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In the last few decades, use of copper oxide nanoparticles (CuO NPs) has been increased significantly that eventually included as a growth stimulator. This makes it essential to examine their impact on several plants. In the study detailed here, we investigated the effects of CuO NPs on the growth, physiological efficiency, biochemical assays, and antioxidant system in the mustard plant. Varying concentrations (0, 2, 4, 8, and 16 mg/L) of CuO NPs were applied at 25 days after sowing (DAS), and sampling took place at 30 and 45 DAS. The results indicate that CuO NPs-treated plants registered an increase in the growth and biomass over their respective control. Among different concentrations of CuO NPs (0, 2, 4, 8, and 16 mg/L), 8 mg/L proved to be the optimum foliar spray treatment and increase the chlorophyll content, net photosynthetic rate, leaf proline content, and antioxidant enzymes activity. We concluded that CuO NPs interact with meristematic cells triggering biochemical pathways conductive to an enhancement of the growth attributes. Further studies are needed to investigate the mechanisms of CuO NPs in mustard.

Copper (Cu) is an essential micronutrient prerequisite for various metabolic processes in plants. At optimum concentration, it performs a vital role in plant growth and development, while as at supra-optimal levels, it disturbs the normal growth in plants. Due to its dual behavior (vital and harmful), the present experiment was designed to assess the potential role of different Cu concentrations (30, 60, and 90) on Brassica juncea cv. Varuna plants. The experiment was set up in a randomized block design, and various physiological, biochemical, microscopic, and histochemical parameters were assessed at 30, 45, and 60 days after sowing. According to our findings, Cu inhibits growth at all concentrations over the control. The maximum reduction was reported in plants cultivated on Cu 90 mg kg−1 of soil. Cu inhibits the chlorophyll content, RUBISCO activity, photosynthetic parameters, PSII activity, electron transport, and maximum quantum yield, at all concentrations. Cu stress decreases nitrate reductase and carbonic anhydrase activity as well as reduction in relative water content and carbohydrate levels in treated plants. Cu levels induced oxidative stress molecules like reactive oxygen species and malondialdehyde content in test plants, due to which the enzymatic antioxidants (catalase, superoxide-dismutase, and peroxidase) as well as non-enzymatic antioxidants (glutathione, proline), were unregulated. Excess Cu level disturbs the essential nutrient and decreases the levels of nitrogen, phosphorus, and potassium while elevated levels of Cu were observed in test plants. From the above findings, we conclude that Cu displayed a toxic effect at all the concentrations and reduced growth, photosynthetic parameters, and biochemical parameters in Brassica juncea.

Nitric oxide (NO) plays a vital role in plant defense against various environmental stresses. However, the study on the defensive effect of NO on the phytotoxicity induced by zinc oxide nanoparticles (ZnO-NPs) remains scarce. In the present study, sodium nitroprusside (SNP, a NO donor) was used to investigate the mechanism of NO in ameliorating the ZnO-NPs toxicity in mustard (Brassica juncea (L.) Czern.) plants. The plants were treated with the different concentrations of SNP (100 µM) and ZnO-NPs (1000 and 2000 µM) either alone or in combination at 25 days after sowing (DAS) for five days consecutively. The results of our study shows that 100 µM of SNP proved highly effective in mitigating the toxicity induced by ZnO-NP. SNP significantly improve chlorophyll content that partially improve photosynthesis in ZnO-NPs stressed plants. Moreover, the defensive role of SNP in relieving the oxidative damage induced by ZnO-NPs is intimately linked to NO-induced antioxidative defense system. The spray of SNP increased the growth biomarkers as well as proline content in control as well as in ZnO-NPs-treated plants. Additionally, microscopic studies further reveal an increase in the size of stomatal aperture on SNP exposure in ZnO-NPs treated plants. Overall, this study provides the first evidence indicating the functions of SNP in alleviating the ZnO-NPs toxicity in mustard plants.

Copper (Cu) is an essential mineral nutrient for the proper growth and development of plants; it is involved in myriad morphological, physiological, and biochemical processes. Copper acts as a cofactor in various enzymes and performs essential roles in photosynthesis, respiration and the electron transport chain, and is a structural component of defense genes. Excess Cu, however, imparts negative effects on plant growth and productivity. Many studies have summarized the adverse effects of excess Cu on germination, growth, photosynthesis, and antioxidant response in agricultural crops. Its inhibitory influence on mineral nutrition, chlorophyll biosynthesis, and antioxidant enzyme activity has been verified. The current review focuses on the availability and uptake of Cu by plants. The toxic effects of excess Cu on seed germination, plant growth and development, photosynthesis, and antioxidant response in plants are discussed. Plant tolerance mechanisms against Cu stress, and management of Cu-contaminated soils are presented.

Glucose (Glc), a monosaccharide, accumulates in plants as a minor product of photosynthesis as well as a breakdown product of sucrose. Glucose regulates various physiological processes in plants; therefore, the present experiment was carried out to assess its role in mustard plants. Seeds of Brassica juncea were sown into pots filled with soil and farmyard manure. Glc treatments were provided as a foliar spray at the 25-day stage of growth for 5 days consecutively. Plants were sampled at the 30, 45 and 60-day stage of growth to assess various biological and biochemical parameters. Glc promoted the growth of plants in the following order of concentration: 30 mM > 20 mM > 40 mM > 10 mM > 50 mM > 0 mM. Glc treatment augmented photosynthetic efficiency by elevating primary photochemistry, stomatal movement and conductance, internal CO2 concentration, transpiration rate, and net photosynthetic rate leading to enhanced synthesis of carbohydrate. A decline in photosynthesis at higher sugar accumulation was prevented by its utilization during respiration. Moreover, the activity of photosynthetic (rubisco and carbonic anhydrase) and respiratory enzymes (hexokinase, succinate dehydrogenase, and fumarase) also increased, which suggests that Glc-mediated growth promotion depends on the dynamics between anabolic and catabolic pathways. Generation of reactive oxygen species, antioxidant enzyme activity, and elemental status, which affect the rate of photosynthesis, were also regulated in Glc-treated plants.

