Silicon effects on antioxidative enzymes and lipid peroxidation in leaves and roots of peanut under aluminum stress

Silicon (Si) can enhance plant defense against biotic and abiotic stresses, but little is known of its possible alleviation of aluminum (Al) stress. In this study, we find out how Si may mediate Al stress based on changes in root morphological parameters, biomass, physiological attributes and concentrations of Al and Si in peanut (Arachis hypogaea L., cv. Zhongkaihua 99). The peanut was raised with (80 mg L-1) or without Si in the growth chamber under 0 and toxic Al (160 mg L-1) levels. Aluminum stress reduced the root dry weight by 52.4 %, shoot dry weight by 33.9 % and root-to-shoot ratio (R/S) by 28.8 %. However, it increased the activities of catalase in leaves and roots by as much as 161.6 and 149.0 %, superoxide dismutase by 141.7 and 147.0 %, and peroxidases by 62.0 and 64.1 %. The Si-treated peanut suffered less from Al stress through improvements in photosynthesis, biomass and R/S. The malondialdehyde, an index of membrane damage decreased significantly by 26.0 and 28.2 % in peanut leaf and root with silicon application under Al toxicity. For the peanut treated with Al, tissue concentration of Al increased by 371.5 % in the root, 20.9 % in the stem and 37.8 % in the leaf, much of the uptake was partitioned to the root. These concentrations decreased by 40.7, 5.3 and 25.6 %, respectively, following Si application.