Leaf H2O2 Research Articles

Exploring the synergistic benefits of biochar and gibberellic acid in alleviating cadmium toxicity

Cadmium (Cd) toxicity significantly threatens agricultural productivity and food safety. Developing effective strategies to enhance plant tolerance to Cd stress is essential. This study investigates the synergistic effects of biochar (BC) and gibberellic acid (GA3) on mitigating Cd toxicity in maize (Zea mays), focusing on their impact on oxidative stress markers and antioxidant enzyme activities. Soil samples were collected from the Cholistan Institute of Desert Studies (CIDS) and analyzed for trace metal ions and other properties. Biochar was produced from fruit and vegetable waste, washed, washed, deashed, and mixed with 10 ppm GA3. FH-1036 hybrid maize seeds were sterilized and planted in pots containing soil with varying Cd levels (0, 8, and 16 mg Cd/kg soil). Twelve treatments were established, including control, GA3, BC, and their combinations under different Cd stress levels. Plants were irrigated to maintain 60% field capacity and harvested at the V10 growth stage. Hydrogen peroxide (H2O2) contents and activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) were measured in roots, stems, and leaves. Statistical analysis was performed using OriginPro 2021, with ANOVA and Fisher’s LSD test used to determine significant differences. GA3 and BC treatments significantly reduced H2O2 levels in maize roots, stems and leaves under Cd stress. The combined treatment of GA3 + BC showed the most significant reduction in H2O2 levels across all plant parts, reducing root H2O2 by 50%, stem H2O2 by 55%, and leaf H2O2 by 53% under severe Cd stress (16 mg Cd/kg). SOD activity increased under non-stress conditions but decreased under Cd stress, with the highest activity observed in the combined treatment. POD activity followed a similar pattern, with GA3 + BC treatment resulting in the most significant increases under non-stress conditions and the least reductions under Cd stress. CAT activity showed substantial increases with GA3 + BC treatment, particularly under severe Cd stress, with a notable rise over the control. APX activity also exhibited enhancements with GA3 and BC treatments, especially in the combined treatment under various Cd stress levels. This study highlights the potential of combined BC and GA3 treatments in improving Cd stress tolerance in maize. Future research should focus on field trials and the long-term impacts of these treatments on crop productivity and soil health.

Exogenous putrescine application imparts salt stress-induced oxidative stress tolerance via regulating antioxidant activity, potassium uptake, and abscisic acid to gibberellin ratio in Zinnia flowers

This research was conducted to investigate the efficacy of putrescine (PUT) treatment (0, 1, 2, and 4 mM) on improving morphophysiological and biochemical characteristics of Zinnia elegans “State Fair” flowers under salt stress (0, 50, and 100 mM NaCl). The experiment was designed in a factorial setting under completely randomized design with 4 replications. The results showed that by increasing the salt stress intensity, the stress index (SSI) increased while morphological traits such as plant height decreased. PUT treatments effectively recovered the decrease in plant height and flower quality compared to the not-treated plants. Treatment by PUT 2 mM under 50 and 100 mM salt stress levels reduced the SSI by 28 and 35%, respectively, and increased plant height by 20 and 27% compared to untreated plants (PUT 0 mM). 2 mM PUT treatment also had the greatest effect on increasing fresh and dry biomass, number and surface area of leaves, flower diameter, internodal length, leaf relative water content, protein contents, total chlorophyll contents, carotenoids, leaf potassium (K+) content, and K+/Na+ ratio in treated plants compared to untreated control plants. The treatment of 2 mM PUT decreased the electrolyte leakage, leaf sodium (Na+) content, H2O2, malondialdehyde, and proline content. Furthermore, PUT treatments increased the activity of defense-related enzymes including catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and phenylalanine ammonium lyase (PAL), and reduced the abscisic acid (ABA) content while increased the level of gibberellin (GA) content compared to untreated samples under all different levels of salinity stress. In this research, enhancing the plant’s antioxidant system, increasing K+ absorption, K+/Na+ ratio, and reducing the ABA/GA ratio are likely the most important mechanisms of PUT treatment, which improved growth, and maintained the visual quality of zinnia flowers under salt stress conditions.

