Organic acids: versatile stress-response roles in plants

Comprehensive compositional analysis of liquid organic product prepared by industrialized hydrothermal cracking of biomass waste and its potential application as fertilizer

Hydrothermal cracking involves the conversion of organic waste into efficient fertilizer through hydrolysis at temperatures ranging from 180 to 220 °C and pressures of 1.5 to 2.45 MPa, which offers significant advantages in shortening the production cycle, enhancing efficiency, and decomposing antibiotics. As a result, it holds immense practical value for promoting organic fertilizer manufacturing processes globally. The products derived from hydrothermal cracking can be categorized into solid and liquid components. Extensive research has focused on the composition and use of solids, while studies on liquids have mainly examined basic characteristics. The study aimed to comprehensively analyze the components in liquid products prepared through hydrothermal cracking and evaluate their suitability as liquid fertilizers. Specifically, we employed rigorous analytical techniques to accurately identify and quantify medium and trace elements, organic acids, amino acids, and plant growth regulators. Furthermore, we carried out a planting experiment to assess the yield and soil changes following the application of liquid products in maize cultivation. The experimental data revealed that the liquid product contained abundant medium and trace elements, along with 6.22 g/L free amino acids and 9.22 g/L organic acids. It is noteworthy that this liquid product contained 1.22 × 105 pg/mL ABA, 6.26 × 103 pg/mL IAA, 1.07 × 102 pg/mL IBA, and 3.60 × 10-2 pg/mL GA3. The utilization of this liquid product has the potential to enhance the disease resistance of maize crops and promote the accumulation of nitrate nitrogen in the soil. By understanding the composition of liquid products via hydrothermal cracking, valuable insights can be gained into their potential benefits for agricultural and ecological applications.

Organic acids released by submerged macrophytes with damaged leaves alter the denitrification microbial community in rhizosphere

Submerged macrophytes have important impacts on the denitrification and anaerobic ammonia-oxidizing (anammox) processes. Leaf damage in these plants probably changes the rhizosphere environment, affecting organic acid release and denitrifying bacteria. However, there is a lack of comprehensive understanding of the specific changes. This study investigated these changes in the rhizosphere of Potamogeton crispus with four degrees of leaf excision. When 0 %, 30 %, 50 % and 70 % of leaves were excised, the concentrations of total organic acid were 31.45, 32.67, 38.26, and 35.16 mg/L, respectively. The abundances of nirS-type denitrifying bacteria were 2.10 × 1010, 1.59 × 1010, 2.54 × 1010, and 4.67 × 1010 copies/g dry sediment, respectively. The abundances of anammox bacteria were 7.58 × 109, 4.59 × 109, 3.81 × 109, and 3.90 × 109 copies/g dry sediment, respectively. The concentration of total organic acids and the abundance of two denitrification microorganisms in the rhizosphere zone were higher than those in the root zone and non-rhizosphere zone. With increasing leaf damage, the number of OTUs in the Pseudomonas genus of nirS-type denitrifying bacteria first increased and then decreased, while that of the Thauera genus was relatively stable. The overall increase in the OTU number of anammox bacteria indicated that leaf damage promotes root exudates release, thereby leading to an increase in their diversity. The co-occurrence network revealed that the two denitrification microorganisms had about 60.52 % positive connections in rhizosphere while 64.73 % negative connections in non-rhizosphere. The abundance and community composition of both denitrification microorganisms were positively correlated with the concentrations of various substances such as oxalic acid, succinic acid, total organic acids and NO2--N. These findings demonstrate that submerged plant damage has significantly impacts on the structure of denitrification microbial community in the rhizosphere, which may alter the nitrogen cycling process in the deposit sediment. SYNOPSIS: This study reveals leaf damage of macrophyte changed the rhizosphere denitrification microbial community, which is helpful to further understand the process of nitrogen cycle in water.

Exposure to toxic cadmium concentration induce physiological and molecular mechanisms alleviating herbivory infestation in Wedelia

Cadmium (Cd) toxicity induces significant disruptions in growth and development, plants have developed strategies to alleviate metal toxicity promoting establishment even during herbivores infestation. The study demonstrates that W. trilobata maintains growth and development under the combined stress of Cd exposure and herbivore invasion by Spodoptera litura, in contrast to W. chinensis. Cd toxicity markedly reduce shoot elongation and total fresh biomass, and a significant decrease in the dry weight of the shoot biomass and leaf count by 19%, 18%, 16%, and 19% in W. trilobata compared to controls. An even more pronounced decrease of 35%, 43%, 45% and 43% was found in W. chinensis. Compared to W. chinensis, W. trilobata showed a higher increase in phytohormone production including abscisic acid (ABA), gibberellic acid (GA3), indole-3-acetic acid (IAA) and methyl jasmonic acid (JA-me) under both Cd and herbivory stress as compared with respective controls. In addition, leaf ultra-structure also showed the highest damage to cell membranous structures by Cd-toxicity in W. chinensis. Furthermore, RNA-seq analysis revealed numerous genes viz., EMSY, MCCA, TIRI, BED-type, ABA, JAZ, CAB-6, CPSI, LHCII, CAX, HNM, ABC-Cd-trans and GBLP being differentially expressed between Cd-stress and herbivory groups in both W. trilobata and W. chinensis, with a particular emphasis on genes associated with metal transport and carbohydrate metabolism. Analyses employing the Gene Ontology (GO) system, the Clusters of Orthologous Groups (COG) categorization, and the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, highlight the functional and evolutionary relationships among the genes of the Phenylpropanoid and Flavonoid biosynthesis pathways and brassinosterod metabolism, associated with plant growth and development under Cd-toxicity and herbivory. W. trilobata opposite of W. chinensis, significantly improve plant growth and mitigates Cd toxicity through modulation of metabolic processes, and regulation of responsible genes, to sustain its growth under Cd and herbivory stress, which can be used in stress improvement in plants for sustainable ecosystem biodiversity and food security.

The Role of Low-Molecular-Weight Organic Acids in Metal Homeostasis in Plants

Low-molecular-weight organic acids (LMWOAs) are essential O-containing metal-binding ligands involved in maintaining metal homeostasis, various metabolic processes, and plant responses to biotic and abiotic stress. Malate, citrate, and oxalate play a crucial role in metal detoxification and transport throughout the plant. This review provides a comparative analysis of the accumulation of LMWOAs in excluders, which store metals mainly in roots, and hyperaccumulators, which accumulate metals mainly in shoots. Modern concepts of the mechanisms of LMWOA secretion by the roots of excluders and hyperaccumulators are summarized, and the formation of various metal complexes with LMWOAs in the vacuole and conducting tissues, playing an important role in the mechanisms of metal detoxification and transport, is discussed. Molecular mechanisms of transport of LMWOAs and their complexes with metals across cell membranes are reviewed. It is discussed whether different endogenous levels of LMWOAs in plants determine their metal tolerance. While playing an important role in maintaining metal homeostasis, LMWOAs apparently make a minor contribution to the mechanisms of metal hyperaccumulation, which is associated mainly with root exudates increasing metal bioavailability and enhanced xylem loading of LMWOAs. The studies of metal-binding compounds may also contribute to the development of approaches used in biofortification, phytoremediation, and phytomining.

Network analysis of metabolomics, transcriptome and hormones reveals propionic acid-mediated novel survival strategy against drought in wheat

Propionic acid (PA), a low-molecular-weight organic acid, is crucial to plant life metabolism. However, the regulatory mechanism of PA-mediated drought resistance in wheat remains largely unknown. Herein, we reported on a regulatory network of PA-mediated drought resistance in wheat using integrated transcriptome and metabolomics analysis and verified genes associated with drought resistance. Compared to the water-treated group, the application of PA alleviated the damage of drought by increasing plant water content, antioxidant enzyme activities and decreasing the malondialdehyde level (MDA). Transcriptome and metabolomics analysis revealed that PA triggered upregulation of key genes and metabolites, including TaBCAT, TaALDH6A1, TaALDH7A1, TaCHI, TaFLS, chrysin, and galangin, which were involved in valine, leucine and isoleucine degradation or flavonoid biosynthesis, respectively. In addition, the expression of genes encoding auxin-related transcription factors (TFs) strikingly increased, such as auxin/indoleacetic acid (AUX/IAA) and auxin response factor (ARF). Moreover, PA activated abscisic acid (ABA) and indole-3-acetic acid (IAA) signalling pathways. Taken together, our findings suggest that PA promotes energy metabolism and antioxidant activities to confer wheat drought resistance by introducing comprehensive and systemic effects of valine, leucine and isoleucine degradation flavonoid biosynthesis. Furthermore, activated AUX/IAA and ARF TFs might serve vital roles in drought resistance via modulating IAA signalling. This study provides novel insights into PA-mediated crop resistance and the improvement of the agroecological environment.

The response of root-zone soil bacterial community, metabolites, and soil properties of Sanyeqing medicinal plant varieties to anthracnose disease in reclaimed land, China

Objectives

To enhance the utilization of reclaimed land, Sanyeqing (SYQ) has been extensively cultivated in Zhejiang province, China. However, the prevalence of anthracnose has significantly hindered SYQ growth, emerging as a primary obstacle to its production. This study aimed to elucidate SYQ's responses to anthracnose in reclaimed land environments by comprehensively analyzing root-zone bacterial community structure, metabolites, and soil properties.

Methods

The experiment was conducted on reclaimed land in Chun'an, China. In order to evaluate the responses of SYQ to anthracnose, the fresh and dry weight of SYQ tubes, the soil properties, the high-throughput sequencing, and metabolomics assay were carried out.

