Silicon Alleviate Hypoxia Stress by Improving Enzymatic and Non-enzymatic Antioxidants and Regulating Nutrient Uptake in Muscadine Grape (Muscadinia rotundifolia Michx.)

Different Phenotypic, Photosynthetic, and Physiological Responses to Flooding between Q. nuttallii and Q. palustris

Flooding stress is an increasingly serious problem in wetlands, often affecting large areas of crops and timber production areas. The current study aimed to explore the species differences in responses to flooding stress between Q. nuttallii and Q. palustris in an outdoor environment. All the tested plants survived after a 60-day flooding treatment that left 5 cm of water above the soil surface. This suggests that the two species are flood-tolerant, so they can be applied in the construction of riparian protection forests and wetland restoration. Compared with control conditions, flooding treatment significantly decreased seedling height and diameter and the Pn, Gs, Tr, Fv/Fm, ABS/CSm, TR0/CSm, ET0/CSm, RE0/CSm, IAA, and GA3 content and significantly increased the content of MDA, H2O2, soluble sugars, SOD, POD, ADH, ABA, and JA. Under control conditions, Q. nuttallii showed significantly greater growth and photosynthetic capability than Q. palustris. In contrast, Q. palustris exhibited less inhibition of growth and photosynthesis, oxidative stress levels, and antioxidant enzyme activities than Q. nuttallii under flooding conditions. The findings indicate that Q. palustris has better defense mechanisms against the damage caused by flooding stress than Q. nuttallii. Q. nuttallii was more sensitive and responsive to flooding than Q. palustris.

Foliar application protected vegetable against poisonous element cadmium and mitigated human health risks

Foliar application has been reported as an effective method to facilitate plant growth and mitigate cadmium (Cd) accumulation. However, the application of foliar fertilizers on plant production, Cd uptake and health risks of Solanaceae family remains unknown. In this study, four foliar fertilizers were applied to investigate their effects on the production, Cd accumulation and human health risk assessment of two varieties of pepper (Capsicum annuum L.) and eggplant (Solanum melongena L.), respectively. Compared with CK, the foliar application increased vegetable production to 104.16 %-123.70 % in peppers, and 100.83 %-105.17 % in eggplants, accordingly. The application of foliar fertilizers largely decreased Cd TF (transportation factor) by up to 23.32 % in JY, 18.37 % in GJ of pepper varieties, and up to 14.47 % in ZL, 15.24 % in HGR of eggplant varieties. Moreover, Cd BAF (bioaccumulation factor) also declined to different extents after the application of foliar fertilizers. As for human health risk assessments, foliar application diminished the hazard index (HI) and carcinogenic risk (CR) of both pepper and eggplant varieties. The results concluded that the application of composed foliar fertilizers was most effective, and could be a promising alternative for the improvement of vegetable production and mitigation of vegetable Cd accumulation and human health risks as well. The results further highlighted the understanding of foliar fertilizer application on vegetable production and health risks, which benefited better vegetable safe production and further guaranteed human health.

Foliar spraying of exogenous uniconazole (S3307) at the flowering stage as an effective method to resist low-temperature stress on mung bean [Vigna radiata (L.) Wilczek]

Low temperature is one of the major constraints on agricultural productivity worldwide and is likely to further increase. Several adaptations and mitigation strategies are required to cope with low-temperature stress. Uniconazole (S3307) could play a significant role in the alleviation of abiotic stress in plants. In this study, the effects of S3307 on the reactive oxygen species (ROS) and antioxidant metabolism were studied in the leaves of mung bean [Vigna radiata (L.) Wilczek]. The experimental results showed that the low-temperature induced accumulation of superoxide anion (O2-) production rate, and malonaldehyde (MDA) contents. Increased proline content and enzymatic antioxidants, including superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), were found to alleviate oxidative damage under low temperatures. While, S3307 could reduce O2- production rate and MDA contents and increase the activities of SOD, POD, and CAT, slowed the decrease in ascorbic acid (AsA), dehydroascorbic acid (DHA), glutathione (GSH), and oxidized glutathione (GSSG), and promoted increase in soluble sugars (SS), soluble proteins (SP), and proline (Pro) content under low-temperature. At the same time, low temperature leads to lower 100 grain weight and number of grains per plant, which eventually causes yield reduction decreased. Foliar spraying of S3307 could alleviate the yield loss caused by low temperature, and the increase of S3307 treatment was 5.1%-12.5% and 6.3%-32.9% for the two varieties, respectively, compared with CK. In summary, exogenous S3307 pretreatment enhances plant tolerance to low-temperature by improving the antioxidant enzyme activities, increased non-enzymatic antioxidants content, and decreased O2- production rate and MDA contents and inducing alterations in endogenous S3307, and reduce the decrease in mung bean yield.

