 μM MT + 800 μM B), BT (800 μM), and CK (control) in a completely randomized design. The results indicate that BT had a significant detrimental effect on the shoot length, root length, and root and shoot fresh weights of rice seedlings by 11.96%, 27.77%, 25.69%, and 18.67%, respectively as compared to the control treatment. However, exogenous MT application increased these parameters and reduced B accumulation in aboveground parts (14.05%) of the plant. Exogenous MT also increased the endogenous melatonin content and antioxidant enzyme activities (64.45%, 71.61%, 237.64%, and 55.42% increase in superoxide dismutase, ascorbate peroxidase, and peroxidase activities, respectively), while decreasing reactive oxygen species levels and oxidized forms of glutathione and ascorbic acid. Additionally, MT enhanced the biosynthesis of proline by decreasing proline dehydrogenase (ProDH) and increasing the GSH (glutathione) and ASA (ascorbic acid) contents. Exogenous MT also increased cell wall components that can increase B adsorption to the cell wall. Overall, these findings suggest that MT application can be a potential solution for strengthening the stress tolerance of rice seedlings, particularly under conditions of B toxicity. In regions where soil contains high levels of boron, the use of MT could enhance rice crop yields and quality.

Assessing the role of ACC deaminase-producing bacteria in alleviating salinity stress and enhancing zinc uptake in plants by altering the root architecture of French bean (Phaseolus vulgaris) plants

MAIN CONCLUSION

The consortium inoculation with strains R1 and R4 modified the root system to boost seedling growth, increase the zinc content of French bean pods, and reduce salinity stress. The present study demonstrated the effect of two 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase-producing plant growth-promoting rhizobacteria (Pantoea agglomerans R1 and Pseudomonas fragi R4) alone and consortia on the root system development, French bean growth, and zinc content as well as salinity stress tolerance. Both the strains were characterized for ACC utilization activity (426.23 and 380.54 nmol α-ketobutyrate mg protein^-1 h^-1), indole acetic acid (IAA) production, phosphate solubilization, ammonia, hydrogen cyanide (HCN), and siderophore production. The strains exhibited zinc solubilization in both plate and broth assays with zinc oxide and zinc carbonate as zinc sources as validated by atomic absorption spectroscopy (AAS). Single or combined inoculations with the selected strains significantly modulated the architectural and morphological traits of the root system of French bean plants. Furthermore, the application of R1and R4 consortia has enhanced zinc content in roots (60.83 mg kg^-1), shoots (15.41 mg kg^-1), and pods (30.04 mg kg^-1) of French bean plants grown in ZnCO₃ amended soil. In another set of pot experiments, the consortium bacterization has significantly enhanced length as well as fresh and dry biomass of roots and shoots of the French bean plant under saline stress conditions. Additionally, inoculation with ACC-degrading rhizobacterial strains has increased chlorophyll and carotenoid contents, osmoprotectant content, and antioxidative enzyme (catalase and peroxidase) activity in comparison to their counterparts exposed to salt treatments only. Current findings suggested ACC deaminase-producing rhizobacterial strains hold the potential to improve root architecture which in turn promotes plant growth under salt-stressed conditions as well as enhances micronutrient concentration in host plants.

Transcriptome and metabolome analysis reveals key genes and secondary metabolites of Casuarina equisetifolia ssp. incana in response to drought stress

Casuarina equisetifolia is drought tolerant, salt tolerant, and able to grow in barren environments. It is often used to reduce wind damage, to prevent sand erosion, and to help establish plant communities in tropical and subtropical coastal zones. To determine the basis for its drought tolerance, we conducted transcriptomic and metabolic analyses of young branchlets under a non-drought treatment (D_0h) and 2-, 12-, and 24-h-long drought treatments (D_2h, D_12h, and D_24h). A total of 5033 and 8159 differentially expressed genes (DEGs) were identified in D_2h/D_0h and D_24h/D_0h. These DEGs were involved in plant hormone signal transduction, jasmonic acid (JA) biosynthesis, flavonoid biosynthesis, and phenylpropanoid biosynthesis. A total of 148 and 168 differentially accumulated metabolites (DAMs) were identified in D_12h/D_0h and D_24h/D_0h, which were mainly amino acids, phenolic acids, and flavonoids. In conclusion, C. equisetifolia responds to drought by regulating plant hormone signal transduction and the biosynthesis of JA, flavonoid, and phenylpropanoid. These results increase the understanding of drought tolerance in C. equisetifolia at both transcriptional and metabolic levels and provide new insights into coastal vegetation reconstruction and management.