Results

Significant differences were observed between an anthracnose-resistant variety (A201714) and an anthracnose-susceptibile variety (B201301). Fresh and dry weight increased 131.53 % and 144.82 % for A201714 compared to B201301.Lacibacterium (39.85 %), Gp6 (21.83 %), Gp5 (21.49 %), and Sphingomonas (18.84 %) were more prevalent, whereas Gp3 (22.71 %), WPS-1 (18.88 %), Gp4 (15.60 %), Subdivision3 (14.70 %), Chryseolinea (14.37 %), and Nitrospira (0.76 %) were less prevalent in A201714 than B201301. A total of 24 bacterial biomarkers were detected in all soil samples, while the network suggests a more stable soil bacterial community in A201714 than in B201301. Eight differentially expressed metabolites (DEMs) that belonged to lipids and lipid-like molecules, organic acids and derivatives, benzenoids, nucleosides, nucleotides, and analogues were found between two soil samples, and all these eight DEMs were downregulated in A201714 and had a strong correlation with 12 genera of bacteria. Moreover, the data from the redundancy analysis indicated that the main variables affecting changes in the bacterial communities were pH, available phosphorus (AP), available potassium (AK), microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN).

Conclusion

This research offers new insights into the SYQ response to anthracnose in reclaimed land and provides valuable recommendations for the high-quality SYQ cultivation and production.

Effect of Different Seasons and Development Stages on the Chemical Composition and Bioactive Potential of Cardoon

Cynara cardunculus L. (cardoon) is a wild species of the Mediterranean basin and is highly appreciated due to its rich nutritional value and versatile industrial applications. It is widely known that environmental conditions, such as air temperature, humidity, and solar radiation, among others, play a crucial role in plant phenological variations and the chemical composition and bioactive properties of different plant tissues of cardoon. This study applied several statistical methods to uncover the variations in biomolecules of different cardoon tissues collected in Greece over the growth cycle. The influence of the different seasons on the species is evident, resulting in a clear discrimination between the samples harvested throughout the growth cycle. In addition, the observed fluctuations in chemical composition are consistent with each vegetable tissue's functions and the plant's different physiological processes. This work allows for a better understanding and knowledge of the species, encouraging more profitable and sustainable use of all the plant parts.

Tolerance enhancement of Dendrobium officinale by salicylic acid family-related metabolic pathways under unfavorable temperature

BACKGROUND

Unfavorable temperatures significantly constrain the quality formation of Dendrobium officinale, severely limiting its food demand. Salicylic acid (SA) enhances the resistance of D. officinale to stress and possesses various analogs. The impact and mechanism of the SA family on improving the quality of D. officinale under adverse temperature conditions remains unclear.

RESULTS

Combined with molecular docking analysis, chlorophyll fluorescence and metabolic analysis after treatments with SA analogues or extreme temperatures are performed in this study. The results demonstrate that both heat and cold treatments impede several main parameters of chlorophyll fluorescence of D. officinale, including the ΦPSII parameter, a sensitive growth indicator. However, this inhibition is mitigated by SA or its chemically similar compounds. Comprehensive branch imaging of ΦPSII values revealed position-dependent improvement of tolerance. Molecular docking analysis using a crystal structure model of NPR4 protein reveals that the therapeutic effects of SA analogs are determined by their binding energy and the contact of certain residues. Metabolome analysis identifies 17 compounds are considered participating in the temperature-related SA signaling pathway. Moreover, several natural SA analogs such as 2-hydroxycinnamic acid, benzamide, 2-(formylamino) benzoic acid and 3-o-methylgallic acid, are further found to have high binding ability to NPR4 protein and probably enhance the tolerance of D. officinale against unfavorable temperatures through flavone and guanosine monophosphate degradation pathways.

CONCLUSIONS

These results reveal that the SA family with a high binding capability of NPR4 could improve the tolerance of D. officinale upon extreme temperature challenges. This study also highlights the collaborative role of SA-related natural compounds present in D. officinale in the mechanism of temperature resistance and offers a potential way to develop protective agents for the cultivation of D. officinale.

Polygonum ciliinerve (Nakai) Ohwi: a review of its botany, traditional uses, phytochemistry, pharmacology, pharmacokinetics and toxicology

Polygonum ciliinerve (Nakai) Ohwi is a perennial twining vine plant from the Polygonaceae family, which is a Chinese herbal medicine with great value for development and utilization. The purpose of this paper is to provide a systematic review of the botany, traditional uses, phytochemistry, pharmacology, pharmacokinetics, and toxicology of Polygonum ciliinerve (Nakai) Ohwi, as well as an outlook on the future research directions and development prospects of the plant. Data on Polygonum ciliinerve (Nakai) Ohwi were obtained from different databases, including China National Knowledge Infrastructure, Baidu Academic, Wanfang Database, Google Academic, PubMed, Web of Science, SpringerLink, Wiley; books; standards; and Ph.D. and MSc theses. So far, 86 compounds have been identified from Polygonum ciliinerve (Nakai) Ohwi, including anthraquinones, stilbenes, flavonoids, tannins, chromogenic ketones, organic acids and esters, lignans, isobenzofurans, alkaloids, naphthols, and others. Studies have found that Polygonum ciliinerve (Nakai) Ohwi has a wide range of pharmacological effects, including antiviral, antibacterial, anti-inflammatory and analgesic, antitumor, immunomodulatory, hypoglycemic, and antioxidant effects. Clinically, Polygonum ciliinerve (Nakai) Ohwi is very effective in the treatment of gastritis and chronic gastritis. Based on its traditional use, chemical composition, and pharmacological activity, Polygonum ciliinerve (Nakai) Ohwi is a promising source of natural medicine in drug development.

Bioactive Compound Profiling and Antioxidant Activity of Phytelephas tenuicaulis and Other Amazonian Fruits

The Amazon region is home to many plant species, many of which have not been studied. The objective was to evaluate the physicochemical properties, bioactive compounds, and antioxidant activity of Phytelephas tenuicalis (tintiuk), Grias neuberthii (apai), Euterpe oleracea (acai), and Mauritia flexuosa (brown moriche). Physicochemical analyses were carried out on fresh fruit from local markets. Bioactive compounds (carotenoids, phenolics, vitamin C, and organic acids) were quantified in the freeze-dried pulp by rapid-resolution liquid chromatography (RRLC), and antioxidant activity was determined by ABTS and DPPH assays. The results showed high soluble solids (10.7 °Brix) and ascorbic acid (67.3 mg/100 g DW) in tintiuk; β-carotene (63.4 mg/100 g DW) and malic acid (19.6 g/100 g DW) in brown moriche; quercetin (944.2 mg/100 g DW) and antioxidant activity by ABTS (6.7 mmol ET/100 g DW) in apai; and citric acid (2.1 g/100 g DW) in acai. These results indicate interesting bioactive properties that could increase the consumption of these fruits nationally and internationally, benefiting local farmers and stimulating the development of new products in functional food, medicine, and cosmetics.

Unravelling the halophyte Suaeda maritima as an efficient candidate for phytostabilization of cadmium and lead: Implications from physiological, ionomic, and metabolomic responses

Cadmium (Cd) and lead (Pb) are among the most toxic heavy metals affecting human health and crop yield. Suaeda maritima (L.) Dumort is an obligate halophyte that is well adapted to saline soil. The inbuilt salinity tolerance mechanisms of halophytes help them to survive in heavy metal-contaminated rhizospheric soil. In the present study, growth and ionomic responses, reactive oxygen species (ROS) accumulation, modulations of phytochelatins, antioxidative defense, and metabolomic responses were studied in S. maritima imposed to Cd and Pb stresses with an aim to elucidate Cd and Pb tolerance mechanisms and phytoremediation potential of this halophyte. Our results showed a reduction of biomass in S. maritima, which may serve as an energy conservation strategy for survival under heavy metal stress. The increased accumulation of ROS with concomitant higher expression of various antioxidative enzymes suggests the efficient scavenging of ROS. The metabolite profiling revealed significant up-regulation of sugars, sugar alcohols, amino acids, polyphenols, and organic acids under Cd and Pb stresses suggesting their possible role in osmotic balance, ionic homeostasis, ROS scavenging, and signal transduction for stress tolerance. In S. maritima, the translocation factors (Tf) are <1 in both Cd and Pb treatments, which indicates that this halophyte has high phytostabilization potential for Cd and Pb in roots and through restricted translocation of heavy metal ions to the aboveground part. The findings of this study offer comprehensive information on Cd and Pb tolerance mechanisms in S. maritima and suggest that this halophyte can detoxify the HMs through physiological, ionic, antioxidative, and metabolic regulations.

The Phosphorus-Iron Nexus: Decoding the Nutrients Interaction in Soil and Plant

Phosphorus (P) and iron (Fe) are two essential mineral nutrients in plant growth. It is widely observed that interactions of P and Fe could influence their availability in soils and affect their homeostasis in plants, which has received significant attention in recent years. This review presents a summary of latest advances in the activation of insoluble Fe-P complexes by soil properties, microorganisms, and plants. Furthermore, we elucidate the physiological and molecular mechanisms underlying how plants adapt to Fe-P interactions. This review also discusses the current limitations and presents potential avenues for promoting sustainable agriculture through the optimization of P and Fe utilization efficiency in crops.

Redesigning a S-nitrosylated pyruvate-dependent GABA transaminase 1 to generate high-malate and saline-alkali-tolerant tomato

Although saline-alkali stress can improve tomato quality, the detailed molecular processes that balance stress tolerance and quality are not well-understood. Our research links nitric oxide (NO) and γ-aminobutyric acid (GABA) with the control of root malate exudation and fruit malate storage, mediated by aluminium-activated malate transporter 9/14 (SlALMT9/14). By modifying a specific S-nitrosylated site on pyruvate-dependent GABA transaminase 1 (SlGABA-TP1), we have found a way to enhance both plant's saline-alkali tolerance and fruit quality. Under saline-alkali stress, NO levels vary in tomato roots and fruits. High NO in roots leads to S-nitrosylation of SlGABA-TP1/2/3 at Cys316/258/316, reducing their activity and increasing GABA. This GABA then reduces malate exudation from roots and affects saline-alkali tolerance by interacting with SlALMT14. In fruits, a moderate NO level boosts SlGABA-TP1 expression and GABA breakdown, easing GABA's block on SlALMT9 and increasing malate storage. Mutants of SlGABA-TP1C316S that do not undergo S-nitrosylation maintain high activity, supporting malate movement in both roots and fruits under stress. This study suggests targeting SlGABA-TP1Cys316 in tomato breeding could significantly improve plant's saline-alkali tolerance and fruit quality, offering a promising strategy for agricultural development.