The salt stress limits the production of mustard throughout the world and it is one of the major abiotic stresses. Crop productivity is declining due to the limited area of fertile land. In order to investigate the effects NO donor on salt tolerance and the recovery of Brassica juncea. (L) cv. RGN-48, sodium nitroprusside (SNP) was applied at 1, 10 or 100 µM concentrations as foliar spray for five days consecutively. SNP triggered a significant increase in the main antioxidative enzymes including catalase (CAT), peroxidase (POX) and superoxide dismutase (SOD) along with the increase in the enzymes involved in nitrogen metabolism (nitrate reductase), photosynthesis and respiration (carbonic anhydrase, rubisco, fumarase, hexokinase and succinate dehydrogenase). On the other hand, decrease in programmed cell death (PCD) and the contents of hydrogen peroxide (H2O2), superoxide anion (O2.−) and malondialdehyde (MDA) was observed in NaCl-stressed plants subjected to the different concentrations of SNP. Consequently, the spray of SNP restored several photosynthetic attributes i.e. SPAD chlorophyll, chlorophyll fluorescence and gas exchange parameters in NaCl-stressed plants. These results suggested that exogenous application of SNP is useful in ameliorating the toxicity generated by NaCl in mustard plants.

Auxins (Aux) are primary growth regulators that regulate almost every aspect of growth and development in plants. It plays a vital role in various plant processes besides controlling the key aspects of cell division, cell expansion, and cell differentiation. Considering the significance of Aux, and its potential applications, a study was conducted to observe the impact of indole acetic acid (IAA), a most active and abundant form of Aux on Brassica juncea plants growing under natural environmental conditions. Different concentrations (0, 10−10, 10−8, 10−6 M) of IAA were applied once in a day at 25-day stage of growth for 5 days, consecutively. Various parameters (growth, photosynthetic, biochemical, oxidative biomarkers and nutrient composition) were assessed at different days after sowing (DAS). Scanning electron microscopy (SEM) of leaf stomata, reactive oxygen species (ROS) localization in leaf and roots, and confocal microscopy were also conducted. The results revealed that all the IAA concentrations were effective in growth promotion and ROS reduction, however, the 10−8 M of IAA exhibited the maximum improvement in all the above mentioned parameters as compared to the control.

It is known that auxin and nitric oxide have the ability to ameliorate various abiotic stresses in plants individually. However, their interactive effects on the stress generated by salt in plants are not reported yet. Therefore, the present study was conducted to explore the effectiveness of sodium nitroprusside (SNP), a donor of nitric oxide and IAA (Indole acetic acid) individually and in combination on the photosynthetic efficiency, antioxidative enzyme activities, and plant biomass under salt stress. Twenty-five-day-old plants were exposed to SNP and IAA individually and in combination for 5 days continuously, and it was found that both SNP and IAA showed almost similar response at 30 and 45 days of old plants and increased studied parameters over their respective controls. However, the interactive effect of both SNP and IAA excelled over the individual response of SNP and IAA. On the other hand, the presence of salt in soil significantly decreased the parameters studied. Furthermore, stress generated by NaCl was overcome by the exogenous application of SNP, IAA alone as well as in combination at both the stages of samplings. However, the combination of IAA and SNP was more effective at 45 DAS where the value of plant biomass and photosynthetic efficiency was more in comparison to control plants. The level of antioxidant enzymes and proline was further enhanced by SNP and IAA and maximum values were reported in the plants received both SNP and IAA under NaCl stress. This enhanced antioxidant system and proline accumulation could ameliorate the stress induced by NaCl in plants that was reflected by the improved plant biomass, and photosynthetic efficiency in comparison to control plants.

Flavonoids are a special category of hydroxylated phenolic compounds having an aromatic ring structure. Among several subclasses of flavonoids, the flavonol subclass contains a special compound – quercetin. Quercetin is a bioactive natural compound built upon the flavon structure, i.e., C6(ring A)-C3(ring C)-C6(ring B). It facilitates several plant physiological processes such as seed germination, pollen growth, antioxidant machinery, and photosynthesis, as well as induces proper plant growth and development. Quercetin is a powerful antioxidant, so it potently provides plant tolerance against several biotic and abiotic stresses. This review highlights the role of quercetin in increasing several physiological and biochemical processes in under stress and non-stress environments. Additionally, this review briefly assesses the role of quercetin in mitigating biotic and abiotic stresses, e.g., salt, heavy metal, and UV stress. Furthermore, the biosynthesis of flavonoids along with fresh advances and regulation in its signaling pathway, as well as the role of quercetin in plant signaling is also discussed.

Lipoxygenases (LOXs), naturally occurring enzymes, are widely distributed in plants and animals. LOXs can be non-sulfur iron, non-heme iron, or manganese-containing dioxygenase redox enzymes. LOXs catalyze the oxidation of polyunsaturated fatty acids into fatty acid hydroperoxides. Linolenic acid, a precursor in the jasmonic acid (JA) biosynthesis, is converted to 12-oxo-phytodienoic acid through oxygenation with LOX, allene oxide synthase, and allene oxide cyclase. Moreover, JA participates in seed germination, fruit ripening, senescence, and many other physio-biochemical processes. LOXs also play crucial roles in defense responses against biotic stress, i.e., insects, pests, pathogenic attacks, and abiotic stress, such as wounding, UV-rays, extreme temperature, oxidative stress, and drought.

Melatonin (MEL) is an antioxidant molecule, present throughout plant kingdom, animals, and microbes. It is a well-known free radical scavenger and modulates growth and development in plants against various abiotic and biotic stresses. The present study was done to investigate the role of MEL as a foliar spray on the morphological, physiological, and biochemical parameters in Brassica juncea cv. Varuna. Five different doses (10, 20, 30, 40, or 50 μM) of MEL were applied as foliar spray to the leaf of plant at 25 days after sowing (DAS) and continued up to 30 DAS once in a day. The plants were sampled at 30, 45, and 60 DAS to assess various parameters. The present results indicate that most of the parameters, i.e., growth, photosynthetic, nutrients, and enzyme activities increased in a concentration dependent manner. MEL application reduced the accumulation of reactive oxygen species (ROS) by enhancing the antioxidant enzyme activities. Microscopic examinations further revealed a significant increase in the size of the stomatal aperture in the presence of MEL. Out of the various concentrations tested, 40 μM of MEL proved best and can be used for further studies.

