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Melatonin (Mel) and hydrogen sulphide (H2 S) have emerged as potential regulators of plant metabolism during abiotic stress. Presence of excess NaCl in the soil is one of the main causes of reduced crop productivity worldwide. The present investigation examines the role of exogenous Mel and endogenous H2 S in tomato seedlings grown under NaCl stress. Effect of 30 µm Mel on endogenous synthesis of H2 S was examined in roots of NaCl-stressed (200 mm) tomato seedlings. Also, the impact of treatments on the oxidative stress markers, transport of K+ and Na+ , and activity of H+ -ATPase and antioxidant enzymes was assessed. Results show that NaCl-stressed seedlings supplemented with 30 µm Mel had increased levels of endogenous H2 S through enhanced L-cysteine desulfhydrase activity. Mel in association with H2 S overcame the deleterious effect of NaCl and induced retention of K+ that maintained a higher K+ /Na+ ratio. Use of plasma membrane inhibitors and an H2 S scavenger revealed that Mel-induced regulation of K+ /Na+ homeostasis in NaCl-stressed seedling roots operates through endogenous H2 S signalling. Synergistic effects of Mel and H2 S also reduced the generation of ROS and oxidative destruction through the enhanced activity of antioxidant enzymes. Thus, it is suggested that the protective function of Mel against NaCl stress operates through an endogenous H2 S-dependent pathway, wherein H+ -ATPase-energized secondary active transport regulates K+ /Na+ homeostasis.

Copper (Cu) contamination in soils is becoming a serious problem. Therefore, an experiment in plastic pots was carried out to investigate interactive influence of rice straw BC (BC0:0, BC1:5, and B...

Exogenous potassium (K + ) and endogenous hydrogen sulfide (H 2 S) synergistically alleviate drought stress through regulating H + -ATPase activity, sugar metabolism and redox homoeostasis in tomato seedlings . Present work evaluates the role of K+ in the regulation of endogenous H2S signaling in modulating the tolerance of tomato (Solanum lycopersicum L. Mill.) seedlings to drought stress. The findings reveal that exposure of seedlings to 15% (w/v) polyethylene glycol 8000 (PEG) led to a substantial decrease in leaf K+ content which was associated with reduced H+-ATPase activity. Treatment with sodium orthovanadate (SOV, PM H+-ATPase inhibitor) and tetraethylammonium chloride (TEA, K+ channel blocker) suggests that exogenous K+ stimulated H+-ATPase activity that further regulated endogenous K+ content in tomato seedlings subjected to drought stress. Moreover, reduction in H+-ATPase activity by hypotaurine (HT; H2S scavenger) substantiates the role of endogenous H2S in the regulation of H+-ATPase activity. Elevation in endogenous K+ content enhanced the biosynthesis of H2S through enhancing the synthesis of cysteine, the H2S precursor. Synergistic action of H2S and K+ effectively neutralized drought stress by regulating sugar metabolism and redox homoeostasis that resulted in osmotic adjustment, as witnessed by reduced water loss, and improved hydration level of the stressed seedlings. The integrative role of endogenous H2S in K+ homeostasis was validated using HT and TEA which weakened the protection against drought stress induced impairments. In conclusion, exogenous K+ and endogenous H2S regulate H+-ATPase activity which plays a decisive role in the maintenance of endogenous K+ homeostasis. Thus, present work reveals that K+ and H2S crosstalk is essential for modulation of drought stress tolerance in tomato seedlings.

Bacterial spot, caused by a group of Xanthomonads (Xanthomonas spp.), is a devastating disease. It can adversely affect the Capsicum annum productivity. Scientists are working on the role of antioxidants to meet this challenge. However, research is lacking on the role of antioxidant enzymes and their isoforms in the non-compatible pathogen and host plant interaction and resistance mechanisms in capsicum varieties. The present study was conducted to ascertain the defensive role of antioxidant enzymes and their isoforms in chilli varieties Hybrid, Desi, Serrano, Padron, and Shehzadi against bacterial spot disease-induced Xanthomonas sp. The seedlings were inoculated with bacterial pathogen @ 107 CFU/mL, and samples were harvested after regular intervals of 24 h for 4 days followed by inoculation. Total plant proteins were extracted in phosphate buffer and quantified through Bradford assay. The crude protein extracts were analyzed through quantitative enzymatic assays in order to document activity levels of various antioxidant enzymes, including peroxidase (POD), Catalase (CAT), Ascorbate peroxidase (APX), and Superoxide dismutase (SOD). Moreover, the profiles appearance of these enzymes and their isoforms were determined using native polyacrylamide gel electrophoresis (PAGE) analysis. These enzymes exhibited maximum activity in Hybrid (HiR) cultivar followed by Desi (R), Serrano (S), Padron, and Shehzadi (HS). Both the number of isoforms and expression levels were higher in highly resistant cultivars compared to susceptible and highly susceptible cultivars. The induction of POD, CAT, and SOD occurs at the early stages of growth in resistant Capsicum cultivars. At the same time, APX seems to make the second line of antioxidant defense mechanisms. We found that modulating antioxidant enzymes and isoforms activity at the seedling stage was an important mechanism for mitigating plant growth inhibition in the resistant ones.

Inadequate plant stand establishment due to insufficient germination is an important bottleneck in achieving the potential yields, specifically under uncertain growing conditions. Hydropriming has been publicized as a useful tool to alleviate the stress-induced consequences. Association of DNA biosynthesis in hydroprimed seeds of maize; hybrid, PEHM 5 and its parental lines (CM150 and CM151) was studied. Seeds were hydroprimed at 25 °C for 30 h and half of them were surface dried while the other half were redried back to the original moisture contents. The treated and untreated seeds were evaluated for; germination test, mean germination time, vigour index and DNA levels in embryos of fully matured seeds. Both the treatment strategies significantly enhanced the planting value of maize seeds. Vigour index I revealed significant correlation with G2/G1 ratio whereas significant negative correlation between G2/G1 ratio and mean germination time was observed. Large amounts of 2C DNA signals in flow cytometric analysis divulged that most cells might had arrested in the cell cycle at the pre synthetic G1 phase of nuclear division. Augmentation of 4C signal in the embryonic region was noticed after imbibition that could be ascribed to cells entering the synthetic phase of nuclear division. The embryonic cells showed increased 4C:2C ratios after 30 h of imbibition. Apparently, DNA synthesis preceded germination. In dry seeds, DNA histograms revealed both a 2C signal and a considerable 4C peak. A priming period of 30 h in distilled water considerably enhanced the rate and uniformity of germination in both surface dried and redried treatment strategies. Upon priming, the ratio of 4C:2C increased during the 30 h priming period, though the level in case of redried seeds did not reach the level obtained after hydration in water without drying back. However, the 4C: 2C ratio was constant after redrying the seeds to the original moisture content, indicating that the chromosomal material in the embryonic cells had stably ceased cell cycle activity at the G2 phase. The present results indicate that the beneficial effects of priming on seedling performance could be associated with the action of replicative DNA synthesis processes prior to germination.

The interaction of mineral nutrients with metals/metalloids and signalling molecules is well known. In the present study, we investigated the effect of phosphorus (P) in mitigation of arsenic (As) stress in mustard (Brassica juncea L.). The study was conducted to investigate potential of 30 mg P·kg-1 soil P supplement (diammonium phosphate) to cope up with the adverse effects of As stress (24 mg As·kg-1 soil) in mustard plants Supplementation of P influenced nitric oxide (NO) generation, which up-regulated proline metabolism, ascorbate-glutathione system and glyoxalase system and alleviated the effects of on photosynthesis and growth. Arsenic stress generated ROS and methylglyoxal content was scavenged through P-mediated NO, and reduced As translocation from roots to leaves. The involvement of NO under P-mediated alleviation of As stress was substantiated with the use of cPTIO (NO biosynthesis inhibitor) and SNP (NO inducer). The reversal of P effects on photosynthesis under As stress with the use of cPTIO emphasized the role of P-mediated NO in mitigation of As stress and protection of photosynthesis The results suggested that P reversed As-induced oxidative stress by modulation of NO formation, which regulated antioxidant machinery. Thus, P-induced regulatory interaction between NO and reversal of As-induced oxidative stress for the protection of photosynthesis may be suggested for sustainable crops.

Soil salinity and drought stress (DS) are the massive problem for worldwide agriculture. Both stresses together become more toxic to the plant growth and development. Silicon (Si) being the second most abundant element in the earth's crust, exerts beneficial effects on plants under both stress and non-stress conditions. However, limited information is available to substantiate the beneficial role of Si in delaying the premature leaf senescence and imparting tolerance of mustard (Brassica juncea L.) plants to salinity and DS. Therefore, the present study aimed to explore the role of Si (source K2SiO3) in chlorophyll (Chl) biosynthesis, nutrients uptake, relative water content (RWC), proline (Pro) metabolism, antioxidant system and delaying of premature leaf senescence in mustard plants under sodium chloride (NaCl) and DS conditions. Results of this study show that exogenous Si (1.7 mM) significantly delayed the salt plus DS-induced premature leaf senescence. This was further accompanied by the enhanced nutrients accumulation and activity of chlorophyll metabolizing enzymes [δ-aminolevulinic acid (δ-ALA) dehydratase and porphobilinogen deaminase] and levels of δ-ALA, and Chls a and b and also by decreased the Chl degradation and Chl degrading enzymes (Chlorophyllase, Chl-degrading peroxidase, pheophytinase) activity. Exogenous Si treatment induced redox homoeostasis in B. juncea L. plants, which is evident by a reduced generation of reactive oxygen species (ROS) resulting due to suppressed activity of their generating enzymes (glycolate oxidase and NADPH oxidase) and enhanced defence system. Furthermore, application of Si inhibited the activity of protease and triggered the activity of antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase) and plasma membrane H+-ATPase activity. In conclusion, all these results reveal that Si could help in the modulation of Chl metabolism, redox hemostasis, and the regulation of nutrients (nitrogen, phosphorus, Si and potassium) uptake in the mustard plants that lead to the postponement of premature leaf senescence under salinity plus DS.

