Effects of lanthanum on the antioxidant capacity of chloroplasts and chlorophyll fluorescence parameters of maize seedlings under chromium stress

Effects of lanthanum chloride (LaCl3) on chromium tolerance of maize were investigated at chloroplast level. The results showed that Cr stress significantly increased activities of ascorbate peroxidase, glutathione reductase, monodehydroascorbate reductase, dehydroascorbate reductase, superoxide dismutase, and glutathione peroxidase, nonphotochemical quenching, malondialdehyde (MDA) and hydrogen peroxide contents, but significantly reduced the ratios of reduced ascorbate to dehydroascorbate and reduced glutathione to oxidized glutathione, the contents of chlorophyll and carotenoids, maximum photochemical efficiency of PSII, photochemical quenching, quantum efficiency of PSII photochemistry, net photosynthetic rate, plant height and biomass, compared with control. Compared to Cr stress alone, LaCl3 significantly reduced MDA and H2O2 contents and increased other indicators under Cr stress. LaCl3 alone also enhanced above indicators except MDA and H2O2, compared with control. Our results suggested that LaCl3 improved the Cr tolerance of maize crops by upregulating the antioxidant capacity and the function of chloroplasts.