Chickpea (Cicer arietinum) PHO1 family members function redundantly in Pi transport and root nodulation

Phosphorus (P), a macronutrient, plays key roles in plant growth, development, and yield. Phosphate (Pi) transporters (PHTs) and PHOSPHATE1 (PHO1) are central to Pi acquisition and distribution. Potentially, PHO1 is also involved in signal transduction under low P. The current study was designed to identify and functionally characterize the PHO1 gene family in chickpea (CaPHO1s). Five CaPHO1 genes were identified through a comprehensive genome-wide search. Phylogenetically, CaPHO1s formed two clades, and protein sequence analyses confirmed the presence of conserved domains. CaPHO1s are expressed in different plant organs including root nodules and are induced by Pi-limiting conditions. Functional complementation of atpho1 mutant with three CaPHO1 members, CaPHO1, CaPHO1;like, and CaPHO1;H1, independently demonstrated their role in root to shoot Pi transport, and their redundant functions. To further validate this, we raised independent RNA-interference (RNAi) lines of CaPHO1, CaPHO1;like, and CaPHO1;H1 along with triple mutant line in chickpea. While single gene RNAi lines behaved just like WT, triple knock-down RNAi lines (capho1/like/h1) showed reduced shoot growth and shoot Pi content. Lastly, we showed that CaPHO1s are involved in root nodule development and Pi content. Our findings suggest that CaPHO1 members function redundantly in root to shoot Pi export and root nodule development in chickpea.

Morpho-physiological adaptations to weed competition impair green bean (Phaseolus vulgaris) ability to overcome moderate salt stress

The two stresses of weed competition and salt salinity lead to crop yield losses and decline in the productivity of agricultural land. These constraints threaten the future of food production because weeds are more salt stress tolerant than most crops. Climate change will lead to an increase of soil salinity worldwide, and possibly exacerbate the competition between weeds and crops. This aspect has been scarcely investigated in the context of weed-crop competition. Therefore, we conducted a field experiment on green beans (Phaseolus vulgaris ) to investigate the combined impact of weed competition and salt stress on key morpho-physiological traits, and crop yield. We demonstrated that soil salinity shifted weed composition toward salt tolerant weed species (Portulaca oleracea and Cynodon dactylon ), while it reduced the presence of lower tolerance species. Weed competition activated adaptation responses in green bean such as reduced leaf mass per area and biomass allocation to the stem, unchanged stomatal density and instantaneous water use efficiency, which diverge from those that are typically observed as a consequence of salt stress. The morpho-physiological modifications caused by weeds is attributed to the alterations of light intensity and/or quality, further confirming the pivotal role of the light in crop response to weeds. We concluded that higher yield loss caused by combined salt stress and weed competition is due to impaired morpho-physiological responses, which highlights the negative interaction between salt stress and weed competition. This phenomenon will likely be more frequent in the future, and potentially reduce the efficacy of current weed control methods.

Botany, traditional usages, phytochemistry, pharmacology, and toxicology of Guilandina bonduc L.: a systematic review

Guilandina bonduc L. is popularly known as a fever nut that grows widely in evergreen forests and moist deciduous forests with a pantropical distribution. The plant is highly therapeutic in various systems of medicine, including Ayurveda, Siddha, and homeopathy. The purpose of this review is to analyze the published data on G. bonduc, including traditional uses, taxonomic position, botanical description, phytochemistry, pharmacological properties, and toxicological assessment of its various parts. Phytochemical and pharmacological studies were the main focus of this review. The previously published research on G. bonduc was tracked from scientific databases such as Online Library, Google, Taylor and Francis, PubMed, Research Gate, Scopus, Springer, Wiley, Web of Sciences. Numerous phytochemical, pharmaceutical, and pharmacological studies have been carried out on the various parts of G. bonduc. To date, more than 97 phytochemicals have been isolated from the leaves, roots, stems, stem bark, flowers, twigs, and seeds of this plant. The phytochemicals isolated from the plants are flavonoids, homoisoflavonoids, terpenoids, diterpenoids, steroids, fatty acids, alkanes, acids, phenols, ketones, esters, amides, azides, silanes, and ether groups. This plant has been extensively studied in in vitro and in vivo pharmacological experiments, where it showed analgesic, anti-inflammatory, antioxidant, antiviral, antidiabetic, abortive, anticataleptic, immunomodulatory, and antiestrogenic effects. This comprehensive review revealed that phytochemicals isolated from various parts of G. bonduc have significant therapeutic efficacy, with promising anticancer, antidiabetic, hepatoprotective, antioxidant, and antimicrobial activities. This review provides a good source of information for the development of a drug using modern scientific tools, in view of its underexplored traditional uses. Further studies on preclinical and clinical trials and toxicological studies on the bioactive molecules of G. bonduc to validate its traditional uses are warranted.

Nanoplastics increase algal absorption and toxicity of Cd through alterations in cell wall structure and composition

Nanoplastics (NPs) may act as carriers of heavy metals and cause complex toxicity to aquatic organisms, while the exact role of NPs in the joint toxicity remains unclear. Here, we investigated the joint toxicity of polystyrene NPs (PS-NPs) and Cd to freshwater algae (Chlorella vulgaris). It was found that PS-NPs (1 mg L-1) could hardly enter algal cells and slightly inhibit algal growth (p < 0.01). The effect of PS-NPs as carriers on the joint toxicity of PS-NPs and heavy metals could be neglected because of the limited adsorption of Cd by PS-NPs, while the PS-NPs altered the cell wall structure and composition, which resulted in the increased algal absorption and toxicity of Cd. Compared to the low dose Cd (0.4 mg L-1) treatment alone, the extracellular and intracellular Cd contents in the cotreatment were significantly increased by 27.3 % and 18.0 %, respectively, due to the increased contents of cell wall polysaccharides (pectin and hemicellulose in particular) by the PS-NPs. Furthermore, after the high dose Cd (2 mg L-1) exposure, the inhibited polysaccharide biosynthesis and the loosen cell wall structure weakened the tolerance of cell wall to abiotic stress, facilitating the entry of PS-NPs into the algal cells and inducing the higher toxicity. These results elucidate the mechanism by which NPs enhance heavy metal toxicity to algae, providing a novel insight into environmental risks of NPs.

Metabolite profiling and histochemical localization of alkaloids in Hippeastrum papilio (Ravena) van Scheepen

Hippeastrum papilio (Amaryllidaceae) is a promising new source of galanthamine - an alkaloid used for the cognitive treatment of Alzheimer's disease. The biosynthesis and accumulation of alkaloids are tissue - and organ-specific. In the present study, histochemical localization of alkaloids in H. papilio's plant organs with Dragendorff's reagent, revealed their presence in all studied samples. Alkaloids were observed in vascular bundles, vacuoles, and intracellular spaces, while in other plant tissues and structures depended on the plant organ. The leaf parenchyma and the vascular bundles were indicated as alkaloid-rich structures which together with the high proportion of alkaloids in the phloem sap (49.3% of the Total Ion Current - TIC, measured by GC-MS) indicates the green tissues as a possible site of galanthamine biosynthesis. The bulbs and roots showed higher alkaloid content compared to the leaf parts. The highest alkaloid content was found in the inner bulb part. GC-MS metabolite profiling of H. papilio's root, bulb, and leaves revealed about 82 metabolites (>0.01% of TIC) in the apolar, polar, and phenolic acid fractions, including organic acids, fatty acids, sterols, sugars, amino acids, free phenolic acids, and conjugated phenolic acids. The most of organic and fatty acids were in the peak part of the root, while the outermost leaf was enriched with sterols. The outer and middle parts of the bulb had the highest amount of saccharides, while the peak part of the middle leaf had most of the amino acids, free and conjugated phenolic acids.

Urea reduces the sustainability of soil Cd immobilization by upregulating the expression of AmSTOP1 and AmMATE genes in edible amaranth roots

After cadmium (Cd) immobilization remediation in contaminated farmland soil, which forms of nitrogen fertilizer should be implemented to keep its sustainability? Urea and nitrate were used to compare for their effects on the remobilization of stabilized Cd in the rhizosphere soil of edible amaranth at nitrogen concentrations of 60, 95, and 130 mg kg-1. The results showed that compared to nitrate nitrogen, the Cd content in shoots increased by 76.2%, 65.6%, and 148% after applying three different concentrations of urea, and the total remobilization amount of Cd also increased by 16.0%, 24.9%, and 14.0% respectively. Urea application promotes root secretion of citric acid, malic acid, pyruvate, and γ-aminobutyric acid, crucial in remobilizing stable Cd. The application of urea promoted the expression of genes involved in sucrose transport, glycolysis, the TCA cycle, amino acid secretion, citric acid efflux, and proton efflux. Arabidopsis heterologous expression and yeast one-hybrid assays identify critical roles of AmMATE42 and AmMATE43 in citric acid and fumaric acid efflux, with AmSTOP1 activating their transcription. Inhibition of SIZ1 expression in urea treatment reduce AmSTOP1 SUMOylation, leading to increased expression of AmMATE42 and AmMATE43 and enhanced organic acids efflux. Using edible amaranth as a model vegetable, we discovered that urea is not beneficial to preserving the sustainability of stabilized Cd during the reuse of remediated farmlands contaminated with Cd.

