Effects of 28-homobrassinolide on Seedling Growth, Lipid Peroxidation and Antioxidative Enzyme Activities under Nickel Stress in Seedlings of Zea mays L

The Exogenous Application of 24-Epibrassinolide (24-EBL) Increases the Cd and Pb Resilience in Zea mays (L.) by Regulating the Growth and Physiological Mechanism

Heavy metals (HMs) at a concentration above the threshold level act as environmental pollutants and very often threaten the agricultural productivity globally. Finding affordable and environmentally sustainable deliverables to address this issue is therefore a top focus. Phytohormones alleviate the HMs-induced toxicity and positively influence the plant growth. Considering the importance of phytohormones, the present study aimed to assess the effect of 24-epibrassinolide (24-EBL; 10 µM) as seed soaking treatment on growth performance of Zea mays (L.) contaminated separately with increasing concentrations (50-400 mg.kg-1) of lead (Pb) and cadmium (Cd). With increasing metal concentrations, growth and plant biometric criteria were reduced. For instance, Cd at 400 mg.kg-1 soil reduced the germination efficiency (56%), root (77%) and shoot (69%) dry weight, total chlorophyll (64%), and carotenoid content (45%). Contrarily, both HMs caused increase in stress biomarkers and antioxidant enzymes in seedling. However, exogenous administration of 24-EBL significantly enhanced the growth attributes, photosynthetic pigments, proline, MDA, and antioxidant enzyme activity while reducing the harmful effects of HMs stress on Z. mays. For instance, 24-EBL (10 µM) improved the germination percentage, root biomass, chl a, chl b, total chlorophyll, and carotenoid content by 16, 21, 17, 34, 18, and 15%, respectively, in 50 mg.Pb.kg-1 soil-treated Z. mays plants. Furthermore, the amounts of proline, MDA, and antioxidant enzymes in foliage of Z. mays were interestingly and dramatically lowered by 24-EBL application. Uptake of metals in plant organs was significantly reduced when 24-EBL was applied to Pb- and Cd-treated Z. mays. The recent findings help us better understand how 24-EBL regulates growth and development of Z. mays as well as how it boosts HMs' resilience, which could increase the possibility of employing 24-EBL to increase Z. mays productivity. Thus, the present findings confirmed the potentiality of pre-soaking the seed in 24-EBL solution that neutralizes the toxic effects of heavy metals in Z. mays plants. Therefore, it is suggested that applying phytohormones including 24-EBL in removal of heavy metal stress in plants is the best possible solution in sustainable agriculture.

A review on adsorptive separation of toxic metals from aquatic system using biochar produced from agro-waste

Water is a basic and significant asset for living beings. Water assets are progressively diminishing due to huge populace development, industrial activities, urbanization and rural exercises. Few heavy metals include zinc, copper, lead, nickel, cadmium and so forth can easily transfer into the water system either direct or indirect activities of electroplating, mining, tannery, painting, fertilizer industries and so forth. The different treatment techniques have been utilized to eliminate the heavy metals from aquatic system, which includes coagulation/flocculation, precipitation, membrane filtration, oxidation, flotation, ion exchange, photo catalysis and adsorption. The adsorption technique is a better option than other techniques because it can eliminate heavy metals even at lower metal ions concentration, simplicity and better regeneration behavior. Agricultural wastes are low-cost biosorbent and typically containing cellulose have the ability to absorb a variety of contaminants. It is important to note that almost all agro wastes are no longer used in their original form but are instead processed in a variety of techniques to improve the adsorption capacity of the substance. The wide range of adsorption capacities for agro waste materials were observed and almost more than 99% removal of toxic pollutants from aquatic systems were achieved using modified agro-waste materials. The present review aims at the water pollution due to heavy metals, as well as various heavy metal removal treatment procedures. The primary objectives of this research is to include an overview of adsorption and various agriculture based adsorbents and its comparison in heavy metal removal.