Potential Role of Biochar and Silicon in Improving Physio-Biochemical and Yield Characteristics of Borage Plants under Different Irrigation Regimes

Silicon (Si) and biochar (Bc) are key signaling conditioners that improve plant metabolic processes and promote drought tolerance. However, the specific role of their integrative application under water restrictions on economical plants is not yet well understood. Two field experiments throughout 2018/2019 and 2019/2020 were conducted to examine the physio-biochemical modifications and yield attributes of borage plants mediated by Bc (9.52 tons ha^-1) and/or Si (300 mg L^-1) under different irrigation regimes (100, 75, and 50% of crop evapotranspiration). Catalase (CAT) and peroxidase (POD) activity; relative water content, water, and osmotic potential; leaf area per plant and yield attributes; and chlorophyll (Chl) content, Chl_a/chlorophyllide_a (Chlid_a), and Chl_b/Chlid_b were considerably reduced within the drought condition. On the other hand, oxidative biomarkers, as well as organic and antioxidant solutes, were increased under drought, associated with membrane dysfunction, superoxide dismutase (SOD) activation, and osmotic adjustment (OA) capacity as well as a hyperaccumulation of porphyrin intermediates. Supplementation of Bc and Si lessens the detrimental impacts of drought on several plant metabolic processes associated with increasing leaf area and yield attributes. Their application under normal or drought conditions significantly elicited the accumulation of organic and antioxidant solutes as well as the activation of antioxidant enzymes, followed by lessening the formation of free radical oxygen and mitigating oxidative injuries. Moreover, their application maintained water status and OA capacity. Si and/or Bc treatment reduced protoporphyrin, magnesium-protoporphyrin, and protochlorophyllide while increasing Chl_a and Chl_b assimilation and boosting the ratio of Chl_a/Chlid_a and Chl_b/Chlid_b, resulting in a rise in leaf area per plant and yield components following these modifications. These findings highlight the significance of Si and/or Bc as (a) stress-signaling molecule(s) in regulating defensive systems in drought-affected borage plants by boosting antioxidant aptitude, regulating water status, and accelerating chlorophyll assimilation, thus leading to increasing leaf area and productivity.

Physiological, biochemical and molecular responses associated with drought tolerance in grafted grapevine

BACKGROUND

Grafting is one of the promising techniques for improving abiotic stress tolerance in horticultural crops, but the underlying regulatory mechanisms of drought on grafted grapevine are largely unexplored.

RESULTS

Herein, we investigated the phenotypic, physiologic, biochemical, and drought related genes change of self-rooted 1103P (1103 Paulsen), SM (Shine Muscat) and grafted SM/1103P (SM shoot/1103P root) under drought stress condition. The results indicated that grafted grapevine effectively alleviated drought damage in grape leaves by higher RWC, water potential and free water content. Drought stress led to the alterations of chlorophyll, carotenoid, photosynthetic parameters and chlorophyll fluorescence in grapevine leaves after drought treatment indicated grafted plants improved the photosystem response to drought stress. Moreover, grafted plants under drought stress exhibited higher levels of abscisic acid (ABA), indoleacetic acid (IAA) and soluble protein, but less contents of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) both in leaves and roots. Drought stress also increased the activities of antioxidant enzymes (SOD, POD and CAT) and activated the transcript expression of VvCu/ZnSOD, VvPOD4 and VvCAT1) in both leaves and roots. Further expression analysis by real-time PCR indicated that the expression levels of ABA-dependent and ABA-independent related genes could be activated in grafted grape after drought treatment.

CONCLUSIONS

Taken together, our findings demonstrated that grafting onto 1103P enhanced tolerance against drought stress in grape by improving water content, photosynthesis and antioxidant defense capacity, which provided a valuable information for understanding the mechanisms of drought tolerance regulated by grafting plants.