At present plants continuously exposed to salinity stress due to the challenging environment that has reduced the crop growth and productivity worldwide. Application of phytohormones by using seed priming method emerges as one of the most reliable and cost effective to alleviate the toxic effect of salinity stress. In this study, we evaluate the effect of seed-primed salicylic acid (SA) to reduce the adverse effect of different salt concentrations (0, 100, 200, and 300 mM NaCl) in pea (Pisum sativum L.) seedlings. After seedling emergence, percent seed germination was calculated; however, after 60 days; plants were sampled for studying the growth and photosynthetic traits, lipid peroxidation level, antioxidant activities, ions accumulation, and its sequestration. The results depicted that salinity treatments hampered overall growth performance and induced oxidative stress in a dose-dependent manner. Salinity also has negatively influence on ion accumulation as Na+ ion increased while K+ ion decreased. On the other hand, seed priming with SA significantly reduced the salinity-induced effects on the overall performance of plants, including growth and photosynthetic attributes. SA alleviated the adverse effect of salinity even at higher salinity level by inducing enzymatic and non-enzymatic antioxidant systems, soluble sugars, and proline accumulation, and regulating ion homeostasis along with up-regulation of Na+/H+ antiporters (SOS1 and NHX1). Thus, seed priming with SA shows a comprehensive role in mitigation of salinity stress and can be used as a model for promising salinity tolerant cultivation.

Melatonin is a crucial biological hormone associated with many physiological and biochemical processes in plants and also enhances resistance against various abiotic stresses. However, the mechanisms underlying the melatonin-assisted mitigation of salt stress in tomato (Solanum lycopersicum L.) plant are still poorly understood. A hydroponic experiment was conducted to investigate the protective role of melatonin in two tomato cultivars (Roma and FM9) under a highly saline growth medium (160 mM NaCl). The one level of melatonin (1.0 µmol L−1) was applied exogenously, sole, or in combination with the salinity stress. NaCl-induced phytotoxicity significantly (P

Salinity is one of the major abiotic stresses that limit productivity of pulse crops all over the world. Seed priming with phytohormone(s) is one of the most promising, authentic and cost-effective methods to mitigate the deleterious effect of salinity. The study was conducted to investigate potential of seed priming with gibberellic acid (GA3 ) to cope up with the adverse effects of salinity (0, 100, 200 and 300 mm NaCl) in pea (Pisum sativum L.) seedlings. There were different responses to salinity, which induced oxidative stress, higher accumulation of Na+ in shoots and roots and inhibition of photosynthetic traits. However, seed priming with GA3 showed promising effects on physiological traits under salinity stress and alleviated the adverse effects of salinity by inducing the antioxidant system, proline production, total phenol and flavonoid content and regulating ion homeostasis, along with up-regulation of Na+ /H+ antiporters (SOS1 and NHX1). Plants adapt and prevent high salt accumulation by inducing expression of Na+ /H+ antiporter (SOS1 and NHX1) proteins that enhance Na+ sequestration. Thus, seed priming with GA3 is important in alleviation of high salinity stress and can be used as a criterion for developing salt-tolerant cultivars.

Strigolactone (GR24) is a phytohormone, involved in reconfiguration of plant development pattern in response to salinity stress. Current experiment was carried out in vitro conditions to study the role of GR24 on sunflower (Helianthus annuus L. cv. OLIVER-P) under saline and non-saline growth mediums. Two salinity levels [0 mM (control) and 150 mM NaCl] were maintained in growth mediums for callus induction along with four GR24 levels (0, 0.001, 0.01, 0.1 mg L−1) in Somatic Cell Genetic Lab, Centre of Agricultural Biochemistry and Biotechnology (CABB), University of Agriculture Faisalabad, Pakistan. Results of this study showed that among GR24 levels, 0.01 mg L−1 proved to be ideal dose as it improved callus fresh weight (30.59%), dry weight (45.26%), free protein (55.87%), Ca2+ (13.04%) and K+ (11.76%) contents under non-saline, while superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), free proline and glycine betaine (GB) contents by 38.1%, 67.87%, 124.01%, 63.38% and 76.12%, respectively, under salinity stress mediums. However, water potential (Ψw), osmotic potential (Ψs), turgor potential (Ψp), hydrogen peroxide (H2O2) and malondialdehyde (MDA) were reduced up to 32.65%, 39.80%, 40.74%, 65.78% and 30.76%, respectively, due to different levels of GR24. Overall, high saline conditions caused a significant reduction in concentration of callus biomass, Ψw, Ψs, soluble protein, Ca2+ and K+ ions than non-saline mediums. These results reflected that GR24 application could be an effective approach to mitigate hazardous impacts of salinity in sunflower production. Further, the molecular techniques of processes in which GR24 may play a key role in different commercially vital crops is extreme important and may carry new leads for future experimentation in this exciting area of plant hormones.

Abiotic stresses are the primary sources of crop losses globally. The identification of key mechanisms deployed and established by plants in response to abiotic stresses is necessary for the maintenance of their growth and persistence. Recent discoveries have revealed that phytohormones or plant growth regulators (PGRs), mainly jasmonic acid (JA), have increased our knowledge of hormonal signaling of plants under stressful environments. Jasmonic acid is involved in various physiological and biochemical processes associated with plant growth and development as well as plant defense mechanism against wounding by pathogen and insect attacks. Recent findings suggest that JA can mediate the effect of abiotic stresses and help plants to acclimatize under unfavorable conditions. As a vital PGR, JA contributes in many signal transduction pathways, i.e., gene network, regulatory protein, signaling intermediates and enzymes, proteins, and other molecules that act to defend cells from the harmful effects of various environmental stresses. However, JA does not work as an independent regulator, but acts in a complex signaling pathway along other PGRs. Further, JA can protect and maintain the integrity of plant cells under several stresses by up-regulating the antioxidant defense. In this review, we have documented the biosynthesis and metabolism of JA and its protective role against different abiotic stresses. Further, JA-mediated antioxidant potential and its crosstalk with other PGRs have also been discussed.

Nitric oxide (NO), a signaling molecule with diverse physiological functions, improves immunity of the plant against different environmental stresses. Heavy metal stress-induced structural and functional damages in cells are common consequences. Seed germination and seedlings development are crucial phases in the life cycle of a plant. The present experiment was designed to investigate how NO suppresses hexavalent chromium Cr(VI)-provoked impairment in the key processes during seed germination and seedlings development of tomato. This study reports that Cr(VI) stress significantly impaired seed germination attributes and the activity of hydrolyzing enzymes, such as α-amylase (α-A) and protease (Pr). However, exogenous NO donor sodium nitroprusside substantially improved seed germination parameters and upregulation of α-A and Pr. Furthermore, NO improved the content of nitrogen (N), NO, and proline (Pro), and modulated the activity of enzymes involved in Pro and N-assimilation. Under Cr(VI) toxicity conditions, NO improved the content of metal ligation compounds (non-protein thiols and total thiols), ascorbate and glutathione (GSH), and maintained higher content of GSH in glutathione pool (GSH:GSSG) and suppressed the formation of 4-hydroxy-2-nonenal and protein carbonylation, and electrolyte leakage. It may be concluded that NO improved the activity of hydrolyzing and Pro and N-metabolism enzymes. Application of NO also enhanced non-enzymatic antioxidants, and 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity under Cr(VI) toxicity conditions, thereby improved enhanced seed germination and seedlings vigor.

Unprecedented anthropogenic activities have led to contamination of soil and water with toxic metals that present a great threat to crop yields. This situation has compelled researchers to understand metal toxicity responses in order to develop strategies to curtail toxic metal-mediated losses in crop yields. Past decade has witnessed tremendous developments with regard to the role of nitric oxide (NO) in regulating abiotic stresses including toxic metal in crop plants. However, mechanisms related with NO-mediated mitigation of metal toxicity are still less known, and thus investigation in this domain remains underway. Therefore, in this study potential of NO along with its mechanisms of action in mitigating hexavalent chromium [Cr(VI)] toxicity in tomato roots were investigated. Root length and dry weight were declined by Cr(VI) which coincided with increased accumulation of Cr. Major amount of Cr was in the cell wall fraction followed by soluble (including vacuoles) and cell organelles fraction and thus, leading to the cell death in roots. Further, Cr(VI) also declined endogenous NO by inhibiting nitric oxide synthase like activity, and down-regulated ascorbate-glutathione cycle and glutathione biosynthesis, but stimulated oxidative stress markers. In contrast, exogenous addition of NO (as a sodium nitroprusside) reduced toxic effects of Cr(VI) in tomato roots by decreasing Cr accumulation as well as triggering sequestration of Cr into vacuoles and thus collectively protect root from cell death. Moreover, NO also up-regulated ascorbate-glutathione cycle and glutathione biosynthesis, and stimulated phytochelatins, but greatly declined oxidative stress markers. Interestingly, addition of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (c-PTIO) further worsened Cr(VI) toxicity, and Cr(VI) toxicity alleviatory effect of NO was partly reversed by the addition of c-PTIO, suggesting that NO has a crucial role in rendering Cr(VI) toxicity tolerance in tomato roots. Collectively, results suggest that NO mitigates Cr(VI) toxicity in tomato roots by reducing Cr and oxidative stress markers accumulation, triggering sequestration of Cr into vacuoles, and up-regulating ascorbate-glutathione cycle and glutathione biosynthesis, and phytochelatins.