Foliar Application of 24-Epibrassinolide Improves Growth, Ascorbate-Glutathione Cycle, and Glyoxalase System in Brown Mustard (Brassica juncea (L.) Czern.) under Cadmium Toxicity

Cadmium (Cd) metal toxicity is a crucial ecological matter that requires immediate efforts to mitigate it. Brassica juncea plants were exposed to Cd (0 and 200 µM as CdSO₄) and foliar application of 24-Epibrassinolide (EBR) (0, 10⁻⁷ and 10⁻⁵ M). The toxic effect of Cd was evident in terms of declined growth and biomass yield, lowered levels of pigment content and chlorophyll fluorescence, and reduction in gas exchange attributes. The levels of proline and glycinebetaine increased in response to Cd treatment. There was an imperative rise in the contents of H₂O₂ and malondialdehyde as well as electrolyte leakage in the Cd-stressed plants. With the application of EBR, there was a significant replenishment in growth attributes and photosynthetic efficacy. The contents of ROS (reactive oxygen species) and malondialdehyde as well as electrolyte leakage were reduced by the hormone supplementation. Enhancement in the contents of glutathione and ascorbic acid, and the activities of enzymes of the antioxidative defense system and glyoxalase system was recorded in response to Cd as well as hormone treatment. The in situ levels of Cd in roots and shoot were augmented in response to Cd treatment, but were found to be lowered by the EBR application.

Study the effect of 24-epibrassinolide application on the Cu/Zn-SOD expression and tolerance to drought stress in common bean

To study the possibility of increasing the drought tolerance of common bean with the exogenous application of 24-epibrassinolide (EBL), an experiment was conducted in 2016 and 2017. In this experiment, two irrigation levels (optimal irrigation and drought stress) were applied to the main plots and two common bean genotypes (Kusha cultivar and COS16 genotype) and four EBL concentrations (0, 2, 4, and 6 μM) were allocated to sub-plots as factorial. In the flowering stage, drought stress was applied and plants were sprayed with EBL. The results showed that drought stress reduced relative water content (RWC) and increased proline content, malondialdehyde (MDA) content, and antioxidant enzymes activity. However, exogenous application of EBL reduced the seed yield loss and increased the drought stress tolerance in both common bean genotypes by decreasing the MDA content and increasing the RWC, proline content, antioxidant enzymes activity, and nitrate reductase activity. It can be concluded that foliar spray of 4 µM EBL as the best concentration may increase the seed yield and enhance the drought stress tolerance of common bean. Also, Cu/Zn-SOD was up-regulated in response to the drought stress and exogenous EBL. The COS16 genotype showed better response to the drought stress and exogenous EBL than the Kusha cultivar, because of the higher up-regulation of Cu/Zn-SOD in this genotype compared to the Kusha cultivar. Therefore, EBL can be used as a plant growth regulator to enhance drought stress tolerance and minimize the seed yield loss of common bean caused by water deficit.

Nickel toxicity in plants: reasons, toxic effects, tolerance mechanisms, and remediation possibilities-a review

Nickel (Ni) is a naturally occurring metal, but anthropogenic activities such as industrialization, use of fertilizers, chemicals, and sewage sludge have increased its concentration in the environment up to undesirable levels. Ni is considered to be essential for plant growth at low concentration; however, Ni pollution is increasing in the environment, and therefore, it is important to understand its functional roles and toxic effects on plants. This review emphasizes the environmental sources of Ni, its essentiality, effects, tolerance mechanisms, possible remediation approaches, and research direction that may help in interdisciplinary studies to assess the significance of Ni toxicity. Briefly, Ni affects plant growth both positively and negatively, depending on the concentration present in the growth medium. On the positive side, Ni is essential for normal growth, enzymatic activities (e.g., urease), nitrogen metabolism, iron uptake, and specific metabolic reactions. On the negative side, Ni reduces seed germination, root and shoot growth, biomass accumulation, and final production. Moreover, Ni toxicity also causes chlorosis and necrosis and inhibits various physiological processes (photosynthesis, transpiration) and cause oxidative damage in plants. The threat associated with Ni is increased as Ni concentration increases day by day in the environment, particularly in soils; therefore, it would be hazardous for crop production in the near future. Additionally, the lack of information regarding the mechanisms of Ni tolerance in plants further intensifies this situation. Therefore, future research should be focused on approachable and prominent solutions in order to minimize the entry of Ni into our ecosystems.