Silicon-based nanoparticles for mitigating the effect of potentially toxic elements and plant stress in agroecosystems: A sustainable pathway towards food security

Due to their size, flexibility, biocompatibility, large surface area, and variable functionality nanoparticles have enormous industrial, agricultural, pharmaceutical and biotechnological applications. This has led to their widespread use in various fields. The advancement of knowledge in this field of research has altered our way of life from medicine to agriculture. One of the rungs of this revolution, which has somewhat reduced the harmful consequences, is nanotechnology. A helpful ingredient for plants, silicon (Si), is well-known for its preventive properties under adverse environmental conditions. Several studies have shown how biogenic silica helps plants recover from biotic and abiotic stressors. The majority of research have demonstrated the benefits of silicon-based nanoparticles (Si-NPs) for plant growth and development, particularly under stressful environments. In order to minimize the release of brine, heavy metals, and radioactive chemicals into water, remove metals, non-metals, and radioactive components, and purify water, silica has also been used in environmental remediation. Potentially toxic elements (PTEs) have become a huge threat to food security through their negative impact on agroecosystem. Si-NPs have the potentials to remove PTEs from agroecosystem and promote food security via the promotion of plant growth and development. In this review, we have outlined the various sources and ecotoxicological consequences of PTEs in agroecosystems. The potentials of Si-NPs in mitigating PTEs were extensively discussed and other applications of Si-NPs in agriculture to foster food security were also highlighted.

Emerging Frontiers in Nanotechnology for Precision Agriculture: Advancements, Hurdles and Prospects

This review article provides an extensive overview of the emerging frontiers of nanotechnology in precision agriculture, highlighting recent advancements, hurdles, and prospects. The benefits of nanotechnology in this field include the development of advanced nanomaterials for enhanced seed germination and micronutrient supply, along with the alleviation of biotic and abiotic stress. Further, nanotechnology-based fertilizers and pesticides can be delivered in lower dosages, which reduces environmental impacts and human health hazards. Another significant advantage lies in introducing cutting-edge nanodiagnostic systems and nanobiosensors that monitor soil quality parameters, plant diseases, and stress, all of which are critical for precision agriculture. Additionally, this technology has demonstrated potential in reducing agro-waste, synthesizing high-value products, and using methods and devices for tagging, monitoring, and tracking agroproducts. Alongside these developments, cloud computing and smartphone-based biosensors have emerged as crucial data collection and analysis tools. Finally, this review delves into the economic, legal, social, and risk implications of nanotechnology in agriculture, which must be thoroughly examined for the technology’s widespread adoption.

Exogenous zinc mitigates salinity stress by stimulating proline metabolism in proso millet (Panicum miliaceum L.)

Salinity is one of the most concerning ecological restrictions influencing plant growth, which poses a devastating threat to global agriculture. Surplus quantities of ROS generated under stress conditions have negative effects on plants' growth and survival by damaging cellular components, including nucleic acids, lipids, proteins and carbohydrates. However, low levels of ROS are also necessary because of their role as signalling molecules in various development-related pathways. Plants possess sophisticated antioxidant systems for scavenging as well as regulating ROS levels to protect cells from damage. Proline is one such crucial non-enzymatic osmolyte of antioxidant machinery that functions in the reduction of stress. There has been extensive research on improving the tolerance, effectiveness, and protection of plants against stress, and to date, various substances have been used to mitigate the adverse effects of salt. In the present study Zinc (Zn) was applied to elucidate its effect on proline metabolism and stress-responsive mechanisms in proso millet. The results of our study indicate the negative impact on growth and development with increasing treatments of NaCl. However, the low doses of exogenous Zn proved beneficial in mitigating the effects of NaCl by improving morphological and biochemical features. In salt-treated plants, the low doses of Zn (1 mg/L, 2 mg/L) rescued the negative impact of salt (150mM) as evidenced by increase in shoot length (SL) by 7.26% and 25.5%, root length (RL) by 21.84% and 39.07% and membrane stability index (MSI) by 132.57% and 151.58% respectively.The proline content improved at all concentrations with maximum increase of 66.65% at 2 mg/L Zn. Similarly, the low doses of Zn also rescued the salt induced stress at 200mM NaCl. The enzymes related to proline biosynthesis were also improved at lower doses of Zn. In salt treated plants (150mM), Zn (1 mg/L, 2 mg/L) increased the activity of P5CS by 19.344% and 21%. The P5CR and OAT activities were also improved with maximum increase of 21.66% and 21.84% at 2 mg/L Zn respectively. Similarly, the low doses of Zn also increased the activities of P5CS, P5CR and OAT at 200mM NaCl. Whereas P5CDH enzyme activity showed a decrease of 82.5% at 2mg/L Zn+150mM NaCl and 56.7% at 2mg/L Zn+200 mM NaCl. These results strongly imply the modulatory role of Zn in maintaining of proline pool during NaCl stress.