As sessile organisms, plants are unable to avoid being subjected to environmental stresses that negatively affect their growth and productivity. Instead, they utilize various mechanisms at the morphological, physiological, and biochemical levels to alleviate the deleterious effects of such stresses. Amongst these, secondary metabolites produced by plants represent an important component of the defense system. Secondary metabolites, namely phenolics, terpenes, and nitrogen-containing compounds, have been extensively demonstrated to protect plants against multiple stresses, both biotic (herbivores and pathogenic microorganisms) and abiotic (e.g. drought, salinity, and heavy metals). The regulation of secondary metabolism by beneficial elements such as silicon (Si) is an important topic. Silicon-mediated alleviation of both biotic and abiotic stresses has been well documented in numerous plant species. Recently, many studies have demonstrated the involvement of Si in strengthening stress tolerance through the modulation of secondary metabolism. In this review, we discuss Si-mediated regulation of the synthesis, metabolism, and modification of secondary metabolites that lead to enhanced stress tolerance, with a focus on physiological, biochemical, and molecular aspects. Whilst mechanisms involved in Si-mediated regulation of pathogen resistance via secondary metabolism have been established in plants, they are largely unknown in the case of abiotic stresses, thus leaving an important gap in our current knowledge.

Sugar beet (Beta vulgaris L.) is the second most abundant sugar crop after sugarcane. Two field experiments were conducted at the research farm of the Faculty of Agriculture, Saba Basha, Alexandria, Egypt, to study the effects of foliar application treatments and boron (B) fertilizer applications on monogerm sugar beet plants (cultivar classic) during the 2017/2018 and 2018/2019 seasons. The treatments were replicated three times in a split-plot design. Four foliar applications [fulvic acid (FvA), NPK nanoparticles (NPK NPs), FvA + NPK NPs, and a control (water)] were randomly allocated to the main plots. Different numbers of foliar spray applications of B [one application at 120 days after sowing or two applications at 120 and 150 days after sowing, as well as a control (water)] were assigned within the subplots. FvA + NPK NPs significantly increased the root length, root diameter, root weight, and root/shoot ratio of the sugar beet plants; the greatest values were obtained by spraying FvA + NPK NPs during both seasons. B significantly increased the root yield, shoot yield, and biological yield, and two applications of B resulted in the greatest values of root yield, shoot yield, biological yield, and quality of sugar beet. The interaction between FvA or NPK NPs and B significantly affected the yield and quality parameters of the sugar beet plants. However, the greatest mean values of these traits resulted from foliar applications of FvA + NPK NPs in conjunction with applications of B under the conditions at Alexandria, Egypt.

The beneficial roles of melatonin (Mel) and gibberellic acid (GA3) in the biosynthesis of photosynthetic pigments, osmoregulation, and methylglyoxal (MG) detoxification and antioxidant system were studied in tomato (Solanum lycopersicum L. cv. Five Star) seedlings under NaCl stress. The exogenous application of Mel (100 µM) and GA3 (1.4 µM) together more efficiently affected growth performance of seedlings under salt stress. The decreased chlorophyll (Chl) degradation and Chl-degrading enzyme (chlorophyllase) activity in seedlings receiving Mel plus GA3 resulted in increased Chl content by upregulating Chl synthesizing enzyme (δ-aminolevulinic acid dehydratase) under salinity. Exogenous Mel plus GA3 suppressed the overproduction of reactive oxygen species (ROS; superoxide and hydrogen peroxide) and activity of glycolate oxidase. Application of Mel with GA3 reduced MG content by enhancing the activity of enzymes (glyoxalase I and glyoxalase II) involved in the MG detoxification system. Both Mel and GA3 together protected seedlings from ROS induced damage by regulating Δ1-pyrroline-5-carboxylate synthetase activity, and content of proline (Pro) and glycine betaine (GB). Seedlings receiving Mel + GA3 exhibited a substantial upregulated activity of catalase, ascorbate peroxidase, glutathione reductase, dehydroascorbate reductase, monodehydroascorbate reductase, glutathione peroxidase, polyphenol oxidase and lipoxygenase, and redox homeostasis that reduced oxidative damage induced by salinity. These outcomes advocate that Mel and GA3 played beneficial roles in Chl, Pro and GB biosynthesis, and improved redox homeostasis, and MG detoxification and antioxidant system under salt stress.

Despite numerous reports on the role of nitric oxide (NO) in regulating plants growth and mitigating different environmental stresses, its participation in sulfur (S) -metabolism remains largely unknown. Therefore, we studied the role of NO in S acquisition and S-assimilation in tomato seedlings under low S-stress conditions by supplying NO to the leaves of S-sufficient and S-deficient seedlings. S-starved plants exhibited a substantial decreased in plant growth attributes, photosynthetic pigment chlorophyll (Chl) and other photosynthetic parameters, and activity of enzymes involved in Chl biosynthesis (δ-aminolevulinic acid dehydratase), and photosynthetic processes (carbonic anhydrase and RuBisco). Also, S-deficiency enhanced reactive oxygen species (ROS) (superoxide and hydrogen peroxide) and lipid peroxidation (malondialdehyde) levels in tomato seedlings. Contrarily, foliar supplementation of NO to S-deficient seedlings resulted in considerably reduced ROS formation in leaves and roots, which alleviated low S-stress-induced lipid peroxidation. However, exogenous NO enhanced proline accumulation by increasing proline metabolizing enzyme (Δ1-pyrroline-5-carboxylate synthetase) activity and also increased NO, hydrogen sulfide (a gasotransmitter small signaling molecule) and S uptake, and content of S-containing compounds (cysteine and reduced glutathione). Under S-limited conditions, NO improved S utilization efficiency of plants by upregulating the activity of S-assimilating enzymes (ATP sulfurylase, adenosine 5-phosphosulfate reductase, sulfide reductase and O-acetylserine (thiol) lyase). Under S-deprived conditions, improved S-assimilation of seedlings receiving NO resulted in improved redox homeostasis and ascorbate content through increased NO and S uptake. Application of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxy l-3-oxide (an NO scavenger) invalidated the effect of NO and again caused low S-stress-induced oxidative damage, confirming the beneficial role of NO in seedlings under S-deprived conditions. Thus, exogenous NO enhanced the tolerance of tomato seedlings to limit S-triggered oxidative stress and improved photosynthetic performance and S assimilation.

Environmental fluctuations due to anthropogenic activities show negative effects on plant growth and crop production. Among the heavy metals, cadmium (Cd) pollution is most dangerous and is devastating most of the cultivable land. The current study evaluated the Cd induced toxicity in Lycopersicon esculentum plants and the mitigating role of rhizobacteria. Different parameters such as metal uptake, metal chelators, oxidative stress markers, antioxidative defense expression, secondary metabolites, H2O2 tagging, MDA localization and cell viability has been assessed. Cd accumulation enhanced by 64.7% in roots and 267.1% in shoots, which resulted in generating oxidative burst measured in the terms of superoxide content (54.5%), H2O2 (255.1%), and MDA (202.2%) content. Moreover, the Cd stress also modulated the activities of enzymatic antioxidants and non-enzymatic antioxidants. In addition, organic acids and metal chelators were also enhanced in plants under the influence of Cd. Inoculation of rhizobacterial strains reduced the Cd uptake in plant parts (roots and shoots), increased heavy metal tolerance index (HMTI) and reduced oxidative stress markers. Also, enzymatic antioxidants such as, SOD, POD, PPO were increased in microbe inoculated plants whereas CAT, GPOX, APOX, GST, DHAR and GR were reduced. In situ immobilization studies were also conducted in root sections of L. esculentum in which Cd localization, H2O2 accumulation, cell viability and MDA accumulation were observed using confocal and visible microscopy. Reduction in the levels of H2O2, MDA and Cd accumulation along with improved cell viability was observed in the rhizobacterial inoculated plants.

Jasmonic acid (JA) is an important phytohormone associated in defense responses against stress. Crop plants experience heavy metal toxicity and needs to be explored to enhance the crop production. Lead (Pb) is one of the dangerous heavy metal that pollutes soil and water bodies and is released from various sources like discharge from batteries, automobile exhaust, and paints. The present study was designed to evaluate the role of JA (100 nM) on photosynthetic pigments, secondary metabolites, organic acids, and metal ligation compounds in tomato seedlings under different concentrations of Pb (0.25, 0.50, and 0.75 mM). It was observed that Pb treatment declined pigment content, relative water content, and heavy metal tolerance index. Expression of chlorophyllase was also enhanced in Pb-treated seedlings. Seeds primed with JA lowered the expression of chlorophyllase under Pb stress. JA application enhanced the contents of secondary metabolites (total phenols, polyphenols, flavonoids, and anthocyanin) which were confirmed with enhanced expression of chalcone synthase and phenylalanine ammonia lyase in Pb-exposed seedlings. Treatment of JA further elevated the levels of organic acids and metal chelating compounds under Pb toxicity. JA up-regulated the expression of succinate dehydrogenase and fumarate hydratase in Pb-exposed seedlings. Results revealed that seeds primed with JA reduced Pb toxicity by elevating, the levels of photosynthetic pigments, secondary metabolites, osmolytes, metal ligation compounds, organic acids, and polyamine accumulation in tomato seedlings.

