Effects of Perchlorate Stress on Growth and Physiological Characteristics of Rice (Oryza sativa L.) Seedlings

Effects of perchlorate stress on the growth and physiological characteristics of rice (Oryza sativa L.) were studied in controlled water culture experiments. Perchlorate stress resulted in varied patterns of biomass allocation to O. sativa organs (roots, stems, and leaves). When stressed with higher perchlorate concentrations, the proportion of root biomass was higher, stem biomass was invariant, while leaf biomass was lower. Coefficients of variation in biomass of different organs followed the order leaf > stem > root, indicating that leaf growth has a higher sensitivity to perchlorate. Compared to the control, the chlorophyll and protein content of leaves and root vigor were lower, whereas malondialdehyde (MDA) content and catalase (CAT) activity were higher and related to perchlorate concentration and duration of stress. Superoxide dismutase (SOD) activity was initially high and then decreased markedly during the experiment, while peroxidase (POX) activity in perchlorate-treated rice was always higher than the POX activity of the control. POX was the most sensitive antioxidant enzyme to perchlorate stress. Correlation analysis showed a positive correlation between SOD activity and the fresh weight of the whole plant, and negative correlation with MDA content. The results suggest that perchlorate could induce oxidative stress and oxidative damage may be the main cause of physiological damage and growth inhibition in rice plants under perchlorate stress.