Biogeochemical behavior of nickel under different abiotic stresses: toxicity and detoxification mechanisms in plants

Nickel (Ni) is a ubiquitous and highly important heavy metal. At low levels, Ni plays an essential role in plants such as its role in urease, superoxide dismutase, methyl-coenzyme M reductase, hydrogenase, acetyl-coenzyme A synthase, and carbon monoxide dehydrogenase enzyme. Although its deficiency in crops is very uncommon, but in the past few years, many studies have demonstrated Ni deficiency symptoms in plants. On the other hand, high levels of applied Ni can provoke numerous toxic effects (such as biochemical, physiological, and morphological) in plant tissues. Most importantly, from an ecological and risk assessment point of view, this metal has narrow ranges of its essential, beneficial, and toxic concentrations to plants, which significantly vary with plant species. This implies that it is of great importance to monitor the levels of Ni in different environmental compartments from which it can enter plants. Additionally, several abiotic stresses (such as salinity and drought) have been reported to affect the biogeochemical behavior of Ni in the soil-plant system. Thus, it is also important to assess Ni behavior critically under different abiotic stresses, which can greatly affect its role being an essential or toxic element. This review summarizes and critically discusses data about sources, bioavailability, and adsorption/desorption of Ni in soil; its soil-plant transfer and effect on other competing ions; accumulation in different plant tissues; essential and toxic effects inside plants; and tolerance mechanisms adopted by plants under Ni stress.

Modulation of antioxidative defense expression and osmolyte content by co-application of 24-epibrassinolide and salicylic acid in Pb exposed Indian mustard plants

The study focuses on potential of combined pre-soaking treatment of 24-Epibrassinolide (EBL) and Salicylic acid (SA) in alleviating Pb phytotoxicity in Brassica juncea L. plants. The seeds after treatment with combination of both the hormones were sown in mixture of soil, sand and manure (3:1:1) and were exposed to Pb concentrations (0.25mM, 0.50mM and 0.75mM). After 30 days of growth, the plants were harvested and processed, for quantification of various metabolites. It was found that pre-sowing of seeds in combination of EBL and SA, mitigated the adverse effects of metal stress by modulating antioxidative defense response and enhanced osmolyte contents. Dry matter content and heavy metal tolerance index were enhanced in response to co-application of EBL and SA. The levels of superoxide anions, hydrogen peroxide and malondialdehyde were lowered by the combined treatment of hormones. Enhancement in activities of guaiacol peroxidase, catalase, glutathione reductase and glutathione-s-transferase were recorded. Contents of glutathione, tocopherol and ascorbic acid were also enhanced in response to co-application of both hormones. Expression of POD, CAT, GR and GST1 genes were up-regulated whereas SOD gene was observed to be down-regulated. Contents of proline, trehalose and glycine betaine were also reported to be elevated as a result of treatment with EBL+SA. The results suggest that co-application of EBL+SA may play an imperative role in improving the antioxidative defense expression of B. juncea plants to combat the oxidative stress generated by Pb toxicity.

Brassinosteroids and Response of Plants to Heavy Metals Action

Brassinosteroids (BRs) are a widespread group of plant hormones. These phytohormones play a crucial role in the regulation of growth and development of various plant species, and they demonstrate high biological activity. BRs are considered to demonstrate protective activity in the plants exposed to various stresses. Due to rapid industrialization and urbanization, heavy metals have become one of the most important plant stressors. In plants, accumulation of heavy metals beyond the critical levels leads to oxidative stress. However, BRs may inhibit the degradation of lipids, resulted from the overproduction of reactive oxygen species under stress conditions, and increase the activity of antioxidants. They also have the ability to promote phytochelatins synthesis.