Unravelling soybean responses to early and late Tetranychus urticae (Acari: Tetranychidae) infestation

Abstract Soybean is a crucial source of food, protein, and oil worldwide that is facing challenges from biotic stresses. Infestation of Tetranychus urticae Koch (Acari: Tetranychidae) stands out as detrimentally affecting plant growth and grain production. Understanding soybean responses to T. urticae infestation is pivotal for unravelling the dynamics of mite–plant interactions. We evaluated the physiological and molecular responses of soybean plants to mite infestation after 5 and 21 days. We employed visual/microscopy observations of leaf damage, H2O2 accumulation, and lipid peroxidation. Additionally, the impact of mite infestation on shoot length/dry weight, chlorophyll concentration, and development stages was analysed. Proteomic analysis identified differentially abundant proteins (DAPs) after early (5 days) and late (21 days) infestation. Furthermore, GO, KEGG, and protein–protein interaction analyses were performed to understand effects on metabolic pathways. Throughout the analysed period, symptoms of leaf damage, H2O2 accumulation, and lipid peroxidation consistently increased. Mite infestation reduced shoot length/dry weight, chlorophyll concentration, and development stage duration. Proteomics revealed 185 and 266 DAPs after early and late mite infestation, respectively, indicating a complex remodelling of metabolic pathways. Photorespiration, chlorophyll synthesis, amino acid metabolism, and Krebs cycle/energy production were impacted after both early and late infestation. Additionally, specific metabolic pathways were modified only after early or late infestation. This study underscores the detrimental effects of mite infestation on soybean physiology and metabolism. DAPs offer potential in breeding programs for enhanced resistance. Overall, this research highlights the complex nature of soybean response to mite infestation, providing insights for intervention and breeding strategies.

Resilient mechanism of strigolactone (GR24) in regulating morphological and biochemical status of maize under salt stress

Strigolactones (SLs), relatively recent plant growth regulators, bolster plant resilience in challenging environmental conditions and augment signaling networks. Salinity, a well-established abiotic stressor, threatens global crop cultivation and productivity. We hypothesized that the synthetic SL analogue GR24 could alleviate salinity stress in maize by reducing oxidative damage and enhancing various growth and physiological attributes. To explore this hypothesis, we subjected two maize hybrids, PB-ProA-2018 and PB-ProA-2019, to seed priming with three GR24 concentrations (non-soaked, water-soaked, 0.001, 0.01, 0.1 mg/L) for 16 h. Seeds were then germinated in sand culture under two salt stress levels [ 0 (Control) and 100 mM NaCl] and nourished with Hoagland's nutrient medium. Salt stress significantly stunted maize growth attributes. The pre-soaking seed treatment with 0.01 mg L⁻1 GR24 demonstrated a significant enhancement in plant growth metrics, yielding a 31.3% increase in root length and a 62% augmentation in total leaf area per plant, in comparison to non-soaked yet stressed plants. Salt stress led to increased activities of catalase and peroxidase, along with higher levels of leaf ascorbic acid, malondialdehyde, H₂O₂, glycine betaine, and free proline, compared to control seedlings. Pre-soaking with 0.01 mg L−1 GR24 further upregulated superoxide dismutase (SOD) by 29.6%, peroxidase (POD) by 68.3%, catalase (CAT) by 25%, ascorbic acid by 23.1%, free proline by 42.3%, and total phenolics content by 13%, compared to stressed counterparts. Notably, the 0.01 mg L−1 GR24 concentration exhibited superior efficacy in mitigating salt stress effects, with PB-ProA-2019 outperforming PB-ProA-2018 among the maize hybrids. These findings advance our understanding of SLs' potential in alleviating salinity stress in maize, offering valuable insights for crop resilience enhancement.