Physiological and biochemical changes in Moroccan barley (Hordeum vulgare L.) cultivars submitted to drought stress

Barley (Hordeum vulgare L.) is the second most consumed and cultivated cereal by the Moroccan population. However, it is predicted that frequent drought periods, caused by climate change, can cause problems in plant growth. Thus, the selection of drought-tolerant barley cultivars is essential to ensure the security of barley's needs. We aimed to screen drought stress tolerance in Moroccan barley cultivars. We tested the drought tolerance of nine Moroccan barley cultivars ('Adrar', 'Amalou', 'Amira', 'Firdaws', 'Laanaceur', 'Massine', 'Oussama', 'Taffa', and 'Tamellalt') based on physiological and biochemical parameters. Drought stress was applied by maintaining field capacity at 40% (90% for the control), and plants were randomly arranged in a greenhouse at 25 °C under natural light conditions. Drought stress decreased relative water content (RWC), shoot dry weight (SDW), and chlorophyll content (SPAD index), but significantly increased electrolyte leakage, hydrogen peroxide, malondialdehyde (MDA), water-soluble carbohydrates, and soluble protein contents, as well as catalase (CAT) and ascorbate peroxidase (APX) activities. High levels of SDW, RWC, CAT, and APX activities were recorded in 'Firdaws', 'Laanaceur', 'Massine', 'Taffa', and 'Oussama', which can be interpreted by high drought tolerance. On the other hand, 'Adrar', 'Amalou', 'Amira', and 'Tamellalt' showed higher values of MDA and H₂O₂ content, which can be linked with drought sensitivity. Physiological and biochemical parameter changes are discussed in terms of barley's tolerance to drought. Tolerant cultivars could be a good background for barley breeding in areas known for the alternative of long dry spells.

Salinity Stress Ameliorates Pigments, Minerals, Polyphenolic Profiles, and Antiradical Capacity in Lalshak

Previous studies have shown that salinity eustress enhances the nutritional and bioactive compounds and antiradical capacity (ARC) of vegetables and increases the food values for nourishing human diets. Amaranth is a salinity-resistant, rapidly grown C4 leafy vegetable with diverse variability and usage. It has a high possibility to enhance nutritional and bioactive compounds and ARC by the application of salinity eustress. Hence, the present study aimed to evaluate the effects of sodium chloride stress response in a selected Lalshak (A. gangeticus) genotype on minerals, ascorbic acid (AsA), Folin−Ciocalteu reducing capacity, beta-carotene (BC), total flavonoids (TF), pigments, polyphenolic profiles, and ARC. A high-yield, high-ARC genotype (LS6) was grown under conditions of 0, 25, 50, and 100 mM sodium chloride in four replicates following a block design with complete randomization. We recognized nine copious polyphenolic compounds in this accession for the first time. Minerals, Folin−Ciocalteu reducing capacity, AsA, BC, pigments, polyphenolic profiles, and ARC of Lalshak were augmented progressively in the order: 0 < 25 < 50 < 100 mM sodium chloride. At 50 mM and 100 mM salt concentrations, minerals, AsA, Folin−Ciocalteu reducing capacity, BC, TF, pigments, polyphenolic profiles, and ARC of Lalshak were much greater than those of the control. Lalshak could be used as valuable food for human diets as a potent antioxidant. Sodium chloride-enriched Lalshak provided outstanding quality to the final product in terms of minerals, AsA, Folin−Ciocalteu reducing capacity, BC, TF, pigments, polyphenolic profiles, and ARC. We can cultivate it as a promising alternative crop in salinity-prone areas of the world.

