ABSTRACT
Brassinosteroids have been extensively used to overcome various abiotic stresses. But its role in combined stress of salt and excess copper remains unexplored. Seeds of two cultivars (Rocket and Jumbo) of Cucumis sativus were grown in sand amended with copper (100 mg kg(-1)), and developed seedlings were exposed to salt stress in the form of NaCl (150 mM) at the 30-day stage of growth for 3 days. These seedlings were subsequently sprayed with 0 or 0.01 µM of 24-epibrassinolide (EBL) at the 35-day stage. The plants exposed to NaCl and Cu in combination exhibited a significant decline in fresh and dry mass of plant, chlorophyll content, activities of carbonic anhydrase, net photosynthetic rate and maximum quantum yield of the PSII primary photochemistry followed by NaCl and Cu stress alone, more severely in Jumbo than in Rocket. However, the follow-up treatment with EBL to the stressed and nonstressed plant improved growth, chlorophyll content, carbonic anhydrase activity and photosynthetic efficiency, and further enhanced the activity of various antioxidant enzymes viz. catalase, peroxidase and superoxide dismutase and content of proline at the 40-day stage of growth, and the response of the hormone was more effective in Rocket than in Jumbo. The elevated level of antioxidant enzymes as well as proline could have conferred tolerance to the NaCl- and/or Cu-stressed plants resulting in improved growth, water relations and photosynthetic attributes. Furthermore, antioxidant enzyme activity and proline content were more enhanced in Rocket than in Jumbo cultivar.
Subject(s)
Brassinosteroids/pharmacology , Copper/toxicity , Cucumis sativus/physiology , Photosynthesis/drug effects , Proline/metabolism , Protective Agents/pharmacology , Soil Pollutants/toxicity , Steroids, Heterocyclic/pharmacology , Cucumis sativus/drug effects , Peroxidase/metabolism , Peroxidases/metabolism , Salt Tolerance/drug effects , Sodium Chloride/toxicity , Superoxide Dismutase/metabolismABSTRACT
The objective of this study was to explore the response of 24-epibrassinolide to improve the biological yield of Ni-tolerant and Ni-sensitive varieties of Vigna radiata and also to test the propositions that 24-epibrassinolide induced up-regulation of antioxidant system protects the efficiency of V. radiata, grown under Ni-stress. Surface sterilized seeds of var. T-44 (Ni-tolerant) and PDM-139 (Ni-sensitive) were soaked in DDW (control), 10(-10), 10(-8), or 10(-6) M of 24-epibrassinolide for 8 h (shotgun approach). These treated seeds were then inoculated with specific Rhizobium grown in sandy loam soil supplemented with different levels of Ni 0, 50, 100, or 150 mg Ni kg(-1) of soil and were allowed to grow for 45-days. At this stage of growth, plants were sampled to assess the various growths and nodule related traits as well as selected biochemical characteristics. The remaining plants were allowed to grow to maturity to study the yield characteristics. The results indicated that plant-fresh and dry mass, number of nodules, their fresh and dry mass, leghemoglobin content, nitrogen and carbohydrate content in the nodules, leaf chlorophyll content, activities of nitrate reductase and carbonic anhydrase decreased proportionately with the increasing concentrations of soil nickel. However, the application of 24-epibrassinolide as shotgun approach (pre-sowing seed soaking) to the nickel-stressed or non-stressed plants improved growth, nodulation and enhanced the activity of various antioxidant enzymes (viz. catalase, peroxidase and superoxide dismutase) and also the content of proline. The up-regulation of antioxidant enzymes as well as proline (osmolyte) triggered by 24-epibrassinolide could have conferred tolerance to the Ni-stressed plants resulting in improved growth, nodulation and yield attributes.
Subject(s)
Antioxidants/metabolism , Brassinosteroids/pharmacology , Fabaceae/drug effects , Fabaceae/metabolism , Nickel/pharmacology , Plant Root Nodulation/drug effects , Steroids, Heterocyclic/pharmacology , Carbonic Anhydrases/metabolism , Catalase/metabolism , Leghemoglobin/metabolism , Nitrate Reductase/metabolism , Nitrogenase/metabolism , Peroxidase/metabolism , Rhizobium/physiology , Root Nodules, Plant/drug effects , Root Nodules, Plant/metabolism , Superoxide Dismutase/metabolismABSTRACT
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.
Subject(s)
Nickel/metabolism , Plants/metabolism , Trace Elements/metabolism , Biological Transport , Nickel/pharmacology , Nickel/toxicity , Plant Development , Plants/drug effects , Soil/chemistry , Soil Pollutants/metabolism , Soil Pollutants/pharmacology , Soil Pollutants/toxicity , Trace Elements/pharmacology , Trace Elements/toxicityABSTRACT
Of all the non-essential heavy metals, cadmium (Cd) is perhaps the metal which has attracted the most attention in soil science and plant nutrition due to its potential toxicity to humans, and also its relative mobility in the soil-plant system. This review summarizes the toxic symptoms of Cd in plants (i.e. growth retardation, alterations of photosynthesis, stomatal movement, enzymatic activities, water relations, interferences with mineral uptake, protein metabolism, membrane functioning, etc.) but also includes the mechanisms of cadmium uptake, translocation and deposition. Moreover, it also throws light on chelation, including identification of Cd ligands present in cytosol and vascular tissue. Cadmium-induced oxidative stress is also considered as one of the most widely studied topics in this review.
Subject(s)
Adaptation, Physiological/drug effects , Cadmium/toxicity , Environmental Pollutants/toxicity , Plants/drug effects , Carbonic Anhydrases/metabolism , Nitrate Reductase/metabolism , Nitrogen Fixation/drug effects , Photosynthesis/drug effects , Plant Development , Plants/enzymology , Plants/metabolism , Proline/metabolismABSTRACT
The plants of Brassica juncea (L) were grown in the presence of NaCl and/or NiCl2 and were sprayed with 1muM of 24-epibrassinolide (EBL) at 15 days after sowing (DAS) and were sampled at 30 DAS. The plants exposed to NaCl and/or NiCl2 exhibited a significant decline in growth, the level of pigments and photosynthetic parameters. However, the follow up treatment with EBL detoxified the stress generated by NaCl and/or NiCl2 and significantly improved the above parameters. The NaCl and/or NiCl2 increased electrolyte leakage and lipid peroxidation, and decreased the membrane stability index (MSI) and relative water content. However, the EBL treatment in absence of the stress improved the MSI and relative water content but could not influence electrolyte leakage and lipid peroxidation. The antioxidative enzymes and the level of proline exhibited a significant increase in response to EBL as well as to NaCl and/or NiCl2 stress.