Application of Trichoderma asperellum spore powder helps maintain ionic balance and photosystem II activity in wolfberry in saline soil

The mechanisms how Trichoderma enhances plant salt tolerance remain to be further dissected. Trichoderma asperellum spore powder (TS) was supplemented to saline soil around the stem base of potted wolfberry (Lycium chinense), and the role of Trichoderma asperellum in ameliorating salt tolerance of wolfberry was investigated with emphasis on ionic balance and photosystems II (PSII) activity. Plant dry weight was significantly increased by TS supplement, suggesting that Trichoderma asperellum promoted wolfberry growth in saline soil. As TS supplement elevated leaf and root K+/Na+ by increasing K+ content and decreasing Na+ content, Trichoderma asperellum improved ionic balance in wolfberry under saline soil stress, and the mechanism depended on that Trichoderma asperellum raised root Na+ exclusion and blocked root K+ loss. Consequentially, oxidative stress was ameliorated by Trichoderma asperellum according to lower leaf lipid peroxidation and H2O2 content in plants with TS supplement. Moreover, PSII was protected against oxidative injury and could maintain higher photochemical efficacy with TS supplement. K and J steps in prompt chlorophyll fluorescence transients were lowered by TS supplement, suggesting that Trichoderma asperellum alleviated salt-induced inhibition on electron transport at both PSII donor and acceptor sides, and consistently, more PSII centers became reactive. In addition, higher delayed chlorophyll fluorescence transients under TS supplement corroborated that Trichoderma asperellum enhanced whole PSII performance. Overall, Trichoderma asperellum helped maintain ionic balance by preventing K+ loss and elevating Na+ exclusion in roots and protect PSII by alleviating oxidative stress in wolfberry cultivated in saline soil.

Sodium nitroprusside as a signal molecule for up-regulating membrane characteristics, antioxidant defense system to improve flax productivity under water stress

Water stress is a critical environmental adversity that significantly impacts the growth, development, and yield of flax plants. In this study, flax seeds were cultivated under different water irrigation requirements (WIR) (100%, 75%, and 50%) to investigate the effects of exogenously supplied nitric oxide (NO) donor sodium nitroprusside (SNP) as foliar treatments at concentrations of 0.0 ​mmol/L, 0.5 ​mmol/L, 1.0 ​mmol/L, and 2.0 ​mmol/L. Drought stress led to a significant decrease in plant growth, photosynthetic pigments, yield components such as oil and total carbohydrate percentage. It also resulted in an increase in leaf H2O2 production, lipid peroxidation levels and activities of enzymatic antioxidants including polyphenol oxidase, superoxide dismutase, and nitrate reductase enzymes. However, foliar application of SNP improved photosynthetic pigments and antioxidant defense system which mitigated the negative impact of water stress on growth and yield productivity by reducing oxidative damage caused by reactive oxygen species accumulation. The use of SNP also decreased H2O2 accumulation levels, lipid peroxidation levels, and improved membrane stability. SNP treatment at concentration of 2 ​mmol/L showed superior results compared to other concentrations with extremely significant increases observed in yield characteristics such as oil content, total carbohydrate percentages, and unsaturated fatty acids to saturated fatty acids ratio.

Contribution of Antioxidant System Components to the Long-Term Physiological and Protective Effect of Salicylic Acid on Wheat under Salinity Conditions.