Superoxide dismutase (SOD) family in durum wheat: promising candidates for improving crop resilience

The SOD family has been extensively analyzed at genome wide level in several crops. However, little is known about this family in durum wheat. In this study, a total of 14 TdSOD genes were identified in whole durum wheat genome including 8 TdCu-ZnSODs, 2 TdMnSODs, and 4 TdFeSODs. In silico analysis evinced that TdSOD family members displayed a closer evolutionary relationship, similar gene structure and protein features with their homologs from other plant species. Furthermore, the analysis of their promoter regions revealed the presence of a great number of cis-regulatory elements related to plant development, abiotic and biotic stresses, phytohormones, and several potential binding sites for transcription factors. Interestingly, 3D structure analysis revealed that TdCu-ZnSOD2A-2 and TdCu-ZnSOD2B-2, belonging to the Cu-Zn group, were modeled as copper chaperone for SOD like their homologs from rice and Arabidopsis. The expression profile of eight TdSOD candidate genes was investigated under salt, drought, cold, and ABA treatments. Notably, TdCu-ZnSOD2A-1, TdFeSOD4A-1, and TdFeSOD7A-1 were significantly up-regulated under all stress treatments. On the other hand, TdCu-ZnSOD7B and TdMnSOD2B were strongly expressed in roots and leaves under cold stress and TdCu-ZnSOD2B-2 was particularly up-regulated in leaves under ABA treatment. Ultimately, these findings provide valuable information for the identification of attractive candidate genes to improve wheat resilience.

Influence of foliar spray and post-harvest treatments on head yield, shelf-life, and physicochemical qualities of broccoli

Rapid senescence is the key factor in the deterioration of post-harvest shelf-life in broccoli heads. This study evaluates the head yield and its related traits, and physicochemical attributes of broccoli under four foliar sprays of mineral nutrients (B, Zn, Mo, and B + Zn + Mo) with control. The interaction effects of shelf-life and physicochemical attributes of broccoli for these five pre-harvest and five post-harvest storage treatments (LDP bag, HDP vacuum pack, 2% eggshell powder solution, 2% ascorbic acid, and control) both at cold storage and room temperature were evaluated with three replications. The significantly higher marketable head yield of 28.02 t ha^-1, maximum gross return [(Bangladesh Taka (BDT 420300 ha^-1)], net return (BDT 30565 ha^-1), and maximum benefit-cost ratio (BCR) of 3.67 were obtained from the pre-harvest foliar application of B + Zn + Mo in broccoli. Pre-harvest foliar spray of combined nutrient B + Zn + Mo and post-harvest treatment high-density polyethylene (HDP, 15 μm) vacuum packaging efficiently improve post-harvest physicochemical attributes, viz., compactness, green color, texture, carbohydrates, fats, energy, antioxidants, vitamin C, and total phenols in broccoli head compared to the rest of the treatment combinations. In addition, this treatment combination also confirmed a maximum shelf-life of 24.55 days at cold storage [relative humidity (RH) 90-95% and 4°C] and 7.05 days at room temperature (RH 60-65% and 14-22°C) compared to the rest of the treatment combinations. Therefore, we recommend a pre-harvest foliar spray of combined nutrient elements B + Zn + Mo and an HDP (15 μm) vacuum post-harvest packaging for the maximum benefits for both farmers and consumers to get the best head yield, anticipated physicochemical attributes, and maximum shelf-life of broccoli.

Exogenous application of melatonin to mitigate drought stress-induced oxidative damage in Phoebe sheareri seedlings

Background

Drought stress is a major prevalent environmental factor impairing growth. Melatonin mitigates the impacts of drought stress on plants. However, melatonin's role in Phoebe sheareri (Hemsl.) Gamble (P. sheareri) is unknown. We aimed to reveal the protective effects of melatonin on P. sheareri seedlings under drought conditions.

Methods

Melatonin was sprayed under drought or normal water conditions. The parameters, including growth, physiological factors, and phytohormones of P. sheareri, were examined.

Results

Compared to the normal control group, drought stress inhibited the growth of seedlings and significantly reduced the content of carotenoids, SOD, POD, APX, PPO, CAT, GR, and soluble sugars, and increased the contents of MDA, O₂ ^•-, proline, soluble proteins, ABA, and JA-Me in P. sheareri seedlings. However, melatonin treatment significantly reversed the adverse drought-induced responses and promoted the P. sheareri seedling's growth. Moreover, the heatmap and principal component analysis suggested a high similarity in the behavior patterns of the six measured antioxidant enzymes in P. sheareri seedlings.

Conclusion

Our study reported for the first time that melatonin has a protective role in P. sheareri seedlings under drought-stress conditions. This role is related to ROS scavenging, activation of antioxidant enzymes, and crosstalk of phytohormones. This study provided a theoretical basis for improving the ability of P. sheareri adapted to arid environments.