The fertilizers that are derived from seaweed are known as Seaweed Liquid Fertilizers (SLF). SLF is a modern, cheap, non-toxic, and natural bioactive fertilizer. Among different studied seaweeds, Ascophyllum nodosum is significant as having bioactive ingredients that potentially regulate the molecular, physiological, and biochemical processes of crop plants. In the present study, the effects of the application of different concentrations (0.00%, 0.01%, 0.02%, 0.05%, 0.10%, 0.50%, and 1.00%) of A. nodosum Extract (ANE) to the Vigna aconitifolia through roots (Pot Root Application, PRA) and on the leaves (Pot Foliar Application, PFA) were monitored via the plant growth. The lower concentrations of ANE in both the PRA and PFA experiments showed positive growth on V. aconitifolia. The 0.10% ANE stimulated the maximum shoot growth when applied through the roots, while 0.05% ANE in both PFA and PRA experiments led to an increase in the number of pods, nodules, organic content, and moisture percentage. The 0.10% ANE also increased the leaf numbers, leaf area, and photosynthetic pigments. Hence, the application of 0.05% and 0.10% of A. nodosum extract in two ways (i.e., Pot Foliar Application, PFA, and Pot Root Application, PRA) ameliorated the growth capabilities of V. aconitifolia.

Potassium (K+) is an important macro-nutrient for plants, which comprises almost 10% of plant's dry mass. It plays a crucial role in the growth of plants as well as other important processes related to metabolism and stress tolerance. Plants have a complex and well-organized potassium distribution system (channels and transporters). Cotton is the most important economic crop, which is the primary source of natural fiber. Soil deficiency in K+ can negatively affect yield and fiber quality of cotton. However, potassium transport system in cotton is poorly studied. Current study identified 43 Potassium Transport System (PTS) genes in Gossypium raimondii genome. Based on conserved domains, transmembrane domains, and motif structures, these genes were classified as K+ transporters (2 HKTs, 7 KEAs, and 16 KUP/HAK/KTs) and K+ channels (11 Shakers and 7 TPKs/KCO). The phylogenetic comparison of GrPTS genes from Arabidopsis thaliana, Glycine max, Oryza sativa, Medicago truncatula and Cicer arietinum revealed variations in PTS gene conservation. Evolutionary analysis predicted that most GrPTS genes were segmentally duplicated. Gene structure analysis showed that the intron/exon organization of these genes was conserved in specific-family. Chromosomal localization demonstrated a random distribution of PTS genes across all the thirteen chromosomes except chromosome six. Many stress responsive cis-regulatory elements were predicted in promoter regions of GrPTS genes. The RNA-seq data analysis followed by qRT-PCR validation demonstrated that PTS genes potentially work in groups against environmental factors. Moreover, a transporter gene (GrHAK/KUP/KT8) and two channel genes (GrAKT2.1 and GrAKT1.1) are important candidate genes for plant stress response. These results provide useful information for further functional characterization of PTS genes with the breeding aim of stress-resistant cultivars.

An experiment was conducted in both laboratory (germinative attributes) and field conditions (growth attributes) with completely randomized design (CRD) and randomized block design, respectively, to view the responses of different priming treatments in two wheat varieties: HUW-234 (V1) and BHU-3(V2). In the present study, seeds were primed with water (hydro, T2), Mg (NO3)2 (T3), ZnSO4 (T4), and a combination of both salts (T5). Their carry over effects were observed on the germinative and vegetative phases of growth. All treatments were compared with the performance of nonprimed control seeds (T1). Maximum germination percentage (98.33, 100%) was noted with T3, whereas length of shoot (8.83, 10.23 cm) and root (9.47, 10.73 cm) and their fresh (0.34, 0.45 g) and dry weights (0.05, 0.07 g) were recorded maximum in T5 for both varieties, however, the vigor index I and II showed varietal difference, but primed sets were found always superior with respect to nonprimed control. Study of plant height, leaf number and area, fresh and dry weights of total leaves and stem showed the best performance under combined use of both salts, i.e., Mg (NO3)2 and ZnSO4 as priming agents, followed by ZnSO4, Mg (NO3)2, hydro, and the nonprimed one. The study of biochemical parameters such as protein content and nitrate reductase activity of leaves showed the highest increment in combined priming treatment and increased 63.77, 90.37, 37.44% and 12.81, 5.61, 7.75%, respectively, after 35, 45, and 60 days after sowing. It is likely that chlorophyll, nitrogen, iron, and zinc content also followed a similar pattern and were enhanced in combined priming treatments as compared to nonpriming treatment. Therefore, the result suggests that priming seeds with Mg (NO3)2 and ZnSO4 worked synergistically at varietal level and improved growth attributes at field conditions.

Globally, the availability of phosphorus (P) to crops remains limited in two-thirds of the soils, which makes it less accessible to plants and ultimately associated with low crop yields. The present study investigated the effect of phosphorus-solubilizing bacteria (PSB, Pseudomonas spp.) for the improvement of phosphorus in mung bean (Vigna radiata) varieties and growth of net grain and biological yields. Results showed that inoculation of mung bean varieties with PSB at the rate of 100 g/kg seed significantly improved the root and shoot dry weight of about 1.13 and 12.66 g, root and shoot length of 14.49 and 50.63 cm, root and shoot phosphorus content of 2629.39 and 4138.91 mg/kg, a biological yield of 9844.41 kg/ha, number of pods of 17 per plant, number of grains of 9 per pod, grain yield of 882.23 kg/ha, and 1000-grain weight of 46.18 g after 60 days of observation. It was also observed that PSB-treated varieties of mung bean showed the maximum photosynthetic yield, photosynthetic active radiation, electron transport rate, and momentary fluorescent rate of 0.75, 364.32, 96.12, and 365.33 μmol/m2 s, respectively. The highest harvest index of 13.28% was recorded by P-treated mung beans. Results disclosed that inoculation of seeds of mung bean with PSB exhibited different effects in measured parameters. It is concluded that PSB possessed remarkable results in measured parameters compared to the control and highlighted that PSB could be an effective natural sustainable fertilizer for mung bean cultivation in sandy soil.

There is little information available to decipher the interaction between molybdenum (Mo) and nitric oxide (NO) in mitigating arsenic (AsV) stress in plants. The present work highlights the associative role of exogenous Mo and endogenous NO signaling in regulating AsV tolerance in wheat seedlings. Application of Mo (1 μM) on 25-day-old wheat seedlings grown in the presence (5 μM) or absence of AsV stress caused improvement of photosynthetic pigment metabolism, reduction of electrolytic leakage and reactive oxygen species (ROS), and higher accumulation of osmolytes (proline and total soluble sugars). The molybdenum treatment upregulated antioxidative enzymes, such as superoxide dismutase, ascorbate peroxidase and glutathione reductase. In addition, the accumulation of nonenzymatic antioxidants (ascorbate and glutathione) was correlated with an increase in ascorbate peroxidase and glutathione reductase activity. The application of cPTIO (endogenous NO scavenger; 100 μM) reversed the Mo-mediated effects, thus indicating that endogenous NO may accompany Mo-induced mitigation of AsV stress. Mo treatment stimulated the accumulation of endogenous NO in the presence of AsV stress. Thus, it is evident that Mo and NO-mediated AsV stress tolerance in wheat seedlings are primarily operative through chlorophyll restoration, osmolytes accumulation, reduced electrolytic leakage, and ROS homeostasis.

Silver nanoparticles (Ag. NPs) have shown a biological activity range, synthesized under different environment-friendly approaches. Ag. NPs were synthesized using aqueous crude extract (ACE) isolated from Plantago lanceolata. The ACE and Ag. NPs were characterized and assessed their biological and antioxidant activities. The existence of nanoparticles (NPs) was confirmed by color shift, atomic force microscopy (AFM), and UV–Vis’s spectroscopy. The FT-IR analysis indicated the association of biomolecules (phenolic acid and flavonoids) to reduce silver (Ag+) ions. The SEM study demonstrated a sphere-shaped and mean size in the range of 30 ± 4 nm. The EDX spectrum revealed that the Ag. NPs were composed of 54.87% Ag with 20 nm size as identified by SEM and TEM. AFM has ended up being exceptionally useful in deciding morphological elements and the distance across of Ag. NPs in the scope of 23–30 nm. The TEM image showed aggregations of NPs and physical interaction. Ag. NPs formation also confirmed by XPS, DRS and BET studies. Ag. NPs showed efficient activity as compared to ACE, and finally, the bacterial growth was impaired by biogenic NPs. The lethal dose (LD50) of Ag. NPs against Agrobacterium tumefaciens, Proteus vulgaris, Staphylococcus aureus, and Escherichia coli were 45.66%, 139.71%, 332.87%, and 45.54%, with IC50 (08.02 ± 0.68), (55.78 ± 1.01), (12.34 ± 1.35) and (11.68 ± 1.42) respectively, suppressing the growth as compared to ACE. The antioxidant capacity, i.e., 2,2-diphenyl-1-picrylhydrazyl (DPPH) of Ag. NPs were assayed. ACE and Ag. NPs achieved a peak antioxidant capacity of 62.43 ± 2.4 and 16.85 ± 0.4 μg mL−1, compared to standard (69.60 ± 1.1 at 100 μg mL−1) with IC50 (369.5 ± 13.42 and 159.5 ± 10.52 respectively). Finally, the Ag. NPs synthesized by P. lanceolata extract have an excellent source of bioactive natural products (NP). Outstanding antioxidant, antibacterial activities have been shown by NPs and can be used in various biological techniques in future research.