Sewage sludge-derived nutrients and biostimulants stimulate rice leaf photosynthesis and root metabolism to enhance carbohydrate, nitrogen and antioxidants accumulation

The production of high quality liquid nitrogen fertilizer with both nutrient comprehensive and biostimulant properties by alkaline thermal hydrolysis of sewage sludge has shown great potential in agricultural production. However, little is known about the effects of sewage sludge-derived nutrients, and biostimulants (SS-NB) on leaf photosynthesis and root growth in rice. Phenotypic, metabolic and microbial analyses were used to reveal the mechanism of SS-NB on rice. Compared to NF treatment, phenotypic parameters (fresh/dry weight, soluble sugar, amino acid, protein) were increased by SS-NB in rice. SS-NB can enhance the photosynthesis of rice leaves by improving the photoconversion efficiency, chlorophyll content, ATP synthase activity, Rubisco and NADPH production. Meanwhile, SS-NB also increased antioxidant capacity (SOD, POD, CAT and proline) in rice leaf and root tissues. Metabolomics revealed that SS-NB application increased the expression levels of metabolites in root and leaf tissues, including carbohydrate, nitrogen and sulfur metabolism, amino acid metabolism, antioxidants, and phytohormone. Most importantly, the regulation of metabolites in rice root tissues is more sensitive than in leaf tissues, especially to the higher levels of antioxidants and phytohormones (IAA and GA) in rice root tissues. Furthermore, SS-NB increased the abundance of photosynthetic autotrophic, organic acids-degrading and denitrifying functional bacteria in rice roots and recruited plant growth-promoting bacteria (Azospirillum and norank_f_JG30-KF-CM45), while the NF treatment group resulted in an imbalance of the microbial community, leading to the dominance of pathogenic bacteria. The results showed that SS-NB had great application potential in crop growth and stress resistance improvement.

The PGPR Bacillus aryabhattai promotes soybean growth via nutrient and chlorophyll maintenance and the production of butanoic acid

Plant growth-promoting rhizobacteria (PGPR) colonize plant roots, establish a mutualistic relationship with the plants and help them grow better. This study reports novel findings on the plant growth-promoting effects of the PGPR Bacillus aryabhattai. Soil was collected from a soybean field, PGPR were isolated, identified, and characterized for their ability to promote plant growth and development. The bacterium was isolated from the soybean rhizosphere and identified as B. aryabhattai strain SRB02 via 16s rRNA sequencing. As shown by SEM, the bacterium successfully colonized rice and soybean roots within 2 days and significantly promoted the growth of the GA-deficient rice cultivar Waito-C within 10 days, as well as the growth of soybean plants with at least six times longer shoots, roots, higher chlorophyll content, fresh, and dry weight after 10 days of inoculation. ICP analysis showed up to a 100% increase in the quantity of 18 different amino acids in the SRB02-treated soybean plants. Furthermore, the 2-DE gel assay indicated the presence of several differentially expressed proteins in soybean leaves after 24 hrs of SRB02 application. MALDI-TOF-MS identified β-conglycinin and glycinin along with several other proteins that were traced back to their respective genes. Analysis of bacterial culture filtrates via GCMS recorded significantly higher quantities of butanoic acid which was approximately 42% of all the metabolites found in the filtrates. The application of 100 ppm butanoic acid had significantly positive effects on plant growth via chlorophyll maintenance. These results establish the suitability of B. aryabhattai as a promising PGPR for field application in various crops.

Bio-stimulants from medicinally and nutritionally significant plant extracts mitigate drought adversities in Zea mays through enhanced physiological, biochemical, and antioxidant activities

Drought stress poses a substantial threat to global plant productivity amid increasing population and rising agricultural demand. To overcome this problem, the utilization of organic plant growth ingredients aligns with the emphasis on eco-friendly farming practices. Therefore, the present study aimed to assess the influence of 30 botanical extracts on seed germination, seedling vigor, and subsequent maize plant growth under normal and water deficit conditions. Specifically, eight extracts showed significant enhancement in agronomical parameters (ranging from ∼2 % to ∼ 183 %) and photosynthetic pigments (ranging from ∼21 % to ∼ 195 %) of seedlings under drought conditions. Extended tests on maize in a greenhouse setting confirmed that the application of six extracts viz Moringa oleifera leaf (MLE), bark (MBE), Terminalia arjuna leaf (ALE), bark (ABE), Aegel marmelos leaf (BLE), and Phyllanthus niruri leaf (AmLE) improved plant growth and drought tolerance, as evident in improved physio-biochemical parameters. GC-MS analysis of the selected extracts unveiled a total of 51 bioactive compounds, including sugars, sugar alcohols, organic acids, and amino acids, and might be playing pivotal roles in plant acclimatization to drought stress. In conclusion, MLE, MBE, BLE, and ABE extracts exhibit significant potential for enhancing seedling establishment and growth in maize under both normal and water deficit conditions.

Effects of cattle manure compost application on crop growth and soil-to-crop transfer of cesium in a physically radionuclide-decontaminated field

Resuming crop production in physically decontaminated fields affected by radiocesium (134Cs and 137Cs) releases is crucial for restoring impacted areas. However, surface soil excavation to reduce radiocesium may lead to lower crop yield due to the loss of fertile topsoil. This study aimed to assess the effects of cattle manure compost (CMC) application on soil properties, crop growth, and 137Cs soil-to-crop transfer in a physically decontaminated field and pot experiment. Field trials were conducted during 2018-2022, with CMC (1 and 2 kg m-2 year-1) applied alongside conventional fertilization (CMC1 and CMC2 plots, respectively) in 2018-2019 and conventional fertilization alone in 2020-2022. Additionally, a pot experiment was used to evaluate the impact of CMC application in soil (1 kg m-2 year-1 for 5 years) on 137Cs transfer. In the field trial during 2018-2019, CMC1 and CMC2 plots exhibited higher soybean shoot dry weight (DW) compared with plots receiving conventional fertilization and additional K fertilizer (+K2O). CMC application also improved soil nutrient content. The transfer factor of 137Cs (TF-137Cs: plant 137Cs activity concentration/soil 137Cs activity concentration) followed the order CMC2 < CMC1 ≈ +K2O < conventional fertilization only (CF) and was negatively correlated with soil exchangeable K (Ex-K). During 2020-2022, when all plots received conventional fertilization alone, grain yields were higher in CMC1 and CMC2 plots than in the +K2O plot, with the lowest TF-137Cs in CMC2 plot followed by CMC1, +K2O, and CF plots. The pot experiment confirmed that CMC soil had a lower TF-137Cs and higher plant DW compared with CF soil with the same Ex-K level. Additionally, the soil exchangeable 137Cs (Ex-137Cs) level was significantly lower in CMC soil than CF soil. These findings demonstrate the potential of CMC application to improve crop growth and reduce 137Cs transfer in physically decontaminated fields.

Exploring the Phytochemical Composition and Biological Potential of Balkan Endemic Species Stachys scardica Griseb

Stachys scardica Griseb. is a Balkan endemic species listed in The Red Data Book of Bulgaria with the conservation status "endangered". Successful micropropagation was achieved on MS medium supplemented with 1.5 mg/L benzyladenine (BA), followed by a subsequent ex vitro adaptation in an experimental field resulting in 92% regenerated plants. Using nuclear magnetic resonance (NMR), phenylethanoid glycosides (verbascoside, leucosceptoside A), phenolic acids (chlorogenic acid), iridoids (allobetonicoside and 8-OAc-harpagide), and alkaloids (trigonelline) were identified, characteristic of plants belonging to the genus Stachys. High antioxidant and radical scavenging activities were observed in both in situ and ex vitro acclimated S. scardica plants, correlating with the reported high concentrations of total phenols and flavonoids in these variants. Ex vitro adapted plants also exhibited a well-defined anti-inflammatory potential, demonstrating high inhibitory activity against the complement system. Employing a disk diffusion method, a 100% inhibition effect was achieved compared to positive antibiotic controls against Staphylococcus epidermidis and Propionibacterium acnes, with moderate activity against Bacillus cereus. The induced in vitro and ex vitro model systems can enable the conservation of S. scardica in nature and offer future opportunities for the targeted biosynthesis of valuable secondary metabolites, with potential applications in the pharmaceutical and cosmetic industries.

A citrate efflux transporter important for manganese distribution and phosphorus uptake in rice

The plant citrate transporters, functional in mineral nutrient uptake and homeostasis, usually belong to the multidrug and toxic compound extrusion transporter family. We identified and functionally characterized a rice (Oryza sativa) citrate transporter, OsCT1, which differs from known plant citrate transporters and is structurally close to rice silicon transporters. Domain analysis depicted that OsCT1 carries a bacterial citrate-metal transporter domain, CitMHS. OsCT1 showed citrate efflux activity when expressed in Xenopus laevis oocytes and is localized to the cell plasma membrane. It is highly expressed in the shoot and reproductive tissues of rice, and its promoter activity was visible in cells surrounding the vasculature. The OsCT1 knockout (KO) lines showed a reduced citrate content in the shoots and the root exudates, whereas overexpression (OE) line showed higher citrate exudation from their roots. Further, the KO and OE lines showed variations in the manganese (Mn) distribution leading to changes in their agronomical traits. Under deficient conditions (Mn-sufficient conditions followed by 8 days of 0 μm MnCl2  · 4H2 O treatment), the supply of manganese towards the newer leaf was found to be obstructed in the KO line. There were no significant differences in phosphorus (P) distribution; however, P uptake was reduced in the KO and increased in OE lines at the vegetative stage. Further, experiments in Xenopus oocytes revealed that OsCT1 could efflux citrate with Mn. In this way, we provide insights into a mechanism of citrate-metal transport in plants and its role in mineral homeostasis, which remains conserved with their bacterial counterparts.