Heritable priming by Trichoderma: A sustainable approach for wheat protection against Bipolaris sorokiniana

Crop plants encounter a variety of biotic challenges in the field and faces significant reduction in crop yield. In the current scenario of an ever increasing global population, there is an urgent need to protect plant health by using sustainable approach to maximize the crop productivity and to mitigate the food demands. Nowadays, we mostly rely on chemical crop protection techniques, which are causing a number of environmental and health difficulties. Defence priming is a chemical-free, eco-friendly, and sustainable strategy of crop protection, which is also called "green vaccination. In the present study, for the first time, we used Trichoderma as a priming agent to protect wheat crop from spot blotch disease. We have established Trichoderma-mediated defence priming in wheat against Bipolaris sorokiniana for sustainable crop improvement. We have characterised the morphological, disease phenotype, biochemical and yield parameters of Trichoderma-primed and non-primed wheat under disease pressure. Trichoderma-primed plants were found to be more protected against B. sorokiniana as compared to non-primed plants. Biochemical studies indicated that there is no direct defence response after priming stimulus but the defence response was activated only after triggering stimulus in terms of enhanced defence metabolites in primed plants as compared to non-primed plants. In the present study, since defence was activated only when required, that is under disease pressure, there was no unnecessary allocation of resources towards defence. Hence, no yield penalty was shown in primed plants as compared to control. We further evaluated the inheritance of primed state to the next generation and found that progeny of primed parents also performed better than progeny of non-primed parents under disease pressure in terms of protection from B. sorokiniana as well as yield performance. This strategy has the potential to protect crop without any yield penalty and causing environmental degradation. Our research findings indicate that Trichoderma-mediated defence priming could be an alternative approach for improving wheat productivity under biotic stress. To be our best knowledge, this is the first documented report for the Trichoderma-mediated defence priming and induced inheritance in wheat plant. This study will open new arenas in sustainable crop protection strategies for the exploitation of defence priming in crop plants.

Salt Eustress Induction in Red Amaranth (Amaranthus gangeticus) Augments Nutritional, Phenolic Acids and Antiradical Potential of Leaves

Earlier researchers have highlighted the utilization of salt eustress for boosting the nutritional and phenolic acid (PA) profiles and antiradical potential (ARP) of vegetables, which eventually boost food values for nourishing human diets. Amaranth is a rapidly grown, diversely acclimated C4 leafy vegetable with climate resilience and salinity resistance. The application of salinity eustress in amaranth has a great scope to augment the nutritional and PA profiles and ARP. Therefore, the A. gangeticus genotype was evaluated in response to salt eustress for nutrients, PA profile, and ARP. Antioxidant potential and high-yielding genotype (LS1) were grown under four salt eustresses (control, 25 mM, 50 mM, 100 mM NaCl) in a randomized completely block design (RCBD) in four replicates. Salt stress remarkably augmented microelements, proximate, macro-elements, phytochemicals, PA profiles, and ARP of A. gangeticus leaves in this order: control < low sodium chloride stress (LSCS) < moderate sodium chloride stress (MSCS) < severe sodium chloride stress (SSCS). A large quantity of 16 PAs, including seven cinnamic acids (CAs) and nine benzoic acids (BAs) were detected in A. gangeticus genotypes. All the microelements, proximate, macro-elements, phytochemicals, PA profiles, and ARP of A. gangeticus under MSCS, and SSCS levels were much higher in comparison with the control. It can be utilized as preferential food for our daily diets as these antiradical compounds have strong antioxidants. Salt-treated A. gangeticus contributed to excellent quality in the end product in terms of microelements, proximate, macro-elements, phytochemicals, PA profiles, and ARP. A. gangeticus can be cultivated as an encouraging substitute crop in salt-affected areas of the world.