Physiological and comparative transcriptome analysis of the response and adaptation mechanism of the photosynthetic function of mulberry (Morus alba L.) leaves to flooding stress

Flooding has become one of the major abiotic stresses that seriously affects plant growth and development owing to changes in the global precipitation pattern. Mulberry (Morus alba L.) is a desirable tree spePhysocarpus amurensis Maxim andcies with high ecological and economic benefits. To reveal the response and adaptive mechanisms of the photosynthetic functions of mulberry leaves to flooding stress, chlorophyll synthesis, photosynthetic electron transfer and the Calvin cycle were investigated by physiological studies combined with an analysis of the transcriptome. Flooding stress inhibited the synthesis of chlorophyll (Chl) and decreased its content in mulberry leaves. The sensitivity of Chl a to flooding stress was higher than that of Chl b owing to the changes of CHLG (LOC21385082) and CAO (LOC21408165) that encode genes during chlorophyll synthesis. The levels of expression of Chl b reductase NYC (LOC112094996) and NYC (LOC21385774), which are involved in Chl b degradation, were upregulated on the fifteenth day of flooding, which accelerated the transformation of Chl b to Chl a, and upregulated the expression of PPH (LOC21385040) and PAO (LOC21395013). This accelerated the degradation of chlorophyll. Flooding stress significantly inhibited the photosynthetic function of mulberry leaves. A Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of differentially expressed genes under different days of flooding stress indicated significant enrichment in Photosynthesis-antenna proteins (map00196), Photosynthesis (map00195) and Carbon fixation in photosynthetic organisms (map00710). On the fifth day of flooding, 7 and 5 genes that encode antenna proteins were identified on LHCII and LHCI, respectively. They were significantly downregulated, and the degree of downregulation increased as the trees were flooded longer. Therefore, the power of the leaves to capture solar energy and transfer this energy to the reaction center was reduced. The chlorophyll fluorescence parameters and related changes in the expression of genes in the transcriptome indicated that the PSII and PSI of mulberry leaves were damaged, and their activities decreased under flooding stress. On the fifth day of flooding, electron transfer on the PSII acceptor side of mulberry leaves was blocked, and the oxygen-evolving complex (OEC) on the donor side was damaged. On the tenth day of flooding, the thylakoid membranes of mulberry leaves were damaged. Five of the six coding genes that mapped to the OEC were significantly downregulated. Simultaneously, other coding genes located at the PSII reaction center and those located at the PSI reaction center, including Cytb6/f, PC, Fd, FNR and ATP, were also significantly downregulated. In addition, the gas exchange parameters (P_n, G_s, T_r, and C_i) of the leaves decreased after 10 days of flooding stress primarily owing to the stomatal factor. However, on the fifteenth day of flooding, the value for the intracellular concentration of CO₂ was significantly higher than that on the tenth day of flooding. In addition, the differentially expressed genes identified in the Calvin cycle were significantly downregulated, suggesting that in addition to stomatal factors, non-stomatal factors were also important factors that mediated the decrease in the photosynthetic capacity of mulberry leaves. In conclusion, the inhibition of growth of mulberry plants caused by flooding stress was primarily related to the inhibition of chlorophyll synthesis, antenna proteins, photosynthetic electron transfer and the Calvin cycle. The results of this study provide a theoretical basis for the response and mechanism of adaptation of the photosynthetic function of mulberry to flooding stress.