Under flooding conditions, controlled-release fertiliser coated microplastics affect the growth and accumulation of cadmium in rice by increasing the fluidity of cadmium and interfering with metabolic pathways

The combined pollution of microplastics (MPs) and Cd can affect plant growth and development and Cd accumulation, with most studies focusing on dryland soil. However, the effects of polyurethane (PU) controlled-release fertiliser coated MPs (PU MPs), which widely exist in rice systems, coupled with Cd on plant growth and Cd accumulation under flooding conditions are still unknown. Therefore, in the present study, in situ techniques were used to systematically study the effects of PU MPs and Cd coupling on the physiological and biochemical performance, metabolomics characteristics, rhizosphere bacterial community, and Cd bioavailability of rice in different soil types (red soil/cinnamon soil). The results showed that the effects of PU MPs on rice growth and Cd accumulation were concentration-dependent, especially in red soil. High PU concentration (1 %) inhibited rice root growth significantly (44 %). The addition of PU MPs inhibited photosynthetically active radiation, net photosynthesis, and transpiration rate of rice, mainly with low concentration (0.1 %) in red soil and high concentration (1 %) in cinnamon soil. PU MPs can enhance the expression of Cd resistance genes (cadC and copA) in soil, enhance the mobility of Cd, and affect the metabolic pathways of metabolites in the rhizosphere soil (red soil: fatty acid metabolism; cinnamon soil: amino acid degradation, heterobiodegradation, and nucleotide metabolism) to promote Cd absorption in rice. Especially in red soil, Cd accumulation in the root and aboveground parts of rice after the addition of high concentration PU (1 %) was 1.7 times and 1.3 times, respectively, that of the control (p < 0.05). Simultaneously, microorganisms can affect rice growth and Cd bioavailability by affecting functional bacteria related to carbon, iron, sulfur, and manganese. The results of the present study provide novel insights into the potential effects of PU MPs coupled with Cd on plants, rhizosphere bacterial communities, and Cd bioavailability.

Dynamics of organic acid exudation and rhizobacteria in maize rhizosphere respond to N-CDs

To sustainably feed the growing global population, it is essential to increase crop yields on limited land while reducing the use of fertilizers and agrochemicals. The rhizosphere regulation shows significant potential to address this challenge. Here, foliar applied doping of nitrogen in carbon dots (N-CDs) entered maize leaves, and were transported to the stems and roots. The internalized N-CDs significantly increased the biomass (26.4-93.8%) and photosynthesis (17.0-20.3 %) of maize seedling during the three-week application of N-CDs, providing the substrate for tricarboxylic acid cycle (TCA) in shoots and roots. Correspondingly, more organic acids involved in TCA cycle, such as citric acid (14.0-fold), succinic acid (4.4-fold) and malic acid (3.4-fold), were synthesized and then secreted into rhizosphere after exposed to N-CDs for one day. As the exposure time increased, greater secretion of above organic acids by the roots was induced. However, no significant change was observed in the relative abundance of rhizobacteria after foliar application with N-CDs for one day. After one week, the relative abundances of Azotobacter, Bacillus, Lysobacter, Mucilaginibacter, and Sphingomonas increased by 0.8-3.8 folds. The relative abundance of more beneficial rhizobacteria (Sphingomonas, Lysobacter, Rhizobium, Azotobacter, Pseudomonas, Mucilaginibacter and Bacillus) enriched by 0.3-6.0 folds after two weeks, and Sphingomonas, Flavisolibacter and Bacillus improved by 0.6-3.2 folds after three weeks. These dynamic changes suggested that N-CDs initiate the synthesis and secretion of organic acids and then recruited beneficial rhizobacteria. The hierarchical partitioning analysis further indicated that N-CDs-induced secretion of organic acids from the roots was the main drivers of rhizobacteria community dynamics. The differential microbes altered by N-CDs were mainly involved in nitrogen (N) and phosphorus (P) cycles, which are beneficial for N and P uptake, and maize growth. These results provide insights into understanding the rhizosphere regulation of nanomaterials to improve plant productivity and nutrient-use efficiency.

Functional analysis of ZmG6PE reveals its role in responses to low-phosphorus stress and regulation of grain yield in maize

A previous metabolomic and genome-wide association analysis of maize screened a glucose-6-phosphate 1-epimerase (ZmG6PE) gene, which responds to low-phosphorus (LP) stress and regulates yield in maize's recombinant inbred lines (RILs). However, the relationship of ZmG6PE with phosphorus and yield remained elusive. This study aimed to elucidate the underlying response mechanism of the ZmG6PE gene to LP stress and its consequential impact on maize yield. The analysis indicated that ZmG6PE required the Aldose_epim conserved domain to maintain enzyme activity and localized in the nucleus and cell membrane. The zmg6pe mutants showed decreased biomass and sugar contents but had increased starch content in leaves under LP stress conditions. Combined transcriptome and metabolome analysis showed that LP stress activated plant immune regulation in response to the LP stress through carbon metabolism, amino acid metabolism, and fatty acid metabolism. Notably, LP stress significantly reduced the synthesis of glucose-1-phosphate, mannose-6-phosphate, and β-alanine-related metabolites and changed the expression of related genes. ZmG6PE regulates LP stress by mediating the expression of ZmSPX6 and ZmPHT1.13. Overall, this study revealed that ZmG6PE affected the number of grains per ear, ear thickness, and ear weight under LP stress, indicating that ZmG6PE participates in the phosphate signaling pathway and affects maize yield-related traits through balancing carbohydrates homeostasis.

Rhizosphere environmental factors regulated the cadmium adsorption by vermicompost: Influence of pH and low-molecular-weight organic acids

Vermicompost is a promising amendment for immobilization of cadmium (Cd) in soils; however, its effectiveness can be influenced by rhizosphere environment conditions, such as pH and the presence of low-molecular-weight organic acids (LMWOAs). In this study, a batch experiment was conducted to examine the characteristics of Cd adsorption by vermicompost at different pH (pH = 3, 5, and 7) and after the addition of different LMWOAs (oxalic acid; citric acid; malic acid). Furthermore, a series of morphology and structural analyses were conducted to elucidate the mechanisms of observed effects. The results showed that the adsorption capacity of vermicompost for Cd increased as pH increased, and chemisorption dominated the adsorption process. Changes in pH altered adsorption performance by affecting the -OH groups of alcohol/phenol and the -CH2 groups of aliphatics. Further, the addition of oxalic acid promoted Cd adsorption, and the effect was concentration dependent. Modifying the verimicompost surface with more adsorption sites might be the main reason. Conversely, citric acid and malic acid showed the ability to inhibit Cd adsorption by vermicompost. Citric acid caused a blocking effect by covering flocculent substances on the vermicompost surface while reducing surface adsorption sites by dissolving mineral components such as iron oxides. However, the action of malic acid did not appear to be related to changes in morphology or the structure of vermicompost. Overall, the results of this study partially explain the limited effectiveness of Cd immobilization within the rhizosphere by vermicompost, and provide theoretical support for regulating rhizosphere environments to improve the effectiveness of vermicompost immobilization of Cd.

Agricultural tillage practice and rhizosphere selection interactively drive the improvement of soybean plant biomass

Rhizosphere microbes play key roles in plant growth and productivity in agricultural systems. One of the critical issues is revealing the interaction of agricultural management (M) and rhizosphere selection effects (R) on soil microbial communities, root exudates and plant productivity. Through a field management experiment, we found that bacteria were more sensitive to the M × R interaction effect than fungi, and the positive effect of rhizosphere bacterial diversity on plant biomass existed in the bacterial three two-tillage system. In addition, inoculation experiments demonstrated that the nitrogen cycle-related isolate Stenotrophomonas could promote plant growth and alter the activities of extracellular enzymes N-acetyl- d-glucosaminidase and leucine aminopeptidase in rhizosphere soil. Microbe-metabolites network analysis revealed that hubnodes Burkholderia-Caballeronia-Paraburkholderia and Pseudomonas were recruited by specific root metabolites under the M × R interaction effect, and the inoculation of 10 rhizosphere-matched isolates further proved that these microbes could promote the growth of soybean seedlings. Kyoto Encyclopaedia of Genes and Genomes pathway analysis indicated that the growth-promoting mechanisms of these beneficial genera were closely related to metabolic pathways such as amino acid metabolism, melatonin biosynthesis, aerobactin biosynthesis and so on. This study provides field observation and experimental evidence to reveal the close relationship between beneficial rhizosphere microbes and plant productivity under the M × R interaction effect.

Unveiling a differential metabolite modulation of sorghum varieties under increasing tunicamycin-induced endoplasmic reticulum stress

Plants trigger endoplasmic reticulum (ER) pathways to survive stresses, but the assistance of ER in plant tolerance still needs to be explored. Thus, we selected sensitive and tolerant contrasting abiotic stress sorghum varieties to test if they present a degree of tolerance to ER stress. Accordingly, this work evaluated crescent concentrations of tunicamycin (TM µg mL-1): control (0), lower (0.5), mild (1.5), and higher (2.5) on the initial establishment of sorghum seedlings CSF18 and CSF20. ER stress promoted growth and metabolism reductions, mainly in CSF18, from mild to higher TM. The lowest TM increased SbBiP and SbPDI chaperones, as well as SbbZIP60, and SbbIRE1 gene expressions, but mild and higher TM decreased it. However, CSF20 exhibited higher levels of SbBiP and SbbIRE1 transcripts. It corroborated different metabolic profiles among all TM treatments in CSF18 shoots and similarities between profiles of mild and higher TM in CSF18 roots. Conversely, TM profiles of both shoots and roots of CSF20 overlapped, although it was not complete under low TM treatment. Furthermore, ER stress induced an increase of carbohydrates (dihydroxyacetone in shoots, and cellobiose, maltose, ribose, and sucrose in roots), and organic acids (pyruvic acid in shoots, and butyric and succinic acids in roots) in CSF20, which exhibited a higher degree of ER stress tolerance compared to CSF18 with the root being the most affected plant tissue. Thus, our study provides new insights that may help to understand sorghum tolerance and the ER disturbance as significant contributor for stress adaptation and tolerance engineering.