Salicylic acid (SA) plays a crucial role in regulating plant growth and development and mitigating the negative effects of various stresses, including salinity. In this study, the effect of 50 μM SA on the physiological and biochemical parameters of wheat plants under normal and stress conditions was investigated. The results showed that on the 28th day of the growing season, SA pretreatment continued to stimulate the growth of wheat plants. This was evident through an increase in shoot length and leaf area, with the regulation of leaf blade width playing a significant role in this effect. Additionally, SA improved photosynthesis by increasing the content of chlorophyll a (Chl a) and carotenoids (Car), resulting in an increased TAP (total amount of pigments) index in the leaves. Furthermore, SA treatment led to a balanced increase in the levels of reduced glutathione (GSH) and oxidized glutathione (GSSG) in the leaves, accompanied by a slight but significant accumulation of ascorbic acid (ASA), hydrogen peroxide (H2O2), proline, and the activation of glutathione reductase (GR) and ascorbate peroxidase (APX). Exposure to salt stress for 28 days resulted in a reduction in length and leaf area, photosynthetic pigments, and GSH and ASA content in wheat leaves. It also led to the accumulation of H2O2 and proline and significant activation of GR and APX. However, SA pretreatment exhibited a long-term growth-stimulating and protective effect under stress conditions. It significantly mitigated the negative impacts of salinity on leaf area, photosynthetic pigments, proline accumulation, lipid peroxidation, and H2O2. Furthermore, SA reduced the salinity-induced depletion of GSH and ASA levels, which was associated with the modulation of GR and APX activities. In small-scale field experiments conducted under natural growing conditions, pre-sowing seed treatment with 50 μM SA improved the main indicators of grain yield and increased the content of essential amino acids in wheat grains. Thus, SA pretreatment can be considered an effective approach for providing prolonged protection to wheat plants under salinity and improving grain yield and quality.

Peroxidase gene TaPrx109-B1 enhances wheat tolerance to water deficit via modulating stomatal density.

Increasing the tolerance of crops to water deficit is crucial for the improvement of crop production in water-restricted regions. Here, a wheat peroxidase gene (TaPrx109-B1) belonging to the class III peroxidase gene family was identified and its function in water deficit tolerance was revealed. We demonstrated that overexpression of TaPrx109-B1 reduced leaf H2O2 level and stomatal density, increased leaf relative water content, water use efficiency, and tolerance to water deficit. The expression of TaEPF1 and TaEPF2, two key negative regulators of stomatal development, were significantly upregulated in TaPrx109-B1 overexpression lines. Furthermore, exogenous H2O2 downregulated the expression of TaEPF1 and TaEPF2 and increased stomatal density, while exogenous application of diphenyleneiodonium chloride, a potent NADPH oxidase inhibitor that repressed the synthesis of H2O2, upregulated the expression of TaEPF1 and TaEPF2, decreased stomatal density, and enhanced wheat tolerance to water deficit. These findings suggest that TaPrx109-B1 influences leaf stomatal density by modulation of H2O2 level and the expression of TaEPF1 and TaEPF2. The results of the field trial showed that overexpressing TaPrx109-B1 increased grain number per spike, which reduced the yield loss caused by water deficiency. Therefore, TaPrx109-B1 has great potential in breeding wheat varieties with improved water deficit tolerance.

Heat-Resistant Inbred Lines Coordinate the Heat Response Gene Expression Remarkably in Maize (Zea mays L.).

High temperatures are increasingly becoming a prominent environmental factor accelerating the adverse influence on the growth and development of maize (Zea mays L.). Therefore, it is critical to identify the key genes and pathways related to heat stress (HS) tolerance in maize. Great challenges have been faced in dissecting genetic mechanisms and uncovering master genes for HS tolerance. Here, Z58D showed more thermotolerance than AF171 at the seedling stage with a lower wilted leaf rate and H2O2 accumulation under HS conditions. Transcriptomic analysis identified 3006 differentially expressed genes (DEGs) in AF171 and 4273 DEGs in Z58D under HS treatments, respectively. Subsequently, GO enrichment analysis showed that commonly upregulated genes in AF171 and Z58D were significantly enriched in the following biological processes, including protein folding, response to heat, response to temperature stimulus and response to hydrogen peroxide. Moreover, the comparison between the two inbred lines under HS showed that response to heat and response to temperature stimulus were significantly over-represented for the 1234 upregulated genes in Z58D. Furthermore, more commonly upregulated genes exhibited higher expression levels in Z58D than AF171. In addition, maize inbred CIMBL55 was verified to be more tolerant than B73, and more commonly upregulated genes also showed higher expression levels in CIMBL55 than B73 under HS. These consistent results indicate that heat-resistant inbred lines may coordinate the remarkable expression of genes in order to recover from HS. Additionally, 35 DEGs were conserved among five inbred lines via comparative transcriptomic analysis. Most of them were more pronounced in Z58D than AF171 at the expression levels. These candidate genes may confer thermotolerance in maize.