Nitric oxide (NO) acts as a gaseous diffusible plant growth regulator. It plays an important role in growth and development of plants. Therefore, in present study mustard plants were sprayed with different concentrations of sodium nitroprusside (0, 10–4 M, 10–5 M and 10–6 M), a donor of NO, at 25 days after sowing to assess different physiological parameters. The results indicate that foliar spray of SNP upregulate chlorophyll content, chlorophyll fluorescence along with gaseous exchange parameters which further boost overall photosynthetic efficiency. A gradual increase in carbon metabolism (total reducing sugars, total carbohydrate content, glucose, fructose, sucrose and starch content) was also observed in SNP-treated plants as compared to control. Nutrient status (carbon, nitrogen, phosphorus, sulfur, potassium and magnesium) of leaves also shows a significant increase. The activity of various enzymes associated with nitrogen metabolism, CO2/HCO3− homeostasis, glycolysis, Calvin cycle and Krebs cycle (nitrate reductase, carbonic anhydrase, hexokinase, rubisco, fumarase and succinate dehydrogenase) were also increased in the presence of SNP. It was also reported that O2−, H2O2 and MDA were decreased in SNP-treated samples. SNP application also upregulate antioxidative defense system by increasing the activity of antioxidant enzymes, i.e., CAT, POX and SOD. Thus, it can be concluded from the present observation that SNP proved beneficial and alter most of the parameters which ultimately improve photosynthetic efficiency in mustard plants.

Plant hormones play important roles in controlling how plants grow and develop. While metabolism provides the energy needed for plant survival, hormones regulate the pace of plant growth. Strigolactones (SLs) were recently defined as new phytohormones that regulate plant metabolism and, in turn, plant growth and development. This group of phytohormones is derived from carotenoids and has been implicated in a wide range of physiological functions including regulation of plant architecture (inhibition of bud outgrowth and shoot branching), photomorphogenesis, seed germination, nodulation, and physiological reactions to abiotic factors. SLs also induce hyphal branching in germinating spores of arbuscular mycorrhizal fungi (AMF), a process that is important for initiating the connection between host plant roots and AMF. This review outlines the physiological roles of SLs and discusses the significance of interactions between SLs and other phytohormones to plant metabolic responses.

Nanotechnology now plays a revolutionary role in many applications; nanomaterials have experienced significant importance in both basic and applied sciences as well as in bio-nanotechnology. Zinc oxide nanoparticles (ZnO-NPs) have become one of the most important metal oxide NPs in biological applications due to their beneficial impacts. The purpose of this study was to explore the effects of ZnO-NPs in reducing Cd toxicity by studying the growth, photosynthesis reactions, antioxidant system, oxidative stress, and protein content in Lycopersicon esculentum (tomato). ZnO-NPs induced an upregulation of antioxidative enzymes which protect the photosynthetic apparatus in plants. Seeds of tomato were sown to create nursery. At 20 days after sowing (DAS), seedlings were transferred to soil pots. Varied concentrations (0.4, 0.6 or 0.8 mM) of Cd were applied to the soil after 24 and 25 DAS. Zinc (Zn; 50 mg/L) and ZnO-NPs (50 mg/L) treatments were given continuously for 5 days from 31 to 35 DAS and sampling took place at 45 DAS. The results indicate that a Cd-generated oxidative burst in the form of elevated hydrogen peroxide (H2O2) levels resulted in a decline in cell viability through enhanced activity of the antioxidant system and proline content; the data increased on follow-up treatment with ZnO-NPs. Foliar application of ZnO-NPs significantly enhanced plant height, fresh, and dry weight of plant, leaf area, SPAD chlorophyll, photosynthetic attributes, i.e., net photosynthetic rate (PN), transpiration rate (E), internal CO2 concentration (Ci), and stomatal conductance (gs). Application of ZnO-NPs reduced the adverse effects generated by Cd and increased protein content, activities of nitrate reductase and carbonic anhydrase over the control in both stressed and non-stressed plants. Additionally, microscopic studies showed a marked increase in stomatal aperture after ZnO-NPs treatment in the presence or absence of Cd. This was associated with decrease in malondialdehyde and superoxide radical (O2−) levels. The present study suggests that ZnO-NPs can be effectively used to reduce the toxicity of Cd in tomato plants and may also be suitable for testing on other crop species.

The objective of the study was to explore the effect of zinc oxide nanoparticles (ZnO-NPs) through root treatment on growth biomarkers, photosynthetic traits, activities of carbonic anhydrase and various antioxidant enzymes as well as the yield of tomato plants. 20 days old seedlings of tomato (cv. PKM-1) were dipped in double distilled water (control), 10, 50, 100 or 200 ppm of ZnO-NPs for 15, 30 or 45 min, respectively. At the stage of 45 and 60 days after sowing (DAS), the plants developed from ZnO-NPs (10 ppm for 30 min) showed improved growth and photosynthetic attributes, enhanced activity of various antioxidant enzymes (e.g., catalase, peroxidase and superoxide dismutase) and higher accumulation of proline and protein content over the non-treated plant. The fruits number and yield in ZnO-NPs treated plants (10 ppm; 30 min) were higher whereas ascorbic acid was lower than the non-treated plant. These fruits possessed higher levels of β-carotene and lycopene content. The root dipping with 10 ppm for 30 min of ZnO-NPs was found to be best for most of the evaluated parameters.

Flavonoids are a special category of hydroxylated phenolic compounds having an aromatic ring structure. Quercetin is a special subclass of flavonoid. It is a bioactive natural compound built upon the flavon structure nC6(ring A)-C3(ring C)-C6(ring B). Quercetin facilitates several plant physiological processes, such as seed germination, pollen growth, antioxidant machinery, and photosynthesis, as well as induces proper plant growth and development. Quercetin is a powerful antioxidant, so it potently provides plant tolerance against several biotic and abiotic stresses. This review highlights quercetin’s role in increasing several physiological and biochemical processes in under stress and non-stress environments. Additionally, this review briefly assesses quercetin’s role in mitigating biotic and abiotic stresses (e.g., salt, heavy metal, and UV stress). The biosynthesis of flavonoids, their signaling pathways, and quercetin’s role in plant signaling are also discussed.

24-epibrassinolide (EBL) and iron (Fe) individually are well recognized for their significant role in various biological functions of plants but their interactive effect on iron transport, stress biomarkers, photosynthetic and biochemical parameters in Brassica juncea is poorly investigated. Therefore, this study was conducted to reveal the effect of Fe in the presence of 24-epibrassinolide (EBL), an analogue of brassinosteroids (BRs) on Brassica juncea plants. Fe in the form Fe-EDTA (1, 5 or 50 µM) was supplied with nutrient solution for 5 days followed by the foliar spray with deionised water (control) or EBL (0.01 µM) on 16-day-old plants for 5 days. Plant samples of 30-day-old plants were collected for the assessment of growth and photosynthetic performance and antioxidant parameters. Results clearly indicated that Fe altered plant metabolism. Lower concentration of Fe (5 µM) increased the growth biomarkers, SPAD (soil plant analysis development) chlorophyll level and photosynthetic rate, whereas higher concentration of Fe (50 µM) proved toxic to Brassica juncea and showed reduced growth, biomass of plant, SPAD chlorophyll level, and photosynthetic traits. However, the application of EBL to Fe-stressed plants reversed the deleterious effects caused by the Fe (50 µM) by improving the activities of antioxidant enzymes and increasing the proline accumulation in plant cells that are reflected in increased plant growth and other physiological parameters. It is concluded that lower concentration of Fe could be exploited as micronutrients whereas combined application of Fe with EBL acts as a stress alleviator for the toxic effects caused by Fe alone.