Owing to the active use of rare-earth elements in many areas, it is necessary to study their behavior in the environment and their biological impact on plants. Despite the role of melatonin and sulfur in plant growth, development and abiotic stress tolerance; it is still not clear how they have a strong regulatory influence and synergistic effect on growth, physiological and biochemical characteristics of plants under different environmental stresses. Therefore, this study highlights how melatonin and sulfur together potentially involved in a reversal of lanthanum-inhibited photosynthetic and growth responses in tomato seedlings. Here, we reported that seedlings grown in a medium containing 150 μM lanthanum exhibited increased overproduction of reactive oxygen species (ROS) and lipid peroxidation together with increased Chlorophyll degradation, and activity of chlorophyllase, proline dehydrogenase and glycolate oxidase (GOx), and decreased photosynthesis and growth. However, the application of melatonin and sulfur showed significant responses on tomato seedlings, although the response of their combined treatment was more effective by further increasing photosynthesis and growth under lanthanum toxicity. Melatonin supplied with sulfur suppressed ROS formation, lipid peroxidation and activity of GOx, and increased photosynthesis by upregulating activities of carbonic anhydrase and ribulose-1,5-bisphosphate carboxylase/oxygenase. Also, sulfur supplementation with melatonin to seedlings resulted in an elevation in the accumulation of Chl and proline by increasing δ-aminolevulinic acid and activity of δ-aminolevulinic acid dehydratase and Δ1-pyrroline-5-carboxylate synthetase activity. The administration of melatonin with sulfur substantially induced upregulation of enzymes (superoxide dismutase, ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase) activities involved in the antioxidant system, thereby mitigating ROS-induced oxidative damage. Thus, this study provides strong evidence that melatonin and sulfur have strong regulatory influence and synergistic role in alleviating the adverse effect of lanthanum-toxicity by increasing photosynthesis and growth.

Due to the global warming, rising temperature became a serious threat to the world agriculture. Faba bean plant is very susceptible to heat stress and performs poorly under high temperature condition. Therefore, the performance of faba bean (Vicia faba L.), genotype ‘C5’ was tested to explore (i) the biosynthesis of proline (Pro) in response to heat stress (HS) and the involvement of nitric oxide (NO) and Pro in thermotolerance mechanism and (ii) the role of heat shock proteins (HSPs) and Pro in defense, and their correlation with the tolerance of faba bean plant to HS. Exposure of plants to HS for 48 h resulted in increased levels of reactive oxygen species [hydrogen peroxide (H2O2) and superoxide ions (O2•−)], nitric oxide (NO), accumulation of Pro and malondialdehyde, electrolyte leakage, DNA damage, chlorophyll (Chl) degradation and in decreased leaf relative water content (RWC) and Chl content in faba bean plants. However, at the same time increasing levels of HS (32, 37 and 42 °C) increased the accumulation of NO, Pro, activities of Pro metabolizing enzymes (Δ1-pyrroline-5-carboxylate synthetase, ornithine-δ-aminotransferase and proline dehydrogenase) and expression of HSPs (Hsp17.6, Hsp70, Hsp90-1, and Hsp101). Induced biosynthesis of NO and Pro under HS activated defense system of plants by enhancing the activities of antioxidant enzymes [superoxide dismutase, catalase, glutathione reductase and ascorbate peroxidase] and also by increasing the content of reduced glutathione (GSH), ascorbate (AsA) and oxidized glutathione (GSSG). While, an increase in GSSG content was found lesser than an increase in GSH under HS stress. Application of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO; an NO scavenger) decreased the accumulation of leaf RWC and Pro and NO. Therefore, it can be proposed that NO acts as both signal molecule and promotor of Pro biosynthesis. The present investigation reveals that above studied parameters could be used in identifying a HS-tolerant plant that can be utilized in future breeding programs.

The effects of magnesium (Mg) supplementation on the growth performance, oxidative damage, DNA damage, and photosynthetic pigment synthesis, as well as on the activity level of carbonic anhydrase (CA), ribulose-1,5-bisphosphate carboxylase (Rubisco), and antioxidant enzymes were studied in Vicia faba L. plants exposed to heat stress (HS) and non-heat-stress (non-HS) conditions. Seeds were grown in pots containing a 1:1 mixture of sand and peat, with Mg treatments. The treatments consisted of (i) 0 Mg and non-HS (ambient temperature; control); (ii) 50 mM Mg; (iii) HS (38 °C); and (iv) 50 mM Mg and HS (38 °C). HS was imposed by placing potted plants in an incubator at 38 °C for 48 h. Growth attributes, total chlorophyll (Total Chl), and CA, and Rubisco activity decreased in plants subjected to HS, whereas accumulation of organic solutes [proline (Pro) and glycine betaine (GB)]; superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activity; DNA damage; electrolyte leakage (EL); and malondialdehyde (MDA) and hydrogen peroxide (H2O2) content all increased. Application of Mg, however, significantly enhanced further proline (Pro), glycinebetaine (GB), SOD, POD, and CAT activity, and decreased DNA damage, EL, and MDA and H2O2 concentrations. These results suggest that adequate supply of Mg is not only essential for plant growth and development, but also improves plant tolerance to HS by suppressing cellular damage induced by reactive oxygen species through the enhancement of the accumulation of Pro and GB, and the actions of antioxidant enzymes. Keywords: Cellular damage, DNA damage, Faba bean, Heat stress, Magnesium

Silicon (Si) and hydrogen sulfide (H2S) are known to enhance plant defense against multiple stresses. Current study was conducted to investigate the application of Si and H2S alone as well as in combination, improved physiological resilience of wheat plants to drought stress (DS) and pathogen-Puccinia triticina (Pt) infection. We aimed to increase the wheat plant growth and to enhance the DS tolerance and Pt resistance with the concurrent applications of H2S and Si. In the first experiment, we selected the best growth enhancing concentration of H2S (0.3 mM) and Si (6 mM) to further investigate their tolerance and resistance potential in the pot experiment under DS and pathogen infection conditions. The obtained results reveal that DS has further increased the susceptibility of wheat plants to leaf rust pathogen infection while, the sole application of Si and the simultaneous exogenous treatments of H2S + Si enhanced the plant growth, decreased disease incidence, and significantly improved tolerance and defense mechanisms of wheat under individual and interactive stress conditions. The exogenous treatment of H2S + Si improved the growth criteria, photosynthetic pigments, osmoprotectants, and defense related enzyme activities. The same treatment also reinforced the endogenous H2S, Si, ABA and SA contents while decreased the disease incidence and oxidative stress indicators under individual and combined stress conditions. Overall, results from this study presents the influence of combined drought and P. triticina stress in wheat and reveal the beneficial impacts of concurrent exogenous treatment of H2S + Si to mitigate the drought and pathogen (P. triticina) induced adverse effects.

Plant growth regulators and Rhizobium are actively involved in the regulation of flowering, pod formation, nodulation, and ultimately the growth and yield of legumes. However, very limited information is available on the combined effect of gibberellic acid (GA3) and Rhizobium on growth attributes and yield of legume crops. This experiment was designed to fill this gap by studying the performance of chickpea under exogenous application of GA3 (10−4 and 10−5 M) alone and in combination with Rhizobium. Exogenous application of GA3 (10−5 M) combined with rhizobium inoculation gave the highest values for number of nodules per plant (16) and their dry biomass (0.22 g). Moreover, GA3 application and seed inoculation with Rhizobium, when applied singly, significantly enhanced chickpea growth. However, the most promising results were obtained by the inoculation of Rhizobium accompanied with GA3 (10−5 M). Plant height, grain and stover yield, and chlorophyll contents were enhanced up to 35%, 39%, 21%, and 51%, respectively. Likewise, the bioaccumulation of macronutrients (N, P and K) was maximum in plants receiving both Rhizobium inoculation and GA3 application. It is concluded that the combined application of Rhizobium and GA3 has synergistic effects on the growth, yield, and nutrient contents of chickpea.

Environmental factors impair plant growth and development, and cause a massive reduction in agricultural production globally. Naturally, plants are sessile and encounter various environmental stresses such as salinity, drought, temperature nutrient deficiency, and biotic soil environment. Plants have developed complex signaling mechanisms to cope with these stresses, consisting of several elements, including phytohormones. Recently, Strigolactones (SLs) have emerged as a driving force, regulating plant growth and developmental processes, and play a vital role in addressing environmental stresses. At first, SLs were identified as harmful agents for plants due to their restorative role in the seed development of parasitic plants; however, a beneficial role in plant growth and development was discovered later on. Therefore, SLs are considered as crucial hormones for maintaining plant architecture by modulating root and shoot generation in response to several stresses. Nevertheless, the engineering of regulation and biosynthesis of the SLs pathway makes it a more suitable hormone to develop genetically manipulated plants with improved environmental stress tolerance. Here, we have discussed the biosynthesis of SLs and their regulatory role in response to various stresses. Knowledge of the signaling mechanisms of SLs could be useful for future crop improvement programs.

