Physiological mechanism of alleviating aluminum toxicity in rice seedling root by exogenous organic acids

Hydroponic culture experiment was carried out to investigate the use of exogenous organic acids in aluminum detoxification at the germination stage of four hybrid rice varieties.Root length and fresh weight of root,root leakage of electrolytes were detected and antioxidant enzymes(e.g.POD,CAT and APX) activity levels also analyzed.Results show that 1.5mmol/L aluminum treatment slightly hurts rice seedling root and POD and APX activities increase distinctly,though that of CAT has no significant change.Al stress is differentially alleviated after the addition of three different organic acids.Succinic acid shows the most obvious Al stress alleviation. Citric acid,malic acid and the mixture of citric acid and succinic acid have specific effects of variety.At the same time,POD and APX activities exhibit a downward trend while that of CAT changes relatively little after addition of exogenous organic acids, suggesting that metabolic homeostasis of reactive oxygen species (ROS) is disrupted by Al stress. The activity level of antioxidant enzymes in mitochondria is then regulated by exogenous organic acids which causes detoxification of aluminum toxicity during rice germination.