Improvement in physio-biochemical characteristics of shallot plants with nano silica at several levels of drought stress

Plants are stressed if the environment in which they grow changes, which can reduce the rate of vegetative and generative growth and finally the production of plant. One of the factors that causes stress in plants is the availability of water which greatly influences the productivity of shallot plants as shown by changes in physiological and biochemical characters. Analysis of physiobiochemical characteristics of shallots for the application of nano silica at several levels of water stress is the aim of this research. Parameters analyzed at the Central Pharmacy Research Laboratory Faculty of Pharmacy, Tissue Culture Laboratory and Disease Laboratory, Faculty of Agriculture, Universitas Sumatera Utara, November 2022 to March 2023. This study used RBCD with 2 treatment factors. The first factor namely water stress condition (80, 60 and 40% field capacity). The second factor namely the application of nano silica which consisted of 4 levels of concentration (0, 6, 12 and 18 g/l). The results showed that the addition of water based on field capacity at 80% optimal conditions significantly increasing chlorophyll a, b, and total, leaf relative water content, H2O2 and SOD enzymes. Application of nanosilica at concentration of 18 g/l significantly increased chlorophyll a, b and total.

H2O2 leaf priming improves tolerance to cold stress in pistachio rootstocks

H2O2 leaf priming improves tolerance to cold stress in pistachio rootstocks

Physiological and Biochemical Mechanisms of Wood Vinegar-Induced Stress Response against Tomato Fusarium Wilt Disease.

Wood vinegar, a by-product of charcoal biomass pyrolysis, has been used as a biofungicide in plant disease management because of its antimicrobial properties. However, the physiological and biochemical mechanisms through which wood vinegar alleviates biotic stress are poorly understood. In this study, pot experiments were conducted to investigate the resistance and regulation mechanism of wood vinegar prepared from different raw materials (ZM) and from a single raw material (SM) in controlling tomato (Solanum lycopersicum "Bonny Best") Fusarium wilt at different concentrations (0.3%, 0.6%, 0.9%, 1.2%, and 1.5%). The results showed that ZM and SM had significant control effects on tomato fusarium wilt under different concentrations in the same growth cycle. Under biotic stress, the two kinds of wood vinegar significantly increased the plant height, stem diameter, leaf area and yield of tomato under the concentration of 0.3%, 0.6%, 0.9% and 1.2%, and significantly reduced the content of malondialdehyde (MDA) and hydrogen peroxide (H2O2) in tomato leaves. The effect of 0.9% treatment was the most significant, ZM and SM significantly increased tomato yield by 122% and 74%, respectively, compared with CK under 0.9% treatment. However, the plant height, stem diameter and leaf area of tomato were significantly reduced under 1.5% treatment, but the content of soluble sugar, soluble protein and vitamin C in tomato fruit was the best. Compared with CK, ZM significantly increased by 14%, 193% and 67%, respectively, and SM significantly increased by 28%, 300% and 159%, respectively. Except for 0.3% treatment, both significantly increased the activities of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) in tomato leaves. The response intensity of two kinds of wood vinegar-physiological and biochemical-to tomato disease resistance, growth and development, showed ZM > SM. The disease index of tomato showed highly significant negative correlation with plant height, stem thickness, leaf area and antioxidant physiology CAT, and highly significant positive correlation with MDA and H2O2 content. In conclusion, ZM was more effective than SM in enhancing tomato disease resistance by promoting tomato growth and development, decreasing leaf MDA and H2O2 content, and inducing antioxidant enzyme activity in leaves at moderate concentrations.