Jasmonic acid (JA) and its methyl ester, methyl jasmonates (MeJAs), is categorized under phytohormones. It is ubiquitously found all over the plant kingdom but varies in concentration from species to species. Chemically, it is known as derivatives of the fatty acid metabolism. JAs are synthesized from α-linolenic acid (α-LeA/18:3) via the octadecanoid pathway. JAs attached to its receptor, CORONATINE INSENSITIVE1 (COI1) triggers the signaling cascade and enables the expression of genes and generate various responses under stress and stress-free conditions. Moreover, JAs are known to regulate a wide range of physiological processes in plants such as plant growth, reproductive development and senescence. It also induces plant defense responses against various biotic stresses such as herbivore attack or pathogen infection. In this chapter, a summary of recent advances in our understanding of JA synthesis and signaling along with its role in regulating physiology of plant in presence or absence of biotic stress.

Silicon (Si) is the second most abundant element present on the lithosphere and a quasi-essential element for plants' cellular and developmental processes. Si is associated with augmented germination, growth, photosynthesis, gas exchange, photosystem efficiency, and yield attributes in unstressed and stressed plants. The exogenous application of Si facilitates morpho-physiological and biochemical traits. It triggers the content of compatible osmolyte and enzymatic and non-enzymatic antioxidants, which decreases reactive oxygen species like hydrogen peroxide and superoxide. Uptake and transport of Si in plants are discussed in this review. Furthermore, the potent roles of Si in plants are emphasized. The cross-talk of Si with phytohormones such as auxins, cytokinins, gibberellins, abscisic acid, brassinosteroids, salicylic acid, nitric oxide, jasmonic acid, and ethylene is also presented. Moreover, attempts have been made to cover the contribution of Si mediated enhancement in 'omics' (genomic, transcriptomic, proteomic, metabolomic, and ionomic) approach that is useful in diminishing stress. This review aims to provide Si integration with phytohormone and utilization of 'omic approaches' to understand the role of Si in plants. This review also underlines the need for future research to evaluate the role of Si during abiotic stress in plants and the identification of gaps in understanding this process as a whole at a broader level.

Glucose is recognized as signaling molecule that regulates growth and development of plants under various environmental cues, but their effect in regulation of copper induced toxicity in plants is not yet investigated. This study revealed the effect of exogenously sourced glucose on Cucumber plants exposed to increasing concentration of copper. Glucose mediated response on growth performance, photosynthetic efficiency, antioxidant enzymes, oxidative stress markers, ion uptake were analyzed in the presence and absence of copper. Glucose alone and in combination with lower concentration of copper improved the growth, photosynthetic performance, and antioxidant capacity of cucumber plants. However, higher concentrations of copper alone showed oxidative damage through increased electrolyte leakage, H2O2 accumulation, lipid peroxidation and reduced uptake of macronutrients. Application of glucose to copper-stressed plants enhanced activities of Rubisco, antioxidant enzymes, proline accumulation and maintained copper level in aerial parts of plants. These enhanced activities of antioxidant enzymes, proline accumulation, uptake of NPK and maintained equilibrium of copper in plants, leading to detoxification of copper stress in cucumber plants. This study provides an understanding that exogenous application of glucose can be employed as vital biochemical approach in alleviating copper-induced toxicity and could be utilized as phytoremediation technique for removal of excess transition metal from polluted soil.

In plants, glucose (Glc) acts as a crucial signaling molecule in mediating metabolism, growth, stress tolerance mechanism, etc. However, little is known about Glc supplementation in salinity tolerance. This experiment was designed to study the ameliorative effect of Glc in mustard under salt stress. The seeds were soaked in three concentrations of NaCl (0, 50, or 100 mM) for 8 h and then treated with four concentrations of Glc (0, 2, 4, or 8%) as foliar spray for 5 days at 25-day stage. The plants were harvested at three growth stages (30, 45, and 60) for examining morpho-physiological and proteomic studies. Glc application as foliar spray increases growth, photosynthesis, and antioxidative enzyme activities in NaCl-treated plants. Glc applied in plants also showed reduction in superoxide anion, hydrogen peroxide, and malondialdehyde content under salt stress. Amongst all doses of Glc, spray of 4% Glc proved best in alleviating the harmful effects of salinity.

Hydrogen sulfide (H2S) is a gasotransmitter and signaling molecule associated with seed germination, plant growth, organogenesis, photosynthesis, stomatal conductance, senescence, and post-harvesting. H2S is produced in plants via both enzymatic and non-enzymatic pathways in different subcellular compartments. Exogenous application of H2S facilitates versatile metabolic processes and antioxidant machinery in plants under normal and environmental stresses. This compound interacts with phytohormones like auxins, abscisic acid, gibberellins, ethylene, jasmonic acid, and salicylic acid. Furthermore, H2S participates in signal transductions of other signaling molecules like nitric oxide, carbon monoxide, calcium, methylglyoxal, and hydrogen peroxide. It also mediates post-translational modification, which is a protective mechanism against oxidative damage of proteins. This review summarizes the roles of H2S as intriguing molecule in plants.

Salinity is one of the major threats to sustainable agriculture that globally decreases plant production by impairing various physiological, biochemical, and molecular function. In particular, salinity hampers germination, growth, photosynthesis, transpiration, and stomatal conductance. Salinity decreases leaf water potential and turgor pressure and generates osmotic stress. Salinity enhances reactive oxygen species (ROS) content in the plant cell as a result of ion toxicity and disturbs ion homeostasis. Thus, it imbalances nutrient uptake, disintegrates membrane, and various ultrastructure. Consequently, salinity leads to osmotic and ionic stress. Plants respond to salinity by modulating various morpho-physiological, anatomical, and biochemical traits by regulating ion homeostasis and compartmentalization, antioxidant machinery, and biosynthesis of osmoprotectants and phytohormones, i. e, auxins, abscisic acid, brassinosteroids, cytokinins, ethylene, gibberellins, salicylic acid, jasmonic acid, and polyamines. Thus, this further modulates plant osmoticum, decreases ion toxicity, and scavenges ROS. Plants upregulate various genes and proteins that participate in salinity tolerance. They also promote the production of various phytohormones and metabolites that mitigate the toxic effect of salinity. Based on recent papers, the deleterious effect of salinity on plant physiology is discussed. Furthermore, it evaluates the physiological and biochemical responses of the plant to salinity along with phytohormone response. This review paper also highlights omics (genomics, transcriptomics, proteomics, and metabolomics) approach to understand salt stress tolerance.

