Alleviation of cadmium toxicity by silicon is related to elevated photosynthesis, antioxidant enzymes; suppressed cadmium uptake and oxidative stress in cotton

Abstract

Biotic systems face immense environmental hazards such as accumulation of heavy metals, particularly in agricultural ecosystems that might cause deterioration of yield and quality of crops. In this study, we evaluated the role of silicon (Si) in alleviating the heavy metal (Cd) stress tolerance in cotton by analyzing the induced Physio-chemical changes. Cotton plants were grown in hydroponic culture with three different Cd levels (0, 1 and 5μM) along with two Si treatment levels (0 and 1mM). The data showed that Cd alone reduced the plant growth as well as the efficiency of antioxidant activity as compared to control plants. Plant growth, gas exchange characteristics (net photosynthetic rate, stomatal conductance, transpiration rate, water use efficiency) chlorophyll contents, and carotenoids as well as the performance of antioxidant enzymes were improved by the exogenous application of Si. The adverse effects of Cd on plant growth were alleviated by the exogenous application of Si. It was observed that Si effectively mitigated the adverse effects of Cd on cotton plants and markedly enhanced the growth, biomass and photosynthetic parameters while decreased the contents of malondialdehyde (MDA), hydrogen peroxide (H2O2) and electrolytic leakage (EL). The antioxidant enzyme activities in cotton leaves and roots increased significantly, when Si was added to control as well as Cd stressed plants. In conclusion, Si improved the growth and photosynthesis attributes of cotton plants by mitigating the adverse effects of Cd stress through reduced EL, MDA and H2O2 contents and improved activities of antioxidant enzymes.

Keywords: Antioxidant enzymes; Cadmium; Cotton; Growth; Oxidative stress; Silicon.