Enhancement of soybean tolerance to water stress through regulation of nitrogen and antioxidant defence mechanisms mediated by the synergistic role of salicylic acid and thiourea

Water stress (WS) poses a significant threat to global food and energy security by adversely affecting soybean growth and nitrogen metabolism. This study explores the synergistic effects of exogenous salicylic acid (SA, 0.5 mM) and thiourea (TU, 400 mg L−1), potent plant growth regulators, on soybean responses under WS conditions. The treatments involved foliar spraying for 3 days before inducing WS by reducing soil moisture to 50% of field capacity, followed by 2 weeks of cultivation under normal or WS conditions. WS significantly reduced plant biomass, chlorophyll content, photosynthetic efficiency, water status, protein content, and total nitrogen content in roots and leaves. Concurrently, it elevated levels of leaf malondialdehyde, H2O2, proline, nitrate, and ammonium. WS also triggered an increase in antioxidant enzyme activity and osmolyte accumulation in soybean plants. Application of SA and TU enhanced the activities of key enzymes crucial for nitrogen assimilation and amino acid synthesis. Moreover, SA and TU improved plant growth, water status, chlorophyll content, photosynthetic efficiency, protein content, and total nitrogen content, while reducing oxidative stress and leaf proline levels. Indeed, the simultaneous application of SA and TU demonstrated a heightened impact compared to their separate use, suggesting a synergistic interaction. This study underscores the potential of SA and TU to enhance WS tolerance in soybean plants by modulating nitrogen metabolism and mitigating oxidative damage. These findings hold significant promise for improving crop productivity and quality in the face of escalating water limitations due to climate change.

Effects of foliar applications of a proline-rich specific yeast derivative on physiological and productive performances of field-grown grapevines (Vitis vinifera L.)

The occurrence of heat waves in vineyards can damage the integrity of photosynthetic systems, impair yield and affect fruit quality. The frequency of these events is increasing due to global warming, and this is the subject of growing concern among the players in the wine sector. Canopy applications of specific yeast derivatives (SYD) are proposed to enhance plant physiology under abiotic stresses and preserve yield and fruit composition. This study aimed at assessing the effects of foliar application of a proline-rich SYD formulate, LalVigne ProHydro™ (LPH), on field-grown vines cv. Barbera. In a two-year experiment, vines subjected to multiple LPH foliar applications were compared to untreated vines (C). Gas exchange rates and vegetative and productive performances were monitored together with leaf proline, carotenoids and H2O2 concentrations. The data demonstrate that the formulate improved midday leaf water potential (+0.14 MPa), stomatal conductance (+0.15 mol m−2 s−1) and assimilation rates (+2.8 μmol m−2 s−1) under summer stress conditions. Interestingly, LPH leaves showed a dramatically higher concentration of proline (+600 %) and a significantly lower H2O2 content (-26 %) as compared to C leaves. The data suggest that this could be related to a priming effect of LPH application. Moreover, in SYD vines, cluster sunburn occurrence was reduced by 69 %, compared to C vines. At harvest, LPH improved vine yield (+1.27 kg), and LPH grapes had a significantly lower sugar concentration (-2.09 °Brix). The study demonstrates for the first time the potential benefits of proline-rich SYD application in vineyards subjected to multiple summer stress. Further studies should focus on the treatment effects on proline biosynthesis and gene expression.

Transcriptome analysis of resistant and susceptible grapes reveals molecular mechanisms underlying resistance of white rot disease

Grape production in China is significantly impacted by white rot disease, which is caused by Coniella diplodiella (Speg.) Sacc. This study analyzes the differences in leaf transcriptomes and phenotypes of two grape species, ‘Manicure Finger (Vitis vinifera L.)’ and ‘0940 (Vitis davidii Foex)’, following inoculation with C. diplodiella. Leaf anatomy and H2O2 content confirm the greater resistance of '0940' to C. diplodiella compared to 'Manicure Finger.' Comparative transcriptome analysis reveals that the defense mechanism of '0940' against C. diplodiella involves sesquiterpenoid and triterpenoid biosynthesis, plant-pathogen interactions, sulfur relay systems, suberin and wax biosynthesis, monoterpenoid biosynthesis, as well as flavonoid and flavonol biosynthesis pathways. Using Weighted Gene Co-expression Network Analysis (WGCNA), we identified three modules highly correlated with C. diplodiella resistance and 125 candidate genes, including resistant genes (R genes), pattern-recognition receptors (PRRs), and pathogenesis-related proteins genes (PR genes), which may play important roles in grape resistance to this disease.