Auxins (Aux) are primary growth regulators that regulate almost every aspect of growth and development in plants. It plays a vital role in various plant processes besides controlling the key aspects of cell division, cell expansion, and cell differentiation. Considering the significance of Aux, and its potential applications, a study was conducted to observe the impact of indole acetic acid (IAA), a most active and abundant form of Aux on Brassica juncea plants growing under natural environmental conditions. Different concentrations (0, 10(−10), 10(−8), 10(−6) M) of IAA were applied once in a day at 25-day stage of growth for 5 days, consecutively. Various parameters (growth, photosynthetic, biochemical, oxidative biomarkers and nutrient composition) were assessed at different days after sowing (DAS). Scanning electron microscopy (SEM) of leaf stomata, reactive oxygen species (ROS) localization in leaf and roots, and confocal microscopy were also conducted. The results revealed that all the IAA concentrations were effective in growth promotion and ROS reduction, however, the 10(−8) M of IAA exhibited the maximum improvement in all the above mentioned parameters as compared to the control.

Melatonin is an endogenous indolamine found in many plants. It has been shown to generate a wide range of metabolic, physiological, and cellular responses, thus affecting growth and development, particularly under different environmental stresses. In the present review, we focus on its role in germination, growth and development, photosynthesis, senescence, and antioxidant activity in plants. Further, an effort has been made to discuss its occurrence, biosynthesis, and relationship with other phytohormones in plants. Moreover, melatonin-mediated signaling and its mechanisms of action under stress conditions in plants have been comprehensively discussed. Finally, its role under various abiotic stress conditions has also been discussed in this review.

Phytoremediation is an ecologically and economically feasible technique to remove heavy metal from soil. The aim of the study was to examine cadmium (Cd) toxicity and phytoremediation aptitude of Brassica juncea. In the present study, plants survived when exposed to different levels of Cd (0, 25, 50 and 100 mg/kg soil) and accumulated a large amount of Cd in its root and shoot. Translocation factor (TF) of Cd from root to shoot was > 1 at both 45 and 60‐day stage of growth suggesting that B. juncea is a hyperaccumulator and strong candidate for phytoextraction of Cd. Alongside, Cd impaired photolysis of water, PSII activity, nutrient uptake, photosynthesis and sugar accumulation in the plant. Cd-generated oxidative stress restricts the growth of B. juncea. The toxic effect of Cd was more pronounced at 45‐day stage of growth signifying the drifting of plant towards acquirement of exclusion strategy.

Heavy metal pollution is one of the serious environmental problems, damaging all living organisms globally. Cadmium (Cd) is a nonessential, deadly toxic metal that has a harmful effect on plants. Entry of Cd inside the plant body causes an abiotic stress and provokes the plant to generate anti-stress agents, such as sodium dismutase, catalase, guaiacol peroxidase, and glutathione. Cadmium accumulates in plants and hinders their normal productivity. The accumulation depends on Cd entry in plants via roots, translocation via xylem and phloem, and through different processes, channels, and metal transporter. Even a very small dose of Cd influences the physio-biochemical parameters of the plant. Cadmium stress reduces the efficiency of plants by modulating their morphology, physiology, and biochemistry. This chapter underlines transport, mechanism of action, and regulatory network of Cd, and harmful aspects of Cd exposure to plants. The chapter also discusses the Cd effect on seed germination, growth, development, chlorophyll content, photosystem and photosynthesis, carbon assimilation, and reproduction.

Nanotechnology is among the most innovative fields of twenty-first century. Nanoparticles (NPs) are organic or inorganic materials having sizes ranging from 1 to 100 nm; in recent years NPs have come into extensive use worldwide. The dramatic increase in use of NPs in numerous applications has greatly increased the likelihood of their release to the environment. Zinc oxide nanoparticles (ZnO-NPs) are considered a ‘biosafe material’ for organisms. Earlier studies have demonstrated the potential of ZnO-NPs for stimulation of seed germination and plant growth as well as disease suppression and plant protection by virtue of their antimicrobial activity. Both positive and negative effects of ZnO NPs on plant growth and metabolism at various developmental periods have been documented. Uptake, translocation and accumulation of ZnO-NPs by plants depend upon the distinct features of the NPs as well as on the physiology of the host plant. This review will contribute to current understanding the fate and behavior of ZnO-NPs in plants, their uptake, translocation and impacts on mitigating several negative plant growth conditions.

Silicon (Si) and 24-Epibrassinolide (EBL) were exogenously applied to assess the photosynthetic efficiency in Brassica juncea under salt stress and to correlate it with the antioxidant system. Seeds of B. juncea were sown in pots and supplemented with NaCl at 15-day stage. Si and EBL treatments were given at 20 and 25-day stage, respectively. Net photosynthetic rate and stomatal conductance reduced significantly in the presence of NaCl. The spray of Si and EBL alone or in combination significantly increased the growth and photosynthetic traits in the presence/absence of NaCl stress. The antioxidant activity (catalase, peroxidase and superoxide dismutase) and proline content got enhanced by salt stress which was further enhanced upon follow-up treatment with 24-epibrassinolide and silicon alone or in combination. A combined effect of Si and EBL counters the damaged caused by the salt stress.

BRs are polyhydroxylated sterol derivatives, classified as phytohormones. Plants of Brassica juncea var. Varuna were grown in pots and an aqueous solution (10−8 M) of two brassinosteroid isomers 28-homobrassinolide (HBL) and 24-epibrassinolide (EBL) of same concentration (10−8 M) was applied to their leaves. The treatment up-regulated the photosynthetic machinery directly by enhancing water splitting activity, photochemical quenching, non-photochemical quenching, maximum PSII efficiency, actual PSII efficiency, electron transport rate, stomatal movement, stomatal conductance, internal CO2 concentration, transpiration rate, net photosynthetic rate and carbohydrate synthesis. Moreover, the level of biochemical enzymes (carbonic anhydrase and nitrate reductase), reactive oxygen species (superoxide and hydrogen peroxide) generation, antioxidant enzyme activity and mineral status (C, N, Mg, P, S, K), which indirectly influence the rate of photosynthesis, also improved in the treated plants. Out of the two BR analogues tested, EBL excelled in its effects over HBL.