Climate change is the leading cause of crop yield losses worldwide. Recent progression in plant biology and ground-breaking molecular and biochemical procedures have increased our understanding of phytohormonal signaling in response to numerous abiotic stresses, including heavy metals (HMs) toxicity in plants. HMs toxicity owns numerous harmful effects on plant health, including growth inhibition, reduction in biomass production, leaves chlorosis, imbalance of nutrients, and water contents, ultimately causing leaf senescence and plant death. Jasmonates (JAs) are naturally occurring lipid-derived hormones that normalize global plant growth and development under HMs toxicity. Notably, JAs as vital growth controllers are involved in numerous physiological, biochemical, and molecular mechanisms in plants. JAs alone or occasionally in grouping with other phytohormones upgrade the stress tolerance system in plants. As a whole, JAs can secure plants from the harmful effects of HMs toxicity through the up-regulation of JA-associated gene expression and several physiological and biochemical mechanisms. Moreover, JAs can uphold the veracity of plant cells in response to different HMs by increasing the antioxidant defense systems and biosynthesis of some osmoprotectants. In this chapter, we have discussed the JA biosynthesis and metabolisms, its beneficial role in response to several HMs, its crucial role as antioxidant defense, and its cross-talk with other phytohormones have been explained.

Linseed is an important industrial crop cultivated for its edible seeds and fiber linen. Organic fertilizers have beneficial effects on soil properties and quality of crops. Therefore, we conducted two field experiments during 2018&ndash, 2019 and 2019&ndash, 2020 to determine the effect of organic fertilizers on soil fertility, yield and fiber quality of linseed varieties Roshni, BL1 and Chandni under low soil moisture conditions. We prepared organic fertilizers from seed cake of Eruca sativa, leaves of Moringa oleifera and chicken peat in various combinations by composting method. The various formulations of organic fertilizers included OF1(1 kg seed cake of Eruca sativa), OF2 (1 kg seed cake of Eruca sativa +1 kg chicken peat), OF3 (1 kg seed cake of Eruca sativa + 0.5 kg chicken peat + 0.25 kg Moringa oliefera leaves) and OF4 (1 kg seed cake of Eruca sativa + 0.250 kg chicken peat + 0.5 kg Moringa oliefera leaves). Compositional analysis of organic fertilizers indicated that OF3 and OF4 had higher and may potentially sufficient quantities of NPK and organic matter. Both of these fertilizers significantly improved soil total N, available P, K, Zn and Fe contents. Growth response of linseed varieties to organic fertilizers was evaluated under water deficit stress (40% field capacity of soil) at tillering stage for one month. Water stress had significantly adverse effects on plant height, production of tillers per plant, leaf relative water content (LRWC), number of capsules per plant, thousand seed weight, total seed yield, straw yield, fiber length and fiber weight of linseed varieties. However, the application of OF3 and OF4 significantly enhanced plant height, tillers production, LRWC, seed yield, straw yield, fiber length and fiber weight under water deficit stress. Water deficit stress also resulted in a significant increase in the content of phenolics of both the leaves and roots. For each measured quality parameter of linseed varieties, organic fertilizer treatments resulted in higher values than untreated and irrigated control. We concluded that organic fertilizers particularly OF3 and OF4 significantly improved soil fertility and minimized negative effect of water deficit stress on plant height, tillers production, LRWC, seed yield, straw yield, fiber length and fiber weight of linseed varieties.

Numerous cropping systems of the world are experiencing the emergence of new weed species in response to conservation agriculture. Conyza stricta Willd. is being a newly emerging weed of barley-based cropping systems in response to conservational tillage practices. Seed germination ecology of four populations (irrigated, rainfed, abandoned and ruderal habitats) was studied in laboratory and greenhouse experiments. The presence/absence of seed dormancy was inferred first, which indicated seeds were non-dormant. Seed germination was then recorded under various photoperiods, constant and alternating day/night temperatures, and pH, salinity and osmotic potential levels. Seedling emergence was observed from various seed burial depths. Seeds of all populations proved photoblastic and required 12-hour light/dark period for germination. Seeds of all populations germinated under 5–30°C constant temperature; however, peak germination was recorded under 17.22–18.11°C. Nonetheless, the highest germination was noted under 20/15°C alternating day/night temperature. Ruderal and irrigated populations better tolerated salinity and germinated under 0–500 mM salinity. Similarly, rainfed population proved more tolerant to osmotic potential than other populations. Seeds of all populations required neutral pH for the highest germination, whereas decline was noted in germination under basic and alkaline pH. Seedling emergence was retarded for seeds buried >2 cm depth and no emergence was recorded from >4 cm depth. These results add valuable information towards our understanding of seed germination ecology of C. stricta. Seed germination ability of different populations under diverse environmental conditions suspects that the species can present severe challenges in future if not managed. Deep seed burial along with effective management of the emerging seedlings seems a pragmatic option to manage the species in cultivated fields. However, immediate management strategies are needed for rest of the habitats.

Petroleum hydrocarbon (PHC) contamination of soil is a widespread global environmental concern due to the persistence and recalcitrant nature of PHCs. The PHCs are highly toxic and their removal from the terrestrial ecosystem is necessary to maintain soil as well as human health. Here, a pot experiment was performed to examine the impact of Enterobacter sp. MN17 and biochar addition on the growth of mungbean plants and PHCs removal from diesel-polluted soil. For this purpose, soil was contaminated artificially with diesel to achieve a final concentration of 5000 mg kg&minus, 1. Untreated and Enterobacter sp. MN17 treated mungbean seeds were sown in pots. Sugarcane bagasse biochar was applied as an amendment in respective pots along with the recommended levels of essential nutrients. Results showed that PHCs significantly suppressed the seedling emergence as well as agronomic and physiological attributes of mungbean as compared to un-contaminated controls. However, the co-application of Enterobacter sp. MN17 and biochar significantly reduced the phytotoxicity of PHCs to mungbean plants and effectively increased the seedling emergence, shoot and root length, shoot fresh and dry biomass, root fresh and dry biomass of plants up to 24%, 54%, 52%, 52%, 54%, 55% and 60%, respectively as compared to controls. Similarly, 30%, 57%, 64%, 36% and 57% increase in chlorophylls contents, transpiration rate, stomatal conductance, sub-stomatal conductance, and photosynthetic rate, respectively were observed in their combined application as compared to respective controls. Furthermore, the co-addition of biochar and Enterobacter sp. MN17 could remove 69% and 85% higher PHCs from unplanted and planted pots, respectively, than that of their respective controls. Our results suggest that the co-application of biochar and Enterobacter sp. MN17 may be useful in enhancing plant growth and eliminating PHCs from contaminated soil.

A supply of plant micronutrients (some of which are metals) is necessary to regulate many plant processes; their excess, however, can have detrimental consequences and can hamper plant growth, physiology and metabolism. Artemisia annua is an important crop plant used in the treatment of malaria. In this investigation, the physio-biochemical mechanisms involved in exogenous hydrogen sulphide-mediated (H2 S) alleviation of copper (Cu) stress in A. annua were assessed. Two different levels of Cu (20, 40 mg·kg-1 ), one H2 S treatment (200 µm) and their combinations were introduced while one set of plants was retained as control. Results showed that the presence of excess Cu in the soil reduced growth and biomass, photosynthetic parameters, chlorophyll content and fluorescence, gas exchange parameters and induced antioxidant enzyme activity. Copper stress enhanced the production of thiobarbituric acid reactive substances (TBARS) and increased Cu content in both roots and shoots of affected plants. Exogenous application of H2 S restored the physio-biochemical characteristics of Cu-treated A. annua plants by reducing lipid peroxidation and enhancing the activity of antioxidant enzymes in Cu-stressed plants as compared with the controls. Hydrogen sulphide also reduced the Cu content in different plant parts, increased photosynthetic efficiency, trichome density, average area of trichomes and artemisinin content. Therefore, our results provide a comprehensive assessment of the defensive role of H2 S in Cu-stressed A. annua.

Management of inorganic fertilizer is very important to obtain maximum crop yield and improved nutrient use efficiency in cereal crops. Fixation of phosphatic fertilizers in alkaline soils due to calcareousness is one of the major hurdles. It induces phosphorus nutritional stress that can decrease the yield of maize and wheat. Selection of a suitable application method and proper stage of crop for phosphorus (P) fertilizer has prime importance in better uptake of P and crop production. Among different application methods, soil and foliar application are widely adopted. In wheat and maize, knee height + tasseling and stem elongation + booting are critical stages towards P deficiency. That is why field trials were conducted to evaluate the supplemental effect of foliar P on maize and wheat yields. For that, 144 mM KH2PO4 was applied as foliar at knee height + tasseling and stem elongation + boot stages in maize and wheat, respectively. Soil application of 0, 20, 40 and 60 kg P ha&minus, 1 was done through broadcast and band methods. Results showed that foliar spray of 144 mM KH2PO4 at knee height + tasseling and stem elongation + boot stages in wheat and maize significantly enhanced grains yield and phosphorus use efficiency (PUE) where P was applied as banding or broadcast at the time of sowing. A significant decreasing trend in response to increasing soil P levels validated the efficacious role and suitability of foliar P. In conclusion, the use of P as foliar at knee height + tasseling and stem elongation + boot stages is an efficacious way to manage P fertilizer.