Hub Gene Identification and Heat-Stress-Related Transcriptional Regulation Mechanism in Cabbage (Brassica oleracea L.)

Cabbage is a heat-stress-sensitive cool-season crop. When exposed to high temperatures, cabbage plants can experience reduced growth, wilting, leaf yellowing, and premature bolting (the formation of a flowering stem). The regulatory mechanism controlling heat stress is poorly understood in cabbage. To investigate this mechanism, physiological changes and transcriptional profiling for different heat treatment times were analyzed in this study. The results showed that superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities were enhanced under heat stress. In particular, the increase in SOD and POD activities after 12 h of heat treatment was greater than that after 4 h of heat treatment. With increasing heat treatment duration, the leaf CAT activity and H2O2 content decreased after the initial increase. The electrolyte leakage and malondialdehyde (MDA) content dropped significantly, while the proline content increased. Alongside that, 7007 and 5537 upregulated genes were identified in the experimental group treated with heat stress for the 4 h and 12 h treatments, respectively. We found that 10,479 DEGs were shared in the heat stress treatment, of which 1241 were associated with the heat treatment time. By integrating the expression patterns and functional annotations of genes related to heat stress, we identified 15 hub genes that respond to heat stress in cabbage. Meanwhile, we had constructed a physiological to molecular model of cabbage response to long-term heat stress. These findings provide new insights for the comprehensive analysis of cabbage response to heat stress and genetic resources for breeding new varieties of cabbage with heat tolerance via genetic engineering.

Evaluation of heat stress induced plant metabolites in Fagopyrum esculentum Moench. by exogenous application of plant growth promoters

Global warming has a direct relation with high temperature and management of heat stress in field crops is important for sustainable agriculture. Common buckwheat ( Fagorpyrum esculentum Moench.) is an emerging pseudocereal and alternative food crop but shows sensitivity to heat stress. This two years (2017 and 2018) research was conducted to explore the physiological and biochemical mechanism of improving heat stress tolerance in buckwheat with foliar spray of different plant growth promoters (PGPs). The preoptimized levels of moringa leaf extract (MLE) of fresh (MFLE, 3%) and dried leaves (MDLE, 10%), ascorbic acid (AsA, 0.5 mM), a vitamin biosynthesized in plants and thiourea (TU, 10 mM), a synthetic growth bioregulator were foliar sprayed. Results revealed that growth attributes including shoot (34.61%) and root length (27.62%), dry weight (641.94% and 40.23%, respectively), stem diameter (52.05%), no. of roots per plant (27.27%), leaf area (24.86%), and no. of internodes per plant (16.17%) were impaired by heat stress. Similarly, antioxidants including leaf and root superoxide dismutase (17.11% and 21.43%), peroxidase (16.81% and 8.40%) and catalase (6.51% and 6.54%), respectively, were significantly affected by heat stress. PGPs spray alleviated heat damage by reducing the biosynthesis of leaf and root MDA and H2O2, and preferential induction of enzymatic antioxidants. PCA-biplot analysis showed that, amongst PGPs, MDLE was greatly effective in inducing antioxidant defense under heat stress. PCA and correlation matrix revealed that PGPs prompted induction of antioxidants was effective more in roots than leaves under heat stress. Conclusively, the induction of antioxidant defense with the PGPs especially with MLEs spray is the main mechanism, with great implications for heat tolerance in common buckwheat.

Foliar Application of Chelated Sugar Alcohol Calcium Improves Photosynthesis and Tuber Quality under Drought Stress in Potatoes (Solanum tuberosum L.).