The present experiment was conducted to investigate the promotive effects of exogenous glucose (Glc) on the morpho-physiology in Brassica juncea. L. cv. RGN-48. The plants were treated with the different concentrations (0, 2, 4, and 8%) of glucose as foliar spray at 25 days after sowing (DAS) for 5 days consecutively. The plants were collected to analyze various growth and photosynthetic parameters at 30, 45, and 60 DAS. After 5 days exposure to Glc, the level of carbohydrate, total reducing sugars, proline, plant water status, chlorophyll content, as well as that of activities of peroxidase (EC 1.11.1.7), catalase (EC 1.11.1.6), and superoxide dismutase (EC 1.15.1.1) were increased. Glc application also enhanced the gaseous exchange parameters, i.e., stomatal conductance (gs), internal CO2 concentration (Ci), transpiration rate (E), and net photosynthetic rate (PN) in intact leaf. Other enzymes, such as nitrate reductase (EC 1.7.99.4) and carbonic anhydrase (EC 4.2.1.1) were also increased. Additionally, microscopic studies further reveal a remarkable increase in the stomatal aperture on Glc exposure. Moreover, exogenous Glc decreases the levels of malondialdehyde (MDA), superoxide radical (O2·−) and hydrogen peroxide (H2O2). This indicates that exogenous Glc application has a positive effect on Brassica juncea plants.

Nitric oxide (NO) is a major signaling biomolecule associated with signal transduction in plants. The beneficial role of NO in plants, exposed to several abiotic stresses shifted our understanding as it being not only free radical, released from the toxic byproducts of oxidative metabolism but also helps in plant sustenance. An explosion of research in plant NO biology during the last two decades has revealed that NO is a key signal associated with plant growth, germination, photosynthesis, leaf senescence, pollen growth and reorientation. NO is beneficial as well as harmful to plants in a dose-dependent manner. Exogenous application of NO at lower concentrations promotes seed germination, hypocotyl elongation, pollen development, flowering and delays senescence but at higher concentrations it causes nitrosative damage to plants. However, this review concentrates on the beneficial impact of NO in lower concentrations in the plants and also highlights the NO crosstalk of NO with other plant hormones, such as auxins, gibberellins, abscisic acid, cytokinins, ethylene, salicylic acid and jasmonic acid, under diverse stresses. While concentrating on the multidimensional role of NO, an attempt has been made to cover the role of NO-mediated genes associated with plant developmental processes, metal uptake, and plant defense responses as well as stress-related genes. More recently, several NO-mediated post translational modifications, such as S-nitrosylation, N-end rule pathway operates under hypoxia and tyrosine nitration also occurs to modulate plant physiology.

Phytocannabinoids are a structurally diverse class of bioactive naturally occurring compounds found in angiosperms, fungi, and liverworts and produced in several plant organs such as the flower and glandular trichrome of Cannabis sativa, the scales in Rhododendron, and oil bodies of liverworts such as Radula species; they show a diverse role in humans and plants. Moreover, phytocannabinoids are prenylated polyketides, i.e., terpenophenolics, which are derived from isoprenoid and fatty acid precursors. Additionally, targeted productions of active phytocannabinoids have beneficial properties via the genes involved and their expression in a heterologous host. Bioactive compounds show a remarkable non-hallucinogenic biological property that is determined by the variable nature of the side chain and prenyl group defined by the enzymes involved in their biosynthesis. Phytocannabinoids possess therapeutic, antibacterial, and antimicrobial properties; thus, they are used in treating several human diseases. This review gives the latest knowledge on their role in the amelioration of abiotic (heat, cold, and radiation) stress in plants. It also aims to provide synthetic and biotechnological approaches based on combinatorial biochemical and protein engineering to synthesize phytocannabinoids with enhanced properties.

The present study was carried out to screen out the best concentration of proline, applied exogenously as foliar spray, which will have beneficial effects on growth and physio-biochemical parameters in two varieties of Brassica juncea (‘Varuna’ and ‘RH-30’). The proline concentrations tested in this experiment were 0, 10, 20 or 30 mM. The foliar spray was done at 29 days after sowing (DAS) and sampling at 60 DAS. Out of these concentrations, 20 mM proline was found best. The proline treatment significantly increased the growth, net photosynthetic rate and related attributes, SPAD value of chlorophyll, leaf carbonic anhydrase activity and quantum yield of photosystem II, as well as proline content and activity of antioxident enzymes also increased in both the varieties at 60 d stage of growth. The result was more pronounced in the ‘Varuna’ than in ‘RH-30’.

The present investigation was conducted to evaluate the silicon (Si) mediated responses in different cultivars of Indian mustard (Brassica juncea) and to evaluate if Si could be used as an essential, beneficial, or quasi-essential element for growth and development of these cultivars. Surface sterilized seeds were sown in pots and allowed to germinate under natural environmental conditions. At 10, 12, 14, 16, and 18 days after germination, a range of Si concentrations (0.0, 0.2, 0.4, 0.8 and 1.6 mM) was administered to the soil and at 30 days post germination the plants were sampled to assess growth and development, leaf gas exchange traits and plant biochemical parameters, including activities of carbonic anhydrase, catalase, peroxidase, superoxide dismutase, and protein and proline content. The results demonstrate a dual response to Si concentration: 0.8 mM of Si significantly increased plant growth and development (length of root and shoot, fresh and dry biomass, and leaf area) and photosynthetic efficiency, and enhanced the antioxidant response in T-59 over all the other cultivars tested, whereas, 1.6 mM of Si significantly reduced the above parameters. It is therefore concluded that low levels of Si could be used as a quasi-essential element for enhanced photosynthetic efficiency and antioxidant response ofBrassica junceaplants; however, the response is cultivar specific and concentration dependent.

The effects of foliar application of proline (20 mM) on growth, physio-biochemical, and yield parameters were assessed in two Brassica juncea (L.) Czern & Coss cultivars, namely, Varuna and RH-30, at different levels (2.8, 4.2, or 5.6 dsm(-1)) of NaCl in soil. At 29 days after sowing (DAS), plants were sprayed with either 20 mM proline or water in the presence or absence of NaCl stress. The NaCl negatively affected parameters related to growth, photosynthesis, and yield in both varieties but more in RH-30 than in Varuna. Exogenous application of proline counteracted the effects of salt stress in Varuna only, by increasing the antioxidative capacity of the plants. Moreover, proline was not effective in alleviating the detrimental effects of higher salt concentrations on the studied parameters. Proline application to unstressed plants increased growth, photosynthesis, and yield parameters in both varieties; however, the effects were more prominent in Varuna than in RH-30.

