Abstract
Calcium (Ca) plays important role in plant development and response to various environmental stresses. However, its involvement in mitigation of heavy metal stress in plants remains elusive. In this study, we examined the effect of Ca (50 mM) in controlling cadmium (Cd) uptake in mustard (Brassica juncea L.) plants exposed to toxic levels of Cd (200 mg L−1 and 300 mg L−1). The Cd treatment showed substantial decrease in plant height, root length, dry weight, pigments and protein content. Application of Ca improved the growth and biomass yield of the Cd-stressed mustard seedlings. More importantly, the oil content of mustard seeds of Cd-stressed plants was also enhanced with Ca treatment. Proline was significantly increased in mustard plants under Cd stress, and exogenously sprayed Ca was found to have a positive impact on proline content in Cd-stressed plants. Different concentrations of Cd increased lipid peroxidation but the application of Ca minimized it to appreciable level in Cd-treated plants. Excessive Cd treatment enhanced the activities of antioxidant enzymes superoxide dismutase, ascorbate peroxidase and glutathione reductase, which were further enhanced by the addition of Ca. Additionally, Cd stress caused reduced uptake of essential elements and increased Cd accumulation in roots and shoots. However, application of Ca enhanced the concentration of essential elements and decreased Cd accumulation in Cd-stressed plants. Our results indicated that application of Ca enables mustard plant to withstand the deleterious effect of Cd, resulting in improved growth and seed quality of mustard plants.
Highlights
Heavy metal stress has been increasing at an alarming rate and has become a global issue in the contemporary era
Changing their conformation in response to Ca-binding, calmodulin proteins regulate a variety of mechanisms, including ion transport, gene regulation, cell motility, growth, proliferation, apoptosis and stress tolerance [39,40,41]
We found that Ca application mitigated the negative effect of Cd stress on mustard plants, including their growth and oil content
Summary
Heavy metal stress has been increasing at an alarming rate and has become a global issue in the contemporary era. Heavy metal pollution in soil arises as a result of various anthropogenic activities, such as continuous use of sewage water, sewage sludge and fertilizers [1,2]. Heavy metals have been reported to inhibit the growth and productivity of crops [6,7]. Cadmium (Cd) is well known noxious environmental element due to its great toxicity and high mobility from soil to plants [8]. Being a highly toxic metal pollutant of soil, Cd inhibits root and shoot growth, compresses yield production and is frequently accumulated by agriculturally important crops, entering the food chain with a significant potential to impair human and animal health [11]. Disturbance in the plant water relations is widely known as one of the first harmful effects of Cd toxicity [14], which leads to osmotic stress in plants
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