Comprehensive physiological, transcriptomic, and metabolomic analyses reveal the synergistic mechanism of Bacillus pumilus G5 combined with silicon alleviate oxidative stress in drought-stressed Glycyrrhiza uralensis Fisch

Glycyrrhiza uralensis Fisch. is often cultivated in arid, semi-arid, and salt-affected regions that suffer from drought stress, which leads to the accumulation of reactive oxygen species (ROS), thus causing oxidative stress. Plant growth-promoting bacteria (PGPB) and silicon (Si) have been widely reported to be beneficial in improving the tolerance of plants to drought stress by maintaining plant ROS homeostasis. Herein, combining physiological, transcriptomic, and metabolomic analyses, we investigated the response of the antioxidant system of G. uralensis seedlings under drought stress to Bacillus pumilus (G5) and/or Si treatment. The results showed that drought stress caused the overproduction of ROS, accompanied by the low efficiency of antioxidants [i.e., superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), the ascorbate (AsA)-glutathione (GSH) pool, total carotenoids, and total flavonoids]. Inversely, supplementation with G5 and/or Si enhanced the antioxidant defense system in drought-stressed G. uralensis seedlings, and the complex regulation of the combination of G5 and Si differed from that of G5 or Si alone. The combination of G5 and Si enhanced the antioxidant enzyme system, accelerated the AsA-GSH cycle, and triggered the carotenoid and flavonoid metabolism, which acted in combination via different pathways to eliminate the excess ROS induced by drought stress, thereby alleviating oxidative stress. These findings provide new insights into the comparative and synergistic roles of PGPB and Si in the antioxidant system of plants exposed to drought and a guide for the application of PGPB combined with Si to modulate the tolerance of plants to stress.

Diverse Physiological Roles of Flavonoids in Plant Environmental Stress Responses and Tolerance

Flavonoids are characterized as the low molecular weight polyphenolic compounds universally distributed in planta. They are a chemically varied group of secondary metabolites with a broad range of biological activity. The increasing amount of evidence has demonstrated the various physiological functions of flavonoids in stress response. In this paper, we provide a brief introduction to flavonoids' biochemistry and biosynthesis. Then, we review the recent findings on the alternation of flavonoid content under different stress conditions to come up with an overall picture of the mechanism of involvement of flavonoids in plants' response to various abiotic stresses. The participation of flavonoids in antioxidant systems, flavonoid-mediated response to different abiotic stresses, the involvement of flavonoids in stress signaling networks, and the physiological response of plants under stress conditions are discussed in this review. Moreover, molecular and genetic approaches to tailoring flavonoid biosynthesis and regulation under abiotic stress are addressed in this review.

Application of Potassium after Waterlogging Improves Quality and Productivity of Soybean Seeds

Potassium (K) improves the stress tolerance of crop plants, which varies on the timing of K application and crop varieties. Soybean is a promising crop that can easily fit with the cropping pattern during kharif I season, when water logging occurs due to sudden rain. Therefore, an experiment was conducted to determine the effect of K management on the productivity and seed quality of soybean under normal and waterlogged conditions. The treatments comprised three factors, namely soybean genotypes (BU Soybean-1 and BU Soybean-2), waterlogging (WL) (control and WL for 4 days at the flowering stage (FS)), and K application (full dose as basal and 50% as basal +50% as top dress after termination of the flooding). The trial was laid out in a randomized complete block design with three replications. Findings revealed that BU Soybean-1 produced a higher number of pods and seeds pod−1 under control conditions with basal application of K. On the other hand, BU Soybean-2 produced taller plants and heavier grain, improving grain and straw yield under WL conditions when K was top dressed. The varieties absorbed a higher amount of nitrogen, phosphorus, and potassium under control conditions compared to WL when K was top dressed. Similarly, the seed protein content of both varieties was higher in the control condition with a top dressing of K. However, a higher percentage of seed germination was obtained from BU Soybean-2 in the control condition with a top dressing of K. Further, more electrical conductivity and more mean germination time were recorded in the case of BU Soybean-2 under WL with the basal application of K. Split application of 50% of recommended K fertilizer after the recession of flood water could be suggested for improved grain yield in flood-affected soybean growing areas.