Plant hormones play a vital role in promoting growth, development and metabolism of the plant, as well as act as a protector against various environmental stresses. In particular, salicylic acid (SA) is a potent phenolic signaling biomolecule and a multifaceted plant growth regulator which participates in a wide range of growth, metabolism and defense systems. Exogenous application of SA facilitates seed germination, growth, and flowering, up-regulates photosynthesis and increases the activity of enzymatic and non-enzymatic antioxidants. SA is a potent tool for sustainably mitigating environmental stresses in many plants by modulating physiological and metabolic processes of plants. Based on recent reports, SA biosynthesis and its regulation are discussed. This review highlights oxidative post-translational modifications, involvement of various proteins, and ROS interaction during SA signaling. Furthermore, it evaluates the role of exogenous application of SA in regulating diverse physiological and biochemical processes in healthy and stressed plants and assesses SA effects in plants exposed to various abiotic stress. Additionally, the cross talk of SA with other phytohormones and polyamines under normal and stressed conditions is also discussed.

Sugars are metabolic substrates playing a part in modulating various processes in plants during different phases of development. Thus, modulating the sugar metabolism can have intense effects on the plant metabolism. Glucose is a soluble sugar, found throughout the plant kingdom. Apart from being a universal carbon source, glucose also operates as a signaling molecule modulating various metabolic processes in plants. From germination to senescence, wide range of processes in plants is regulated by glucose. The effect of glucose is found to be concentration dependent. Photosynthesis and its related attributes, respiration and nitrogen metabolism are influenced by glucose application. Endogenous content of glucose increases upon exposure of plant to various abiotic stresses and also when glucose is supplied exogenously. Glucose accumulation alleviates the damaging effects of stress by enhancing production of antioxidants and compounds similar to that of photosynthetic CO2 fixation which act as an osmoticum by maintaining osmotic pressure inside the cell, pH homeostasis regulator and reduce membrane permeability during stress. Glucose interaction with various phytohormones has also been discussed in this review.

Soil salinity is one of the major abiotic stress factors that hampers plant growth and productivity by limiting photosynthesis and other related metabolic processes. In this study we investigated whether treatment with proline and/or 24-epibrassinolide (EBL) to two contrasting cultivars of Brassica juncea (L.) Czern and Coss viz. Varuna and RH-30 could counteract with the adverse effects of salinity on photosynthesis and seed yield. Plants were treated with proline and/or 24-epibrassinolide (EBL) at 28 and 29d-stages of growth. Salt stress reduced plant growth, photosynthetic attributes, efficiency of PSII (Fv/Fm), leaf water potential and finally seed yield, at harvest but improved the activity of antioxidant enzymes in both the cultivars in a concentration dependent manner. Exogenous application of EBL with proline completely neutralised the adverse effects of salt at 78 mM or 117 mM stress levels whereas the treatment partially neutralised the impact of highest salt concentration of 156 mM, through the upregulation of the antioxidant system.

The present study was designed with an objective to elucidate the effect of the exogenous application of 10-5 M of salicylic acid (SA) to the foliage of the chickpea plants exposed to 0, 25, 50 or 100 mg cadmium (Cd) per kg of soil. The foliage of the plants grown in soil amended with varying doses of Cd was sprayed with 10-5 M of SA at 30 days after sowing (DAS). The plant samples were collected at 60 and 90 DAS to assess various parameters. The damage caused due to the Cd exposure was partially overcome by the exogenous application of SA. The SA treatment resulted in a significant increase of growth, photosynthesis, yield and the activity of antioxidative enzymes viz. catalase, peroxidase and superoxide dismutase in the plants exposed to 0, 25 or 50 mg Cd per kg of soil. However, the treatment did not prove to be fruitful in alleviating completely the stress generated by 100 mg Cd per kg of soil.

Cadmium, a non-essential and toxic metal, negatively affects plant growth and productivity, and alters the plant’s physiological processes necessary for its survival. The present study was designed to explore the individual and combined effects of calcium and salicylic acid (SA) on the morphology and physiology of Brassica juncea L. cv. Varuna under cadmium stress. The application of calcium (2 mM) through the soil and/or SA (10-5 M) as foliar spray enhanced the growth, photosynthetic parameters, and proline content determined after 45 days of treatment. The application of cadmium (6 mg kg-1) through the soil was toxic and decreased both growth and the photosynthetic parameters. The application of calcium and SA in combination was most effective in alleviating the harmful effects of cadmium on growth and photosynthesis. Calcium and SA clearly induced plant protection mechanisms by enhancing proline and chlorophyll accumulation in the leaves.

This study examines the impact of 28-homobrassinolide (HBL) in alleviating the effects of cadmium (Cd) and salinity (NaCl) on wheat plants solely and against the synergy. The surface sterilized seeds of Triticum aestivum cv. PBW-373 were sown in the soil amended either with salinity or cadmium or both. The foliage in was sprayed at 20d after sowing (DAS) both in stressed and non-stressed plants. The spray of HBL at 20 DAS increased almost all the parameters while decreased the H2O2 content and lipid peroxidation in the leaves. The presence of cadmium and/or salinity decreased the values for all the growth and photosynthetic parameters but improved the activity of antioxidant enzymes and proline content in 30d old plants. However, the ill effects observed under NaCl and/or Cd treatment were completely overcomed by the spray of HBL to the plants at 20d stage. The spray of HBL to stressed plants further increased the antioxidant enzyme activities and proline content thereby giving tolerance to the plants against the stress.

Tomato (Solanum lycopersicum L.) is moderately salt sensitive and yield can be reduced by 50% when exposed to a 7.5 dS·m−1 electrical conductivity (EC) saline solution. The response of tomato, cv. K-21, to presowing seed treatment with sodium chloride (NaCl) and sodium nitroprusside (SNP) was investigated. Before sowing, surface-sterilized seed of tomato were soaked in 50, 100, or 150 mM NaCl for 8 h and then transferred to a 10−5 M solution of SNP for 8 h. Plants were sampled at 45 and 60 days after sowing (DAS) to assess carbonic anhydrase activity (E.C. 4.2.1.1), relative water content, photosynthetic attributes, and growth parameters. Activity of carbonic anhydrase and all other parameters was increased by SNP application following the NaCl treatment. Detrimental effects generated by the 50 mM NaCl concentration were completely neutralized by SNP at 60 DAS, whereas those of highest NaCl concentration were not reversed by SNP at both sampling stages. It appears that SNP alleviates salinity stress up to...