Drought stress is a major threat to sustainable crop production worldwide. Despite the positive role of calcium (Ca2+) in improving plant drought tolerance in different crops, little attention has been paid to its role in mitigating drought stress in potatoes. In the present study, we studied the effect of foliar chelated sugar alcohol calcium treatments on two potato cultivars with different drought responses applied 15 and 30 days after limiting soil moisture. The results showed that the foliar application of calcium treatments alleviated the SPAD chlorophyll loss of the drought-sensitive cultivar 'Atlantic' (Atl) and reduced the inhibition of photosynthetic parameters, leaf anatomy deformation, and MDA and H2O2 content of both cultivars under drought stress. The Ca2+ treatments changed the expression of several Calcium-Dependent Protein Kinase (StCDPK) genes involved in calcium sensing and signaling and significantly increased antioxidant enzyme activities, average tuber weight per plant, and tuber quality of both cultivars. We conclude that calcium spray treatments improved the drought tolerance of both potato cultivars and were especially effective for the drought-sensitive cultivar. The present work suggests that the foliar application of calcium is a promising strategy to improve commercial potato yields and the economic efficiency of potato production under drought stress conditions.

Antioxidant and drought-acclimation responses in UV-B-exposed transgenic Nicotiana tabacum displaying constitutive overproduction of H2O2.

Hydrogen peroxide (H2O2) is an important molecule that regulates antioxidant responses that are crucial for plant stress resistance. Exposure to low levels of ultraviolet-B radiation (UV-B, 280-315nm) can also activate antioxidant defenses and acclimation responses. However, how H2O2 and UV-B interact to promote stress acclimation remains poorly understood. In this work, a transgenic model of Nicotiana tabacum cv Xanthi nc, with elevated Mn-superoxide dismutase (Mn-SOD) activity, was used to study the interaction between the constitutive overproduction of H2O2 and a 14-day UV-B treatment (1.75kJm-2 d-1 biologically effective UV-B). Subsequently, these plants were subjected to a 7-day moderate drought treatment to evaluate the impact on drought resistance of H2O2- and UV-dependent stimulation of the plants' antioxidant system. The UV-B treatment enhanced H2O2 levels and altered the antioxidant status by increasing the epidermal flavonol index, Trolox Equivalent Antioxidant Capacity, and catalase, peroxidase and phenylalanine ammonia lyase activities in the leaves. UV-B also retarded growth and suppressed acclimation responses in highly H2O2-overproducing transgenic plants. Plants not exposed to UV-B had a higher drought resistance in the form of higher relative water content of leaves. Our data associate the interaction between Mn-SOD transgene overexpression and the UV-B treatment with a stress response. Finally, we propose a hormetic biphasic drought resistance response curve as a function of leaf H2O2 content in N. tabacum cv Xanthi.

Exogenous application of selenium and nano-selenium alleviates salt stress and improves secondary metabolites in lemon verbena under salinity stress

Salinity stress is one of the most serious abiotic factors that affects the growth, performance, and secondary compounds of medicinal plants. The aim of this study was to determine the effect of foliar application of selenium and nano-selenium separately on growth, essential oils, physiological parameters, and some secondary metabolites of Lemon verbena under salinity stress. The results showed that selenium and nano-selenium significantly increased growth parameters, photosynthetic pigments, and relative water content. Compared to the control, a higher accumulation of osmolytes (i.e., proline, soluble sugars, and total protein) and higher antioxidant activity were observed in the selenium-treated plants. In addition, selenium alleviated the adversary effect of oxidative stress, resulting from salinity, by reducing leaf electrolyte leakage, malondialdehyde, and H2O2 accumulation. Furthermore, selenium and nano-selenium enhanced the biosynthesis of secondary metabolites such as essential oils, total phenolic content, and flavonoid compounds under non-stress and salinity conditions. They also reduced Na+ accumulation in the root and shoot of the salinity-treated plants. Hence it can be concluded that exogenous application of selenium and nano-selenium separately can mitigate the negative effects of salinity by improving the quantitative and qualitative performance of lemon verbena plants under salinity stress.