Effect of drought stress on superoxide dismutase activity in two species of Haloxylon aphyllum and Haloxylon persicum

Superoxide dismutase activity changes were studied at different periodic tensions using of spectrophotometric measurement of decline in NitroBlue Tetrazolium reduction to Blue Formazan at 560 nm in Haloxylon aphyllum and Haloxylon persicum. The aim of this study was to investigate the changes of superoxide dismutase in applied drought stress in two species of Haloxylon. The results showed that the effect of drought stress on increase in superoxide dismutase activity was significant (p < 0.01) in two haloxylon species. Drought increased enzyme activity at severe tensions. When two haloxylon species were placed under 7 and 14 days no-watering treatments (mild tensions), the enzyme activity was more than its activity in control treatment and less than one in 21 and 28 days no-watering treatments (severe tensions). The enzyme activity in branchlets of Haloxylon aphyllum under 21 and 28 days no-watering treatments was 20.2 and 29.5% more than its activity under control treatment respectively. This activity in Haloxylon persicum was 21.6 and 31.4% more than its activity under control treatment, respectively. With the advent of drought, superoxide dismutase activity increased in two species of haloxylon. The increasing of superoxide dismutase activity in time of dryness advent in Haloxylon aphyllum was more than Haloxylon persicum, which can be raised as an acceptable factor and vindicator in being more resistant of Haloxylon aphyllum to environmental drought.

In Vitro Effects of Brassinosteroids on the Growth and Antioxidant Enzyme Activities in Groundnut

This paper deals with the in vitro effects of brassinosteroids (BRs) on growth in the form of multiple shoots, chlorophyll content, Hill reaction activity (HRA), activities of catalase (CAT), peroxidase (POX), polyphenol oxidase (PPX), and ascorbate peroxidase (APX) in Arachis hypogaea L. genotypes (M-13 and PBS24030). In vitro impact of BR on shoot multiplication potential was found to be the best at 1 mL L−1 with BA (3 mg L−1) in both the cultivars. Flowering was observed in PBS24030 on the medium containing 2.0 mL L−1 BR with 3 mg L−1 BA. Rhizogenesis was noticed in the presence of BR alone. Total chlorophyll content and HRA were highest at 2.0 mL L−1 with BA in M-13 and 1.0 mL L−1 with BA in PBS24030. Antioxidant enzyme activities were increased in the presence of BR whether alone or in combination with BA in both the cultivars. However, progressive decline was observed in case of MDA content. The results obtained in the study clearly indicated not only the in vitro establishment of groundnut cultivars in the presence of BR alone and in combination with BA but also its effect on various growth promotory physiological parameters.

Physiological and biochemical effect of 24-epibrassinoslide on cold tolerance in maize seedlings

Germination and early seedling growth are important for establishment of maize because maize is chilling sensitive crop and low temperature during early period of growth can be detrimental to subsequent crop growth and productivity. Therefore, it is important to protect maize seedling from cold stress. A study was conducted on induced cold tolerance by 24-epibrassinoslide (EBR) at the Indian Agricultural Research Institute, New Delhi, India. Maize seedlings were raised in green house condition (25/18 °C day-night temperatures). Ten days old seedlings were treated with EBR (0.0, 0.01, 0.1, 1.0 and 10 μM) and then divided into two sets, one set was kept in greenhouse (25/18 °C day-night temperatures) and another was transferred to net house (cold stress). Data on various morpho-physiological traits was recorded after 7, 14 and 21 days of treatment. Exogenous application of 1.0 μM EBR had significant effect on growth and morpho-physiological traits under both conditions. The maize seedlings treated with EBR were more tolerant to cold stress than the untreated one. Significant increase in plant height, dry matter accumulation, chlorophyll content, total soluble proteins and starch contents was observed under both conditions, however, the results were more pronounced under cold stress. 1.0 μ M concentration being the most effective under both conditions. Maintenance of high tissue water content, reduced membrane injury index, increased total chlorophyll, soluble sugar and protein content were taken as the possible indicators of EBR induced chilling tolerance.