The aim of this study was to determine the effect of salicylic acid (SA) on nitrogen fixation and assimilation under conditions of cadmium stress in chickpea plants. Chickpea seeds were sown in pots containing 0, 25, 50, or 100 mg of cadmium per kilogram of soil. The foliage of the 30-day-old plants was sprayed with 10−5 M SA, and the activities of nitrogenase, nitrate reductase, glutamine synthetase, glutamate synthase, and glutamate dehydrogenase were investigated. SA exposure increased the number of nodules, fresh and dry nodule masses, leghemoglobin content, and activity of the nitrogen-fixing enzyme nitrogenase compared with the control conditions. Furthermore, SA application enhanced the activities of the enzymes involved in nitrogen assimilation, in both the control and cadmium-stressed plants. The overall results indicate that SA increases the fixation and assimilation of nitrogen regardless of whether the plants are grown in the presence or absence of cadmium.

Sugars are the most important regulators that facilitate many physiological processes, such as photosynthesis, seed germination, flowering, senescence, and many more under various abiotic stresses. Exogenous application of sugars in low concentration promote seed germination, up regulates photosynthesis, promotes flowering, delayed senescence under various unfavorable environmental conditions. However, high concentration of sugars reverses all these physiological process in a concentration dependent manner. Thus, this review focuses the correlation between sugars and their protective functions in several physiological processes against various abiotic stresses. Keeping in mind the multifaceted role of sugars, an attempt has been made to cover the role of sugar-regulated genes associated with photosynthesis, seed germination and senescence. The concentration of sugars determines the expression of these sugar-regulated genes. This review also enlightens the interaction of sugars with several phytohormones, such as abscisic acid, ethylene, cytokinins and gibberellins and its effect on their biosynthesis under abiotic stress conditions.

Cowpea (Vigna unguiculata L.) is an important legume well grown in semiarid and arid environment. Hydrogen peroxide solutions (0.1, 0.5, 1.0, and 1.5 mM) have been used to optimize growth and photosynthetic performance of cowpea plant at two growth stages [30 and 45 DAS (days of sowing)]. Foliar application of H2O2 at 0.5 > 1.0 mM solution at 29 DAS optimally promoted the photosynthetic attributes [leaf chlorophyll content, net photosynthetic rate (PN), water use efficiency, and maximum quantum yield of PSII (Fv/Fm)] and growth performance [root and shoot length; fresh and dry weight] of plants where the responses were more significant at the later growth stage. It was favored by activity of enzymes as carbonic anhydrase [CA; E.C. 4.2.1.1] and nitrate reductase [NR, E.C. 1.6.6.1] and those of antioxidant enzymes viz. peroxidase [POX; EC 1.11.1.7], catalase [CAT; EC 1.11.1.6], and superoxide dismutase [SOD; EC 1.15.1.1] and leaf proline content. Strengthened root system and antioxidant activity, particularly leaf proline level appeared to be the key factor for efficient photosynthesis and growth responses.

Seeds of chickpea were sown in the pots supplemented with 0, 25, 50 or 100 mg of cadmium per kg of soil. At the stage of 30 days after sowing (DAS), the raised plants were sprayed with 20 mM proline except for the control plants which received double distilled water (DDW). The increasing degree of damage caused by the increasing concentration of Cd in soil was partially overcome by proline application. The treatment of 25 mg Cd fed plants with 20 mM proline increased significantly the nodulation parameters, leghemoglobin and carbohydrate content, leaf nitrogen and root nitrate content, activity of enzymes nitrogenase (E.C 1.18.6.1), nitrate reductase (E.C. 1.6.6.1), glutamine synthetase (GS) (E.C 6.3.1.2), glutamate synthase (GOGAT) (E.C 1.4.7.1) and glutamate dehydrogenase (GDH) (E.C 1.4.1.3) over that of the control. The value of these parameters was found to be at par with that of the control in the plants exposed to 50 mg Cd per kg of soil and also treated with 20 mM proline. However, the treatment was not found to be effective in alleviating the adverse effects of 100 mg Cd per kg of soil.

The present study was carried out to elucidate the protective role of sodium nitroprusside (SNP) against salt (NaCl) stress given as seed soaking in tomato (Solanum lycopersicum Mill. cv. K-21). For this experiment prior to sowing, the surface sterilized tomato seeds were soaked in different concentrations of NaCl solution (50, 100, and 150 mM) for 8 hours. Some NaCl soaked seeds were then transferred to the 10−5 M of SNP solution for 8 hours. The plants were sampled at 60 DAS to assess the nitrate reductase activity, proline content and the activities of antioxidant enzymes. The antioxidant enzyme activity and proline content increased in the plants where SNP was applied as a follow up treatment of the NaCl as seed soaking over the control plants thereby providing stress tolerance to the plants. In case of the nitrate reductase activity the toxic effects generated by the lowest concentration of NaCl (50 mM) was completely neutralized by SNP and partly at higher concentrations (100/150 mM). These results suggest that nitric oxide can be used as a stress alleviator in plants which are grown in the soil contaminated with salinity stress.

Brassinosteroids (BRs) are a class of polyhydroxysteroid plant hormones. The sensitivity of a crop to abiotic/biotic stress is a functional aspect of its response as regulated by the efficient internal buildup of hormones like BRs. A better understanding of how the brassinosteroid isomers differentially affect plant responses in tomato (Solanum lycopersicum L.) is necessary to improve production. Plants of cv. K-21 were grown in a net house and foliage was treated with brassinosteroid isomers 28-homobrassinolide (HBL) and 24-epibrassinolide (EBL) at concentrations of 10−6, 10−8, or 10−10 M. Plants responded more to EBL than to HBL. All treatments increased nitrate reductase activity and the antioxidant system with respect to the control. However, the 10−8 M concentration of EBL produced higher nitrate reductase activity and better stimulated the antioxidant system in tomato. In physiological experiments, different concentrations/modes of stress/hormone(s) were tested and justified in biosynthetic or signa...

Excess cadmium accumulation in shoot decreases the photosynthetic attributes and the activity of carbonic anhydrase (CA; E.C. 4.2.1.1) thereby retarding plant growth metabolism, in a cultivar dependent manner. Two mustard (Brassica juncea) varieties were treated with increasing cadmium doses (0, 25, 50 or 100 mg CdCl2 kg−1 of soil) in the soil in a net house. The photosynthetic features, activity of CA, and the yield attributes were recorded in association with morphological characters. A clear-cut difference in these features was noted among the varieties, where Varuna excelled in its resistance to the cadmium toxicity with better growth and yield, at harvest.