Breeding of Modern Rose Cultivars Decreases the Content of Important Biochemical Compounds in Rose Hips

This study aimed to determine the content and composition of bioactive compounds in autochthonous rose hips (R. pendulina, R. spinosissima, and R. gallica) and to compare them with the content of bioactive compounds in some cultivars ('Harstad', 'Bourgogne', 'Mount Everest', 'Poppius', 'Fruhlingsduft', 'Single Cherry', 'Fruhlingsmorgen', 'Violacea', and 'Splendens') derived from these main species. Due to insufficient information on how bioactive compound content changes when crossing roses, this study also sought to ascertain whether modern rose hip cultivars are still a sufficiently rich source of bioactive compounds and could, therefore, be potentially used as a functional food. All material was collected in the Arboretum Volčji Potok (Slovenia). The ascorbic acid content was highest in the 'Harstad' cultivar (12.79 g/kg FW), and the total organic acid content varied from 1.57 g/kg FW (R. spinosissima) to 34.39 g/kg FW ('Harstad'). Of all the carotenoids analyzed, only lycopene and β-carotene were present in all the samples. The total carotenoid content was highest in the 'Fruhlingsmorgen' cultivar (100.84 mg/kg FW), derived from R. spinosissima, and lowest in the main species, R. spinosissima (9.26 mg/kg FW). It can be concluded, therefore, that the content of bioactive compounds in rose hips of modern cultivars is generally lower than in rose hips of old cultivars and original species included in this study. The research results confirm that modern breeding strategies are mainly focused on goals such as abundant flowering and resistance to diseases and pests and not so much on the content of bioactive compounds.

Uncovering the Interrelation between Metabolite Profiles and Bioactivity of In Vitro- and Wild-Grown Catmint (Nepeta nuda L.)

Nepeta nuda L. is a medicinal plant enriched with secondary metabolites serving to attract pollinators and deter herbivores. Phenolics and iridoids of N. nuda have been extensively investigated because of their beneficial impacts on human health. This study explores the chemical profiles of in vitro shoots and wild-grown N. nuda plants (flowers and leaves) through metabolomic analysis utilizing gas chromatography and mass spectrometry (GC-MS). Initially, we examined the differences in the volatiles' composition in in vitro-cultivated shoots comparing them with flowers and leaves from plants growing in natural environment. The characteristic iridoid 4a-α,7-β,7a-α-nepetalactone was highly represented in shoots of in vitro plants and in flowers of plants from nature populations, whereas most of the monoterpenes were abundant in leaves of wild-grown plants. The known in vitro biological activities encompassing antioxidant, antiviral, antibacterial potentials alongside the newly assessed anti-inflammatory effects exhibited consistent associations with the total content of phenolics, reducing sugars, and the identified metabolic profiles in polar (organic acids, amino acids, alcohols, sugars, phenolics) and non-polar (fatty acids, alkanes, sterols) fractions. Phytohormonal levels were also quantified to infer the regulatory pathways governing phytochemical production. The overall dataset highlighted compounds with the potential to contribute to N. nuda bioactivity.

Dynamics of Organic Acids during the Droplet-Vitrification Cryopreservation Procedure Can Be a Signature of Oxidative Stress in Pogostemon yatabeanus

Cryopreservation in liquid nitrogen (LN, -196 °C) is a unique option for the long-term conservation of threatened plant species with non-orthodox or limitedly available seeds. In previous studies, a systematic approach was used to develop a droplet-vitrification (DV) cryopreservation protocol for Postemon yatabeanus shoot tips that includes preculture with 10% sucrose, osmoprotection with C4-35%, cryoprotection with A3-80% vitrification solution, and a three-step regrowth starting with the ammonium-free medium. The tricarboxylic acid (TCA) cycle is a crucial component of plant cell metabolism as it is involved in redox state regulation and energy provision. We hypothesized that organic acids (OAs) associated with the TCA and its side reactions indirectly indicate metabolism intensity and oxidative stress development in shoot tips under the cryopreservation procedure. In this study, the contents of 14 OAs were analyzed using gas chromatography-tandem mass spectrometry (GC-MS/MS) in P. yatabeanus shoot tips in a series of treatments including individual steps of the DV procedure, additional stress imposed by non-optimum protocol conditions (no preculture, no osmoprotection, various vitrification solution composition, using vials instead of aluminum foils, etc.) and regrowth on different media with or without ammonium or growth regulators. The possible relation of OA content with the total cryoprotectant (CPA) concentration and shoot tips regeneration percentage was also explored. Regeneration of cryopreserved shoot tips reduced in descending order as follows: standard protocol condition (91%) > non-optimum vitrification solution (ca. 68%) > non-optimum preculture (60-62%) > regrowth medium (40-64%) > no osmoprotection, cryopreservation in vials (28-30%). Five OAs (glycolic, malic, citric, malonic, and lactic) were the most abundant in the fresh (control) shoot tips. The dynamic pattern of OAs during the DV procedure highly correlated (r = 0.951) with the total CPA concentration employed: it gradually increased through the preculture, osmoprotection, and cryoprotection, peaked at cooling/rewarming (6.38-fold above control level), and returned to the fresh control level after 5 days of regrowth (0.89-fold). The contents of four OAs (2-hydroxybutyric, 3-hydroxypropionic, lactic, and glycolic) showed the most significant (10-209-fold) increase at the cooling/rewarming step. Lactic and glycolic acids were the major OAs at cooling/rewarming, accounting for 81% of the total OAs content. The OAs were categorized into three groups based on their dynamics during the cryopreservation protocol, and these groups were differently affected by protocol step modifications. However, there was no straightforward relationship between the dynamics of OAs and shoot tip regeneration. The results suggest that active modulation of OAs metabolism may help shoot tips to cope with osmotic stress and the chemical cytotoxicity\ of CPAs. Further intensive studies are needed to investigate the effect of cryopreservation on cell primarily metabolism and identify oxidative stress-related biomarkers in plant materials.

Gene regulation and ionome homeostasis in rice plants in response to arsenite stress: potential connection between transcriptomics and ionomics

Ionomics and transcriptomics were applied to demonstrate response of rice to arsenite [As(III)] stress in the current study. Rice plants were cultured in nutrient solutions treated with 0, 100 and 500 μg/L As(III) coded as CK, As1 and As5, respectively. The rice ionomes exhibited discriminatory response to environmental disturbances. Solid evidence of the effects of As(III) stress on binding, transport or metabolism of P, K, Ca, Zn and Cu was obtained in this work. Differentially expressed genes (DEGs) in the shoots were identified in three datasets: As1 vs CK, As5 vs CK and As5 vs As1. DEGs identified simultaneously in two or three datasets were selected for subsequent interaction and enrichment analyses. Upregulation of genes involved in protein kinase activity, phosphorus metabolic process and phosphorylation were detected in the rice treated with As(III), resulting in the maintenance of P homeostasis in the shoots. Zn and Ca binding genes were up-regulated since excess As inhibited the translocation of Zn and Ca from roots to shoots. Increased expression of responsive genes including HMA, WRKY, NAC and PUB genes conferred As tolerance in the rice plants to cope with external As(III) stress. The results suggested that As(III) stress could disturb the uptake and translocation of macro and essential elements by rice. Plants could regulate the expression of corresponding genes to maintain mineral nutrient homeostasis for essential metabolic processes.

Integrating Transcriptional, Metabolic, and Physiological Responses to Drought Stress in Ilex paraguariensis Roots

The appearance of water stress episodes triggers leaf abscission and decreases Ilex paraguariensis yield. To explore the mechanisms that allow it to overcome dehydration, we investigated how the root gene expression varied between water-stressed and non-stressed plants and how the modulation of gene expression was linked to metabolite composition and physiological status. After water deprivation, 5160 differentially expressed transcripts were obtained through RNA-seq. The functional enrichment of induced transcripts revealed significant transcriptional remodelling of stress-related perception, signalling, transcription, and metabolism. Simultaneously, the induction of the enzyme 9-cis-expoxycarotenoid dioxygenase (NCED) transcripts reflected the central role of the hormone abscisic acid in this response. Consequently, the total content of amino acids and soluble sugars increased, and that of starch decreased. Likewise, osmotic adjustment and radical growth were significantly promoted to preserve cell membranes and water uptake. This study provides a valuable resource for future research to understand the molecular adaptation of I. paraguariensis plants under drought conditions and facilitates the exploration of drought-tolerant candidate genes.

Oxalic-activated minerals enhance the stabilization of polypropylene and polyamide microplastics in soil: Crucial roles of mineral dissolution coupled surface oxygen-functional groups

Low-molecular-weight organic acids (LMWOAs) prevalent in soil environments may influence the transport, fate, and orientation of microplastics (MPs) by mediating mineral interfaces. Nevertheless, few studies have reported their impact on the environmental behavior of MPs in soil. Here, the functional regulation of oxalic at mineral interfaces and its stabilizing mechanism for MPs were investigated. The results showed that oxalic drove MPs stability onto minerals and new adsorption pathways, which are dependent on the bifunctionality of minerals induced by oxalic acid. Besides, our findings reveal that in the absence of oxalic acid, the stability of hydrophilic and hydrophobic MPs on kaolinite (KL) mainly displays hydrophobic dispersion, whereas electrostatic interaction is dominant on ferric sesquioxide (FS). Moreover, the amide functional groups ([NHCO]) of PA-MPs may have positive feedback on the stability of MPs. In the presence of oxalic acid (2-100 mM), the MPs stability efficiency and property onto minerals were integrally increased in batch studies. Our results demonstrate the oxalic acid-activated interfacial interaction of minerals via dissolution coupled O-functional groups. Oxalic-induced functionality at mineral interfaces further activates electrostatic interaction, cation bridge effect, hydrogen forces, ligand exchange and hydrophobicity. These findings provide new insights into the regulating mechanisms of oxalic-activated mineral interfacial properties for environmental behavior of emerging pollutants.