Silicon nanoforms in crop improvement and stress management

Although, silicon - the second most abundant element in the earth crust could not supersede carbon (C) in the competition of being the building block of life during evolution, yet its presence has been reported in some life forms. In case of the plants, silicon has been reported widely to promote the plant growth under normal as well as stressful situations. Nanoform of silicon is now being explored for its potential to improve plant productivity and its tolerance against various stresses. Silicon nanoparticles (SiNPs) in the form of nanofertilizers, nanoherbicides, nanopesticides, nanosensors and targeted delivery systems, find great utilization in the field of agriculture. However, the mechanisms underlying their uptake by plants need to be deciphered in detail. Silicon nanoformss are reported to enhance plant growth, majorly by improving photosynthesis rate, elevating nutrient uptake and mitigating reactive oxygen species (ROS)-induced oxidative stress. Various studies have reported their ability to provide tolerance against a range of stresses by upregulating plant defense responses. Moreover, they are proclaimed not to have any detrimental impacts on environment yet. This review includes the up-to-date information in context of the eminent role of silicon nanoforms in crop improvement and stress management, supplemented with suggestions for future research in this field.

Endofungal Rhizobium species enhance arsenic tolerance in colonized host plant under arsenic stress

Arsenic (As) is a toxic metalloid that is present in natural surroundings in many forms with severe consequences to sustainable agriculture and human health. Plant growth-promoting Rhizobia have been found involved in the induction of plant tolerance under various biotic and abiotic stresses. An endofungal Rhizobium species associated with arbuscular mycorrhizal fungi (AMF) Serendipita indica deploy beneficial role in the promotion of plant growth and tolerance against various biotic and abiotic stresses. In the current study, we have determined the role of endofungal Rhizobium species in protection of host plant growth under As stress. We observed that endofungal Rhizobium species strain Si001 tolerate AsV up to 25 mM and its inoculation enhances tomato seed germination and seedling growth. A hyper-colonization of Rhizobium species Si001 in tomato roots was observed under As stress and results in modulation of GSH and proline content with reduced ROS. Rhizobium species Si001 colonization in host plant recovered pigment contents (chlorophyll-a and chlorophyll-b up to 189.5% and 192%, respectively), photosynthesis (157%), and water use efficiency (166%) compared to As-treated plants. Interestingly, bacterial colonization results in 40% increased As accumulation in the root, while a reduction in As translocation from root to shoot up to 89% was observed as compared to As treated plants. In conclusion, endofungal Rhizobium species Si001 association with the host plant may improve plant health and tolerance against As stress with reduced As accumulation in the crop produce.

Physiological response of soybean leaves to uniconazole under waterlogging stress at R1 stage

Waterlogging is a major limiting factor in global crop production and seriously endangers growth and yield improvement in low-lying, rainfed regions. Soybean is an important economic crop affected by waterlogging stress. The current study investigates the effects of waterlogging stress on the leaf physiology and yield of two soybean varieties (Kenfeng 14, waterlogging-tolerant and Kenfeng 16, waterlogging-sensitive) and the mitigation effect of uniconazole (S3307) in promoting growth and productivity under waterlogging conditions. The results showed that waterlogging stress increased antioxidant enzyme activity and decreased the contents of non-enzymatic antioxidants such as AsA and GSH. Furthermore, the content of MDA and H2O2 increased significantly, indicating oxidative stress and O2-· production rate also improved, and the increase in the waterlogging-sensitive variety Kenfeng 16 was greater than that of the waterlogging-tolerant variety Kenfeng 14. Spraying S3307, however, increased the activities of antioxidants such as SOD, POD, CAT, and APX. GR, MDHAR, and DHAR increased the content of non-enzymatic antioxidants, effectively inhibited the increase of MDA, H2O2 content, and O2-· production rate, and alleviated the loss of yield factors caused by waterlogging stress. The waterlogging-tolerant variety Kenfeng 14 recovered better than the waterlogging-sensitive variety Kenfeng 16. In summary, S3307 ameliorated the effects of waterlogging stress on the physiological characteristics of soybean leaves and improved yield as a result of improved antioxidant defense mechanisms that impeded lipid peroxidation. Thus, S3307 could decelerate the damages caused by waterlogging stress to some extent.