Hydrogen sulfide (H2S) and nitric oxide (NO) have been known to affect vast number of processes in plants under abiotic stresses. Also, calcium (Ca) works as a second messenger in plants, which underpins the abiotic stress-induced damage. However, the sequence of action of these signaling molecules against cadmium (Cd)-induced cellular oxidative damage remains unidentified. Therefore, we studied the synergistic actions and/or relationship of signaling molecules and Ca-dependent activation of tolerance mechanisms in Vigna radiata seedlings under Cd stress. The present study shows that exogenous Ca supplemented to Cd-stressed V. radiata seedlings reduced Cd accumulation and improved the activity of nitrate reductase, and L/D-cysteine desulfhydrase (LCD/DCD) that resulted in improved synthesis of NO and H2S content. Application of Ca also elevated the level of cysteine (Cys) by upregulating the activity of Cys-synthesizing enzymes serine acetyltransferase and O-acetylserine(thiol)lyase in Cd-stressed seedlings. Maintenance of Cys pool under Cd stress contributed to improved H2S content which together with Ca and NO improved antioxidant enzymes and components of ascorbate-glutathione (AsA-GSH) cycle. All these collectively regulated the activity of NADPH oxidase and glycolate oxidase, resulting in the inhibition of Cd-induced generation of reactive oxygen species. The elevated level of Cys also assisted the Cd-stressed seedlings in maintaining GSH pool which retained normal functioning of AsA-GSH cycle and led to enhanced content of phytochelatins coupled with reduced Cd content. The positive effect of these events manifested in an enhanced rate of photosynthesis, carbohydrate accumulation, and growth attributes of the plants. On the contrary, addition of NO scavenger cPTIO [2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide], H2S scavenger HT (Hypotaurine) and Ca-chelator EGTA (Ethylene glycol-bis(b-aminoethylether)-N,N,N',N'-tetraacetic acid) again developed a condition similar to stress and positive effect of the signaling molecules was abolished. The findings of the study postulate that Ca in association with NO and H2S mitigates Cd-induced impairment and enhances the tolerance of the V. radiata plants against Cd stress. The results of the study also substantiate that Ca acts both upstream as well as downstream of NO signals whereas, H2S acts downstream of Ca and NO during Cd-stress responses of the plants.

Metal toxicity in crop plants is a matter of scientific concern. Therefore, in recent years efforts have been made to minimize metal toxicity in crop plants. Out of various strategies, priming of seedlings with certain chemicals, like e.g. donors of signaling molecules, nutrients, metabolites or plant hormones has shown encouraging results. However, mechanisms related with the priming-induced mitigation of metal toxicity are still poorly known. Hence, we have tested the potential of 2-oxoglutarate (2-OG) priming in enhancing the arsenate (AsV ) toxicity tolerance in tomato seedlings along with deciphering the probable role of nitric oxide (NO) in accomplishing this task. Arsenate decreased growth, endogenous NO and nitric oxide synthase-like activity but enhanced the accumulation of As, which collectively led to root cell death. Arsenate toxicity also decreased some photosynthetic characteristics (i.e. Fv /Fm, qP, Fv /F0 and Fm /F0 , and total chlorophyll content) but enhanced NPQ. However, priming with 2-OG alleviated the toxic effect of AsV on growth, endogenous NO, cell death and photosynthesis. Moreover, arsenate inhibited the activities of enzymes of nitrogen metabolism (i.e. nitrate reductase, nitrite reductase, glutamine synthetase and glutamine 2-oxoglutarate aminotransferase) but increased the activity of glutamate dehydrogenase and NH4 + content. Superoxide radicals, hydrogen peroxide, lipid peroxidation, protein oxidation and membrane damage increased upon AsV exposure, but the antioxidant enzymes (i.e. superoxide dismutase, catalase and glutathione-S-transferase) showed differential responses. Overall, our results showed that 2-OG is capable of alleviating AsV toxicity in tomato seedlings but the involvement of endogenous NO is probably required.

Maize is considered one of the most imperative cereal crops worldwide. In this work, high throughput silica nanoparticles (SiO2-NPs) were prepared via the sol&ndash, gel technique. SiO2-NPs were attained in a powder form followed by full analysis using the advanced tools (UV-vis, HR-TEM, SEM, XRD and zeta potential). To this end, SiO2-NPs were applied as both nanofertilizer and pesticide against four common pests that infect the stored maize and cause severe damage to crops. As for nanofertilizers, the response of maize hybrid to mineral NPK, &ldquo, Nitrogen (N), Phosphorus (P), and Potassium (K)&rdquo, (0% = untreated, 50% of recommended dose and 100%), with different combinations of SiO2-NPs, (0, 2.5, 5, 10 g/kg soil) was evaluated. Afterward, post-harvest, grains were stored and fumigated with different concentrations of SiO2-NPs (0.0031, 0.0063. 0.25, 0.5, 1.0, 2.0, 2.5, 5, 10 g/kg) in order to identify LC50 and mortality % of four common insects, namely Sitophilus oryzae, Rhizopertha dominica, Tribolium castaneum, and Orizaephilus surinamenisis. The results revealed that, using the recommended dose of 100%, mineral NPK showed the greatest mean values of plant height, chlorophyll content, yield, its components, and protein (%). By feeding the soil with SiO2-NPs up to 10 g/kg, the best growth and yield enhancement of maize crop is noticed. Mineral NPK interacted with SiO2-NPs, whereas the application of mineral NPK at the rate of 50% with 10 g/kg SiO2-NPs, increased the highest mean values of agronomic characters. Therefore, SiO2-NPs can be applied as a growth promoter, and in the meantime, as strong unconventional pesticides for crops during storage, with a very small and safe dose.

The interplay between melatonin (Mel) and calcium (Ca) in enhancing tolerance to metalloid toxicity and underlying physiological and biochemical mechanisms of this relationship still remains unknown. The present study reveals that the signaling molecules Mel and/or Ca enhanced tolerance of Vicia faba (cv. Tara) plant to metalloid arsenic (As) toxicity. However, a combination of Mel and Ca was more efficient than alone. Plants grew with As exhibited enhanced hydrogen peroxide, superoxide anion, electrolyte leakage, lipid peroxidation together with increased reactive oxygen species (ROS) producing enzymes, such as NADPH oxidase and glycolate oxidase (GOX). On the contrary, an inhibition in chlorophyll (Chl) biosynthesis and gas exchange parameters (net photosynthetic rate, stomatal conductance, intercellular carbon dioxide concentration) was observed. Under As toxicity conditions, the application of Mel and Ca synergistically suppressed the plants’ program cell death features (nucleus condensation and nucleus fragmentation) in guard cells of stomata, DNA damage, and formation of ROS in guard cells, leaves and roots. Moreover, it enhanced gas exchange parameters and activity of enzymes involved in photosynthesis process (carbonic anhydrase and RuBisco), Chl biosynthesis (δ-aminolevulinic acid dehydratase), and decreased activity of Chl degrading enzyme (chlorophyllase) under As toxicity conditions. Our investigation evidently established that expression of ATP synthase, Ca-ATPase, Ca-DPKase, Hsp17.6 and Hsp40 was found maximum in the plants treated with Mel + Ca, resulting in higher tolerance of plants to As stress. Also, increased total soluble carbohydrates, cysteine, and Pro accumulation with increased Pro synthesizing enzyme (Δ-pyrroline-5-carboxylate synthetase (P5CS) and decreased Pro degrading enzyme (proline dehydrogenase) in Mel + Ca treated plants conferred As toxicity tolerance. The obtained results postulate strong evidence that the application of Mel along with Ca enhances resilience against As toxicity by upregulating the activity of plasma membrane H-ATPase, enzymes involved in antioxidant system, and ascorbate-glutathione pathway., The authors extend their appreciation to the Deanship of Scientific Research at King Saud University for funding this work through Research Group No. RG-1441-438.

Boron (B), an essential micronutrient, helps the plants to complete their life cycle successfully. Therefore, the present experiment was conducted to study (1) the role of B in seed germination and seedling growth, (2) the toxicity effect of B in seed germination and seedling growth and (3) the role of B in tolerance of barley (Hordeum vulgare L. var. ‘Bakore’) to NaCl stress. Under NaCl stress and non-stress conditions, application of high levels of B (100 µM) decreased parameters of germination (G%, VI, GI and MGT), growth (RL, SL, RFW, SFW, RDW and SDW), except the accumulation of Pro and MDA in barley seedlings. Also, a fluorescence study reveals that production of ROS (H2O2 and O2 •—) and non-viable cells increased in roots of barley seedlings treated with NaCl and high dose of B. An alteration in anatomical structure of barley seedlings was observed with the application of NaCl and high dose of B. However, a low concentration of B (50 µM) proved best and increased all germination and growth traits of barley seedlings by increasing further accumulation of Pro. Also, 50 µM of B significantly increased the biosynthesis of photosynthetic pigments (Chl a, b and total Chl) and deceased formation of ROS and viable cells in roots. Therefore, concluded that sufficient dose of B could be beneficial for barley plant in improving the tolerance to NaCl stress.

Among the heavy metals (HMs), lead (Pb) is considered as a toxic HM which adversely affects growth and development of crop plants. The present experiment was aimed to investigate the potential role of ascorbic acid (ASC) in the reversal of Pb-inhibited nitrogen and sulfur assimilation enzymes activity and activity of photosynthesis enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and growth response in wheat plants. Wheat seedlings were subjected to 0 mM (control) and 0.2 mM and 0.6 mM of ASC with and without 2 mM of Pb. Plants treated with Pb exhibited the following reduced growth characteristics (root length, shoot length, root fresh weight (FW), shoot FW, root dry weight (DW) and shoot DW). A decrease was also observed in the activity of Rubisco and ATP sulfurylase (ATP-S), relative water content (RWC), accumulation of total chlorophyll (Total Chl) and content of nutrients [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg)] in Pb-treated plants. However, an increase in Chl degradation and in the activity of O-acetylserine(thiol)lyase (OAS-TL) and accumulation of cysteine (Cys), malondialdehyde (MDA) and hydrogen peroxide (H2O2) was observed in plants under Pb stress. On the contrary, exogenous application of ASC mitigated the Pb-toxicity-induced oxidative damage by enhancing the activities of antioxidant enzymes, such as superoxide dismutase, catalase and glutathione reductase. Improved activity of antioxidant enzymes suppressed the formation of MDA and H2O2, which was reflected in the form of improved growth characteristics. Moreover, ASC induced improvement in plants defense systems by reduced Chl degradation and improved the content of essential nutrients (N, P, K, Ca and Mg) and Cys, RWC and the activity of Rubisco, ATP-S, NR and OAS-TL.