Synergistic Effect of Melatonin and Lysinibacillus fusiformis L. (PLT16) to Mitigate Drought Stress via Regulation of Hormonal, Antioxidants System, and Physio-Molecular Responses in Soybean Plants

Drought is one of the most detrimental factors that causes significant effects on crop development and yield. However, the negative effects of drought stress may be alleviated with the aid of exogenous melatonin (MET) and the use of plant-growth-promoting bacteria (PGPB). The present investigation aimed to validate the effects of co-inoculation of MET and Lysinibacillus fusiformis on hormonal, antioxidant, and physio-molecular regulation in soybean plants to reduce the effects of drought stress. Therefore, ten randomly selected isolates were subjected to various plant-growth-promoting rhizobacteria (PGPR) traits and a polyethylene-glycol (PEG)-resistance test. Among these, PLT16 tested positive for the production of exopolysaccharide (EPS), siderophore, and indole-3-acetic acid (IAA), along with higher PEG tolerance, in vitro IAA, and organic-acid production. Therefore, PLT16 was further used in combination with MET to visualize the role in drought-stress mitigation in soybean plant. Furthermore, drought stress significantly damages photosynthesis, enhances ROS production, and reduces water stats, hormonal signaling and antioxidant enzymes, and plant growth and development. However, the co-application of MET and PLT16 enhanced plant growth and development and improved photosynthesis pigments (chlorophyll a and b and carotenoids) under both normal conditions and drought stress. This may be because hydrogen-peroxide (H2O2), superoxide-anion (O2-), and malondialdehyde (MDA) levels were reduced and antioxidant activities were enhanced to maintain redox homeostasis and reduce the abscisic-acid (ABA) level and its biosynthesis gene NCED3 while improving the synthesis of jasmonic acid (JA) and salicylic acid (SA) to mitigate drought stress and balance the stomata activity to maintain the relative water states. This may be possible due to a significant increase in endo-melatonin content, regulation of organic acids, and enhancement of nutrient uptake (calcium, potassium, and magnesium) by co-inoculated PLT16 and MET under normal conditions and drought stress. In addition, co-inoculated PLT16 and MET modulated the relative expression of DREB2 and TFs bZIP while enhancing the expression level of ERD1 under drought stress. In conclusion, the current study found that the combined application of melatonin and Lysinibacillus fusiformis inoculation increased plant growth and could be used to regulate plant function during drought stress as an eco-friendly and low-cost approach.

Plant phosphate status influences root biotic interactions

Phosphorus (P) deficiency stress in combination with biotic stress(es) severely impacts crop yield. Plant responses to P deficiency overlapping with that of other stresses exhibit a high degree of complexity involving different signaling pathways. On the one hand, plants engage with rhizosphere microbiome/arbuscular mycorrhizal fungi for improved phosphate (Pi) acquisition and plant stress response upon Pi deficiency; on the other hand, this association is gets disturbed under Pi sufficiency. This nutrient-dependent response is highly regulated by the phosphate starvation response (PSR) mediated by the master regulator, PHR1, and its homolog, PHL. It is interesting to note that Pi status (deficiency/sufficiency) has a varying response (positive/negative) to different biotic encounters (beneficial microbes/opportunistic pathogens/insect herbivory) through a coupled PSR-PHR1 immune system. This also involves crosstalk among multiple players including transcription factors, defense hormones, miRNAs, and Pi transporters, among others influencing the plant-biotic-phosphate interactions. We provide a comprehensive view of these key players involved in maintaining a delicate balance between Pi homeostasis and plant immunity. Finally, we propose strategies to utilize this information to improve crop resilience to Pi deficiency in combination with biotic stresses.

Multi-omics-based identification of purple acid phosphatases and metabolites involved in phosphorus recycling in stylo root exudates

Stylo (Stylosanthes guianensis) is a tropical forage and cover crop that possesses low phosphate (Pi) tolerance traits. However, the mechanisms underlying its tolerance to low-Pi stress, particularly the role of root exudates, remain unclear. This study employed an integrated approach using physiological, biochemical, multi-omics, and gene function analyses to investigate the role of stylo root exudates in response to low-Pi stress. Widely targeted metabolomic analysis revealed that eight organic acids and one amino acid (L-cysteine) were significantly increased in the root exudates of Pi-deficient seedlings, among which tartaric acid and L-cysteine had strong abilities to dissolve insoluble-P. Furthermore, flavonoid-targeted metabolomic analysis identified 18 flavonoids that were significantly increased in root exudates under low-Pi conditions, mainly belonging to the isoflavonoid and flavanone subclasses. Additionally, transcriptomic analysis revealed that 15 genes encoding purple acid phosphatases (PAPs) had upregulated expression in roots under low-Pi conditions. Among them, SgPAP10 was characterized as a root-secreted phosphatase, and overexpression of SgPAP10 enhanced organic-P utilization by transgenic Arabidopsis. Overall, these findings provide detailed information regarding the importance of stylo root exudates in adaptation to low-Pi stress, highlighting the plant's ability to release Pi from organic-P and insoluble-P sources through root-secreted organic acids, amino acids, flavonoids, and PAPs.

Abiotic Stress in Crop Production

The vast majority of agricultural land undergoes abiotic stress that can significantly reduce agricultural yields. Understanding the mechanisms of plant defenses against stresses and putting this knowledge into practice is, therefore, an integral part of sustainable agriculture. In this review, we focus on current findings in plant resistance to four cardinal abiotic stressors—drought, heat, salinity, and low temperatures. Apart from the description of the newly discovered mechanisms of signaling and resistance to abiotic stress, this review also focuses on the importance of primary and secondary metabolites, including carbohydrates, amino acids, phenolics, and phytohormones. A meta-analysis of transcriptomic studies concerning the model plant Arabidopsis demonstrates the long-observed phenomenon that abiotic stressors induce different signals and effects at the level of gene expression, but genes whose regulation is similar under most stressors can still be traced. The analysis further reveals the transcriptional modulation of Golgi-targeted proteins in response to heat stress. Our analysis also highlights several genes that are similarly regulated under all stress conditions. These genes support the central role of phytohormones in the abiotic stress response, and the importance of some of these in plant resistance has not yet been studied. Finally, this review provides information about the response to abiotic stress in major European crop plants—wheat, sugar beet, maize, potatoes, barley, sunflowers, grapes, rapeseed, tomatoes, and apples.

Metabolic Profiling Identifies Changes in the Winter Wheat Grains Following Fusarium Treatment at Two Locations in Croatia

Fusarium head blight (FHB) is one of the most dangerous diseases of winter wheat, resulting in reduced grain yield and quality, and production of mycotoxins by the Fusarium fungi. In the present study, changes in the grain metabolomics of winter wheat samples infected with Fusarium spp. and corresponding non-infected samples from two locations in Croatia were investigated by GC-MS. A Mann-Whitney test revealed that 24 metabolites detected were significantly separated between Fusarium-inoculated and non-infected samples during the variety by treatment interactions. The results confirmed that in grains of six FHB-resistant varieties, ten metabolites were identified as possible resistance-related metabolites. These metabolites included heptadecanoic acid, 9-(Z)-hexadecenoic acid, sophorose, and secolaganin in grains of FHB-resistant varieties at the Osijek location, as well as 2-methylaminomethyltartronic acid, maleamic acid, 4-hydroxyphenylacetonitrile, 1,4-lactonearabinonic acid, secolaganin, and alanine in grains of FHB-resistant varieties at the Tovarnik location. Moreover, on the PCA bi-plot, FHB-susceptible wheat varieties were closer to glycyl proline, decanoic acid, and lactic acid dimer that could have affected other metabolites, and thus, suppressed resistance to FHB. Although defense reactions were genetically conditioned and variety specific, resulting metabolomics changes may give insight into defense-related pathways that could be manipulated to engineer plants with improved resistance to the pathogen.

Plant rhizosphere defense system respond differently to emerging polyfluoroalkyl substances F-53B and PFOS stress

Chlorinated polyfluoroalkyl ether sulfonate (F-53B) and perfluorooctanesulfonate (PFOS) are used and emitted as fog inhibitors in the chromium plating industry, and they are widely detected worldwide. To study the effects of F-53B and PFOS on the rhizosphere defense system, they were added at two levels (0.1 and 50 mg L^-1) to the soil where different plants (Lythrum salicaria and Phragmites communis) were grown. In bulk soils, high concentrations of F-53B/PFOS resulted in significant increases in soil pH, NH₄⁺-N, and NO₃^--N (the effect of PFOS on NO₃^--N was not significant). Moreover, the extent of the effects of PFOS and F-53B on the physicochemical properties of bulk soils were different (e.g., PFOS caused an increase of NH₄⁺-N by 8.94%-45.97% compared to 1.63%-25.20% for F-53B). Root exudates and PFASs together influenced the physicochemical properties of rhizosphere soils (e.g., TOC increased significantly in contaminated rhizosphere soils but did not change in non-bulk soils). Under the influence of F-53B/PFOS, the root exudates regulated by plants were changed and weakened the effect of F-53B/PFOS on microbial community of rhizosphere soil. The rhizosphere defense systems of different plants have both similarities and differences in response to different substances and concentrations.

The multifaceted roles of Arbuscular Mycorrhizal Fungi in peanut responses to salt, drought, and cold stress

BACKGROUND

Arbuscular Mycorrhizal Fungi (AMF) are beneficial microorganisms in soil-plant interactions; however, the underlying mechanisms regarding their roles in legumes environmental stress remain elusive. Present trials were undertaken to study the effect of AMF on the ameliorating of salt, drought, and cold stress in peanut (Arachis hypogaea L.) plants. A new product of AMF combined with Rhizophagus irregularis SA, Rhizophagus clarus BEG142, Glomus lamellosum ON393, and Funneliformis mosseae BEG95 (1: 1: 1: 1, w/w/w/w) was inoculated with peanut and the physiological and metabolomic responses of the AMF-inoculated and non-inoculated peanut plants to salt, drought, and cold stress were comprehensively characterized, respectively.