Effect of 28-homobrassinolide on antioxidant defence system in Raphanus sativus L. under chromium toxicity

Heavy metals have emerged as major environmental contaminants due to rapid industrialization and urbanization. The genotoxic, mutagenic and carcinogenic effects of heavy metal like chromium (Cr) on man, animals and plants have been documented. In plants, accumulation of heavy metals beyond critical levels generates oxidative stress. This stress is generally overcome by antioxidant defence system and stress shielding phytohormones. Thus, the present study has been focused to analyze the effect of one of imperative group of plant hormones, i.e., brassinosteroids (BRs) which have been reported for its protective properties for wide array of environmental stresses. Raphanus sativus L. (Pusa Chetaki) seeds pre-treated with different concentrations of 28-homobrassinolide (28-HBL) were raised under various concentrations of Cr(VI). It was observed that 28-HBL treatment considerably reduced the impact of Cr-stress on seedlings which was evinced upon analysis of morphological and biochemical parameters of 7-days old radish seedlings. The toxic effects of Cr in terms of reduced growth, lowered contents of chlorophyll (Chl), protein, proline; increased malondialdehyde (MDA) content and elevated metal uptake were ameliorated by applications of 28-HBL. Also, the activities of all the antioxidant enzymes except guaiacol peroxidase (POD), increased significantly when subjected to Cr stress in combination with 28-HBL. Overall, seed pre-soaking treatment of 28-HBL at 10(-7) M was most effective in ameliorating Cr stress. The present work emphasizes the protective role of 28-HBL on regulation of antioxidant enzymes and its possible link in amelioration of stress in plants.

Nickel: an overview of uptake, essentiality and toxicity in plants

Nickel even though recognized as a trace element, its metabolism is very decisive for certain enzyme activities, maintaining proper cellular redox state and various other biochemical, physiological and growth responses. Study of the aspects related with uptake, transport and distributive localization of Ni is very important in various cellular metabolic processes particularly under increased nitrogen metabolism. This review article, in core, encompasses the dual behavior of Ni in plants emphasizing its systemic partitioning, essentiality and ill effects. However, the core mechanism of molecules involved and the successive physiological conditions required starting from the soil absorption, neutralization and toxicity generated is still elusive, and varies among the plants.

Epibrassinolide induces changes in indole-3-acetic acid, abscisic acid and polyamine concentrations and enhances antioxidant potential of radish seedlings under copper stress

In the present study, the effects of epibrassinolide (EBL) on indole-3-acetic acid (IAA), abscisic acid (ABA) and polyamine (PA) tissue concentrations and antioxidant potential of 7-day-old Raphanus sativus L. cv. 'Pusa chetki' seedlings grown under Cu stress were investigated. EBL treatment alone or in combination with Cu enhanced free and bound IAA titers when compared with the metal alone. Modest increases in free and bound ABA contents were observed for EBL treatment alone. However, the combination of EBL with Cu caused major increases in both forms of ABA, over Cu alone. Among the PAs analyzed, only putrescine and cadaverine concentrations were enhanced by EBL treatment alone. By contrast, a significant decline in putrescine and spermine contents was found in seedlings treated with EBL plus Cu. EBL treatments alone or in combination with Cu enhanced activities of guaiacol peroxidase (EC1.11.1.7), catalase (EC 1.11.1.6), superoxide dismutase (EC 1.15.1.1) and glutathione reductase (EC 1.6.4.2) and protein contents in comparison with metal and control treatments. A major decrease in malondialdehyde content was also recorded for EBL treatments with or without Cu. An increase in phytochelatin content was also observed in seedlings treated with EBL alone or in combination with Cu. Major improvement in radical scavenging activities, as attested by the antioxidant activity assay using DPPH (1,1-diphenylpicrylhydrazyl), and elevated deoxyribose and reducing powers, along with increased contents of ascorbic acid, total phenols and proline, also suggest a major influence of EBL application in mitigating copper-induced oxidative stress in radish seedlings.