Due to increasing soil salinity, the world agricultural output is being threatened by the shrinking area of fertile land. In the present study, we explored the interactive roles of nitric oxide (NO; 100 μM) and spermidine (SP; 200 μM) in ameliorating the effects of salt stress (NaCl; 100 mM) in tomato (Solanum lycopersicum L. var. Five Star) seedlings. NaCl stress reduced shoot and root length, shoot and root fresh weight, shoot and root dry weight plant -1 and leaf area leaf -1. NaCl stress also suppressed the biosynthesis of photosynthetic pigments (Chlorophyll a and b) and increased proline (Pro) content, membrane damage and lipid peroxidation by inducing reactive oxygen species (H2O2 and O2• - ) generation in roots and leaves, as well as electrolyte leakage (EL) and malondialdehyde (MDA) accumulation in leaves. However, applying NO and/or SP increased the activities of catalase, peroxidase, superoxide dismutase, glutathione reductase and ascorbate peroxidase and increased photosynthetic pigment (chlorophyll a and b) and Pro accumulation, as well as reducing H2O2 and O2• - and MDA content and EL, under salt stress. When tomato plants were treated with NO and SP simultaneously, NO signaling was further enhanced, which was confirmed by the addition of cPTIO [2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; NO scavenger].

Climatic variations adversely affect the limited water resources of earth which leads to water stress and influences agricultural production worldwide. Therefore, a novel approach has been introduced to improve the tolerance against water stress in herbaceous nature medicinal plants such as Coriandrum sativum by the usage of nanotechnology (foliar applied nanoparticles of ZnOx) coupled with the application of water deficit irrigation. This is an alternative water saving strategy that proved to be efficient to mitigate the Coriandrum sativum tolerance against water stress regimes for sustainable yield production through the activation of antioxidant system. Thus, the phenomena of green synthesis have been deployed for the formation of Zinc oxide nanoparticles (ZnOx NPs) from the leaf extract of Camellia sinensis L. and zinc acetate dihydrate was used as precursor. Different techniques have been used for the thorough study and confirmation of ZnOx NPs such as UV-vis spectroscopy (UV-vis) X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and Elemental dispersive spectroscopy (EDS). The prepared ZnOx NPs exhibit hexagonal wurtzite crystal nature has an average size of 37 nm with high purity. These ZnOx NPs have been further studied for their role in amelioration of water stress tolerance in Coriandrum sativum in a pot experiment. Two levels of water stress regimes were employed, IR75 (moderate) and IR50 (Intense) to evaluate the behavior of plant compared to full irrigation (FI). Results showed that under water stress regimes, the 100 ppm of prepared NPs stimulate the antioxidant system by increasing the activity of catalases (CAT), super oxidases (SOD) and ascorbate peroxidase (APX) enzymes and found the maximum at IR50, while the concentration of malondialdehyde (MDA) decreased due to increase in activity of antioxidative enzymes. Furthermore, chlorophyll content and amount of proline also enhanced by the foliar application of prepared ZnOx NPs under moderate water stress (IR75). The results suggested that all the investigated agronomic attributes significantly increased, including plant biomass and economic yield (EY), compared to non-treated ZnOx NPs plants, except for the number of primary branches and LAI. Further, the 100 ppm of prepared ZnOx NPs have great potential to improve water stress tolerance in Coriandrum sativum by improving the antioxidant enzymes activity that enhance agronomic attributes for high crop productivity that require further research at transcriptomic and genomic level.

Sclerotium rolfsii is a soil-borne fungus that causes big losses in productivity of various plant species including Phaseolus vulgaris L. The objectives of this study were to (1) evaluate the impacts of Sclerotium rolfsii on growth and production of common bean plants, (2) determine the effects of Sclerotium rolfsii on nutritive contents of beans, and (3) test the efficacy of bio-inoculants on suppressing plant infection with Sclerotium rolfsii. To fulfill these objectives, we used a coupled pot and field experimental approaches during two growing seasons. Common beans were inoculated with either arbuscular mycorrhizal fungi (Claroideoglomus etunicatum), Saccharomyces cerevisiae, or Trichoderma viride solely or in different combinations. Non-inoculated plants and fungicide treated ones were considered as reference treatments. Throughout these experiments, minimal amounts of rock phosphate were added during soil preparation for bio-inoculated treatments, while the non-inoculated reference treatments received a full dose of P as calcium superphosphate. Results revealed that all tested bioinoculants significantly raised the activities of plant defense enzymes i.e. chitinase, peroxidase and polyphenoloxidase as compared to non-inoculated control. Likewise, pre-, post- and plant survival percentages significantly increased due to these bio-inoculations. Increased survival percentages were attributed to the concurrent increases in uptake of N, P and Zn nutrients by plants treated with bioinoculants. In this concern, plant nutrients uptake was higher in combined than single bio-inoculant treatments. Moreover, the uptake values of plant nutrients owing to the combined bio-inoculants were higher than the corresponding ones achieved due to fungicide treatment. In conclusion, application of the tested bio-inoculants, especially the combined ones can be considered an eco-friendly approach that not only enhances plants resistance against infection with Sclerotium rolfsii but also improves plant nutritive status.

Medicinal plants are of undoubted value, as they have been used for centuries to treat various diseases and health disorders in almost every part of the world. In several studies, the use of medicinal plants was found effective in treatment of infectious and non-infectious diseases. The World Health Organization has been working for many years to identify all surviving medicinal plants on the earth. An important step has also been taken by the Natural Health Product Regulation of Canada for promotion and usages of natural products. At present, the rapidly growing population of the world is facing many challenges from various infectious diseases that are associated with hepatitis A, B and C virus, human immunodeficiency virus, influenza virus, dengue virus and new emerging viruses. Hepatitis B virus causes a severe and frequently transmittable disease of the liver. Millions of people worldwide suffer from hepatitis B virus (HBV) infection. The drugs available on the market for the treatment of hepatitis B are not sufficient and also cause side effects in patients suffering from HBV infection. The pharmaceutical companies are searching for suitable alternative and natural inhibitors of HBV. Therefore, it is important to explore and use plants as a source of new medicines to treat this infectious disease, because single plants contain a priceless pool of active ingredients which could help in the production of pharmaceutical-grade peptides or proteins. However, the knowledge of the antiviral activity of medicinal plants is still limited.

Climate change represents a major threat to agriculture. High ambient temperatures, as a result of global warming, are currently limiting plant growth and development. The aim of the present study was to investigate the effect of sodium nitroprusside (SNP) in combination with indole acetic acid (IAA) on tomato (Lycopersicon esculentum Mill.) plants under heat stress (HS) and non-heat stress (non-HS) conditions. HS is suggested to induce the formation of reactive oxygen species, such as superoxide and hydrogen peroxide, which may lead to genotoxicity by damaging DNA, which can be detected by the comet assay (single-cell gel electrophoresis). HS substantially enhanced proline (Pro), malondialdehyde accumulation, electrolyte leakage (EL), growth reduction, and reduced physiological and biochemical parameters. However, the co-application of SNP and IAA alleviated the adverse effects of HS by promoting catalase, peroxidase, and superoxide dismutase activities and enhancing the accumulation of photosynthetic pigments (chlorophyll a and b) and Pro with a concomitant decrease in H2O2 and $\hbox{O}_ 2^ - $ content, EL, and DNA damage. Conversely, the treatment of tomato plants with the NO scavenger cPTIO [2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide] along with SNP and IAA further reduced the SNP signal. Therefore, these results suggest that the application of SNP with IAA improves plant defense mechanisms against HS.

Environmental stress imposes negative impacts on the growth and development of the crop plants. The present study was designed to assess the effect of PGPR (Pseudomonas aeruginosa and Burkholderia gladioli) on plant pigments and phenolic compounds in 10-days-old root knot nematode (RKN)-infected Lycopersiconesculentum seedlings. The levels of different osmoprotectants and organic acids were also evaluated in nematode-infected L. esculentum seedlings. Our results revealed that nematode-infected seedlings had reduced levels of plant pigments(chlorophyll (70.5%), carotenoids (64.8%), and xanthophylls (34.3%)) and enhanced levels of phenolic compounds(total phenols (40.3%), flavonoids (80.9%), anthocyanins (28.9%), and polyphenols (366.1%)), osmoprotectants(total osmolytes (15.3%), total carbohydrates (54.9%), reducing sugars (45.3%), trehalose (94.5%), glycine betaine (59.01%) and proline (69.6%) and (citric acid (28.4%), fumaric acid (18.16%), succinic acid (179.9%), and malic acid (21.7%)). The levels of these metabolites increased after inoculation with P. aeruginosa and B. gladioli. The expression of genes encoding different enzymes pertaining to phenols and organic acid metabolism were also studied. The expression of genes was elevated in nematode-infected plants i.e. CHS (chalcone synthase) by 1.32 folds, PAL (phenylalanine ammonia lyase) by 1.16 folds, CS (citrate synthase)1.6 folds, SUCLG1 (succinyl Co-A ligase) by 1.19 folds, SDH (succinate dehydrogenase) by 1.92 folds, FH (fumarate hydratase) by 2.4 foldsand malate synthase (MS) by 1.26 folds and further upregulated after PGPR inoculation. This study demonstrates the importance of PGPR in managing nematode infection in plants through alteration in the synthesis of different secondary metabolites in plants.