RESULTS

AMF-inoculated plants exhibited higher plant growth, leaf relative water content (RWC), net photosynthetic rate, maximal photochemical efficiency of photosystem II (PSII) (Fv/Fm), activities of antioxidant enzymes, and K⁺: Na⁺ ratio while lower leaf relative electrolyte conductivity (REC), concentration of malondialdehyde (MDA), and the accumulation of reactive oxygen species (ROS) under stressful conditions. Moreover, the structures of chloroplast thylakoids and mitochondria in AMF-inoculated plants were less damaged by these stresses. Non-targeted metabolomics indicated that AMF altered numerous pathways associated with organic acids and amino acid metabolisms in peanut roots under both normal-growth and stressful conditions, which were further improved by the osmolytes accumulation data.

CONCLUSION

This study provides a promising AMF product and demonstrates that this AMF combination could enhance peanut salt, drought, and cold stress tolerance through improving plant growth, protecting photosystem, enhancing antioxidant system, and regulating osmotic adjustment.

Seasonal Variations of Low-Molecular-Weight Organic Acids in Three Evergreen Broadleaf Rhododendron Forests

Low-molecular-weight organic acids (LMWOAs) are widely distributed in forests. Fresh leaves, litter, humus, and the topsoil layer of representative Rhododendron delavayi (RD), Rhododendron agastum (RA), and Rhododendron irroratum (RI) in the Baili Rhododendron National Forest Park were sampled to explore their seasonal changes. The contents of oxalic, tartaric, malic, citric, acetic, lactic, succinic, and formic acids in samples from different seasons were determined by high-performance liquid chromatography. The results showed that the composition and content of the LMWOAs in the fresh leaves, litter, humus, and topsoil layer of the rhododendrons were affected by the tree species, samples, and season. The main LMWOA was oxalic acid (the average content in the samples was 195.31 µg/g), followed by malic acid (the average content in the samples was 68.55 µg/g) and tartaric acid (the average content in the samples was 59.82 µg/g). Succinic acid had the lowest content; the average content in the samples was 18.40 µg/g. The LMWOAs of the RD were the highest (the average content in the samples was 517.42 µg/g), and the LMWOAs of the RI were the lowest (the average content in the samples was 445.18 µg/g). The LMWOAs in the three rhododendron forests were in the order of fresh leaves > litter > humus > soil layers. This study showed the seasonal distribution characteristics of LMWOAs in three evergreen broadleaf rhododendron forests, and the results provide a reference for ecosystem management and the protection of wild rhododendron forests.

Pristine and sulfidized zinc oxide nanoparticles alter bacterial communities and metabolite profiles in soybean rhizocompartments

A better understanding of bacterial communities and metabolomic responses to pristine zinc oxide manufacture nanoparticles (ZnO MNPs) and its sulfidized product (s-ZnO MNPs), as well as their corresponding Zn ions in rhizocompartments, critical in the plant-microbe interactions, could contribute to the sustainable development of nano-enabled agriculture. In this study, soybean (Glycine max) were cultivated in soils amended with three Zn forms, namely ZnSO₄·7H₂O, ZnO MNPs and s-ZnO MNPs at 0, 100 and 500 mg·kg^-1 for 70 days. Three Zn forms exposures profoundly decreased the bacterial alpha diversity in roots and nodules. High dose (500 mg·kg^-1) groups had a stronger impact on the bacterial beta diversity than low dose (100 mg·kg^-1) groups. In the rhizosphere soil and roots, 500 mg·kg^-1 of ZnSO₄ and s-ZnO MNPs treatments showed the largest shifts in bacterial community structure, respectively. In addition, several significant changed bacterial taxa and metabolites were found at the high dose groups, which were associated with carbon and nitrogen metabolism. PLS-DA plot showed good discrimination in metabolomic profiles of rhizosphere soil and roots between three Zn forms treatments and control. Most metabolic pathways perturbed were closely linked to oxidative stress. Overall, our study indicates either dissolved or nano-particulate Zn exposure at high dose can drastically affected bacterial communities and metabolite profiles in soybean rhizocompartments.

Differences in Carbon Sequestration Ability of Diverse Tartary Buckwheat Genotypes in Barren Soil Caused by Microbial Action

Planting plants to increase soil carbon input has been widely used to achieve carbon neutrality goals. Tartary buckwheat not only has good barren tolerance but is also rich in nutrients and very suitable for planting in barren areas. However, the effects of different genotypes of Tartary buckwheat roots and rhizosphere microorganisms on soil carbon input are still unclear. In this study, ozone sterilization was used to distinguish the sources of soil organic acids and C-transforming enzymes, and the contribution of root and rhizosphere microorganisms to soil carbon storage during the growth period of two genotypes of tartary buckwheat was studied separately to screen suitable varieties. Through the analysis of the experimental results, the conclusions are as follows: (1) The roots of Diqing tartary buckwheat have stronger carbon sequestration ability in a barren environment than Heifeng, and the microorganisms in Diqing tartary buckwheat soil will also increase soil carbon input. Therefore, Diqing tartary buckwheat is more suitable for carbon sequestration than Heifeng tartary buckwheat in barren soil areas. (2) In the absence of microorganisms, the rhizosphere soil of tartary buckwheat can regulate the storage of soil organic carbon by secreting extracellular enzymes and organic acids. (3) The structural equation model showed that to promote carbon sequestration, Heifeng tartary buckwheat needed to inhibit microbial action when planted in the barren area of Loess Plateau, while Diqing tartary buckwheat needed to use microbial-promoting agents. Adaptive strategies should focus more on cultivar selection to retain carbon in soil and to assure the tolerance of fineness in the future.

Single and combined toxicity of polystyrene nanoplastics and arsenic on submerged plant Myriophyllum verticillatum L

The contamination of nanoplastics (NPs) and heavy metals (HM) in water bodies has caused widespread concern, while their effects on submerged plants are poorly reported. Polystyrene nanoplastics (PSNPs) and arsenic (As) were used to assess their toxicity on Myriophyllum verticillatum L. via the orthogonal experiments. PSNPs significantly reduced the accumulation of As (17.24%-66.67%) in plant. Single As and high As-PSNPs treatments significantly inhibited plant growth, with a maximum reduction of 70.09% in the growth rate. The mineral nutrient content was significantly affected by PSNPs and As treatments. The antioxidant system was significantly inhibited, which was more pronounced in the roots. Similar findings were observed for soluble protein and soluble sugar. Some organic acids and amino acids showed down-regulation at high concentrations of As, leading to a decrease in the content of the mineral element and down-regulation of antioxidant enzyme synthesis. Furthermore, PSNPs could alleviate As toxicity under 0.1 mg/L As treatment but exacerbate As toxicity at 1 mg/L As dose. This study has important implications for the study of submerged plants exposed to co-contamination of microplastics and heavy metals, as well as the possible ecological risk assessment in freshwater.

Evaluation of eleven kiwifruit genotypes for bicarbonate tolerance and characterization of two tolerance-contrasting genotypes

Screening bicarbonate-tolerant genotypes is an environmentally-friendly and long-term effective strategy to cope with bicarbonate-induced chlorosis in fruit crops grown on calcareous soils. We investigated eleven genotypes from four kiwifruit species (Actinidia chinensis, A. macrosperma, A. polygama, and A. valvata) for differences in bicarbonate tolerance. We also characterized the physiological and molecular differences in two contrasting genotypes of this group. In the first experiment, bicarbonate-treated plantlets were irrigated with 3.0 g L^-1 CaCO₃ and 5.04 g L^-1 NaHCO₃ in peat and perlite medium culture. Based on principal component analysis, weight-based membership function method and cluster analysis, the tested genotypes were classified into three groups: (1) tolerant, including YX, Av-1, Acd, Ap, Av-2, and QM; (2) moderately tolerant, including Av-3, Am, Av-4, and HWD; and (3) sensitive, including only QH. In the second experiment, QH (bicarbonate-sensitive) and YX (bicarbonate-tolerant) were grown in sand culture with 4.0 g L^-1 CaCO₃ and 0.84 g L^-1 or 1.26 g L^-1 NaHCO₃. Compared with QH, YX showed a better ability to take up iron (Fe) by roots and to transport Fe from roots to shoots in the bicarbonate treatments, probably due to a better capacity to protect from oxidative damage and to excrete protons, and a differential expression of genes associated with Fe uptake and translocation, including HA8, IRT1, YSL3 and NRAMP3. The results can facilitate identifying potential resources for bicarbonate tolerance and breeding new rootstocks, and contribute to the elucidation of the bicarbonate tolerance mechanisms in the genus Actinidia.

Metabolomic Analysis Reveals the Effect of Insecticide Chlorpyrifos on Rice Plant Metabolism

Pesticides as important agricultural inputs play a vital role in protecting crop plants from diseases and pests; however, the effect of pesticides on crop plant physiology and metabolism is still undefined. In this study, the effect of insecticide chlorpyrifos at three doses on rice plant physiology and metabolism was investigated. Our results revealed that chlorpyrifos cause oxidative stress in rice plants and even inhibit plant growth and the synthesis of protein and chlorophyll at high doses. The metabolomic results suggested that chlorpyrifos could affect the metabolic profiling of rice tissues and a total of 119 metabolites with significant changes were found, mainly including organic acids, amino acids, lipids, polyphenols, and flavonoids. Compared to the control, the content of glutamate family amino acids were significantly disturbed by chlorpyrifos, where defense-related proline and glutathione were significantly increased; however, glutamic acid, N-acetyl-glutamic acid and N-methyl-glutamic acid were significantly decreased. Many unsaturated fatty acids, such as linolenic acid and linoleic acid, and their derivatives lysophospholipids and phospholipids, were significantly accumulated in chlorpyrifos groups, which could act as osmolality substances to help rice cells relieve chlorpyrifos stress. Three organic acids, aminobenzoic acid, quinic acid, and phosphoenolpyruvic acid, involved in plant defenses, were significantly accumulated with the fold change ranging from 1.32 to 2.19. In addition, chlorpyrifos at middle- and high-doses caused the downregulation of most flavonoids. Our results not only revealed the effect of insecticide chlorpyrifos on rice metabolism, but also demonstrated the value of metabolomics in elucidating the mechanisms of plant responses to stresses.