Foliar-applied selenium nanoparticles alleviate cadmium stress through changes in physio-biochemical status and essential oil profile of coriander (Coriandrum sativum L.) leaves

Since large areas of agricultural soils around the world are contaminated by Cd, a cost-effective and practical method is needed for the safe production of edible plants. The effective role of many nanomaterials to improve plant yield by mitigating environmental pollutions is addressed; however, the impacts of selenium nanoparticles (Se-NPs) have not been well-known yet. The aim of this work was to investigate foliar application of Se-NPs on yield, water content, proline concentration, phenolic content, lipid peroxidation, and essential oil (EO) attributes of coriander (Coriandrum sativum L.) under Cd stress. The plants were exposed to Cd contamination (0, 4, and 8 mg L-1) and foliar application of Se-NPs (0, 20, 40, and 60 mg L-1). The results showed increased Cd accumulation in roots and shoots of coriander plants upon Cd stress; however, Se-NPs alleviated the uptake of Cd. Cd toxicity, particularly 8 mg L-1, decreased shoot and root weight, chlorophyll (Chl), and relative water content (RWC), while Se-NPs improved these attributes. The Cd concentration at 4 mg L-1 and Se-NPs at 40 or 60 mg L-1 increased phenolic and flavonoid contents as well as EO yield. Proline concentration and malondialdehyde (MDA) increased by enhancing Cd stress, but Se-NPs decreased MDA. The GC/MS analysis showed that the main EO constitutes were n-decanal (18.80-29.70%), 2E-dodecanal (14.23-19.87%), 2E-decanal (12.60-19.40%), and n-nonane (7.23-12.87%), representing different amounts under Cd pollution and Se-NPs. To sum up, Se-NPs at 40-60 mg L-1 are effective in alleviating Cd stress.

How Do Plants Respond to Combined Drought and Salinity Stress?-A Systematic Review

Plants are frequently exposed to one or more abiotic stresses, including combined salinity-drought, which significantly lowers plant growth. Many studies have been conducted to evaluate the responses of plants to combined salinity and drought stress. However, a meta-analysis-based systematic review has not been conducted yet. Therefore, this study analyzed how plants respond differently to combined salinity-drought stress compared to either stress alone. We initially retrieved 536 publications from databases and selected 30 research articles following a rigorous screening. Data on plant growth-related, physiological, and biochemical parameters were collected from these selected articles and analyzed. Overall, the combined salinity-drought stress has a greater negative impact on plant growth, photosynthesis, ionic balance, and oxidative balance than either stress alone. In some cases, salinity had a greater impact than drought stress and vice versa. Drought stress inhibited photosynthesis more than salinity, whereas salinity caused ionic imbalance more than drought stress. Single salinity and drought reduced shoot biomass equally, but salinity reduced root biomass more than drought. Plants experienced more oxidative stress under combined stress conditions because antioxidant levels did not increase in response to combined salinity-drought stress compared to individual salinity or drought stress. This study provided a comparative understanding of plants' responses to individual and combined salinity and drought stress, and identified several research gaps. More comprehensive genetic and physiological studies are needed to understand the intricate interplay between salinity and drought in plants.

Exogenous menadione sodium bisulphite alleviates detrimental effects of alkaline stress on wheat (Triticum aestivum L.)

Menadione sodium bisulphite (MSB) is known to augment plant defense responses against abiotic and biotic stresses. Wheat is an essential cereal with significant sensitivity to alkaline stress. The present study investigated the effects of MSB seed priming (5 and 10 mM) in alleviating the damaging effects of alkaline stress on hydroponically grown wheat cultivars (salt-sensitive cv. MH-97 and salt-tolerant cv. Millat-2011). Our findings revealed a significant reduction in growth, chlorophyll contents, total soluble proteins, free amino acids, K+, Ca2+, P, and K+/Na+ in wheat cultivars under alkaline stress. In contrast, a noteworthy accretion in lipid peroxidation, H2O2 production, proline levels, antioxidant enzyme activities, soluble sugars, antioxidant compounds, and Na+ levels was noticed in wheat plants grown in alkaline hydroponic medium. MSB priming significantly lowered chlorophyll degradation, Na+ levels, and osmolyte accumulation. Further, K+/Na+ ratio, antioxidant compounds, and antioxidant enzyme activities were higher in plants primed with MSB. Therefore, seed priming eminently protected plants by regulating osmotic adjustment and strengthening oxidative defense under alkaline stress. Plants administered 5 mM MSB as seed priming manifested better tolerance to alkaline stress.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-022-01250-z.