Studies On Physiological And Biochemical Characteristics Of Peanut Under Aluminum Stress

Peanut cultivars GH21 (Al-resistant) and GH23 (Al sensitive) were selected from 18 cultivars by root elongation experiment, hematoxylin dying and Al content detection of root tip. The changes of physiological and biochemical characteristics of peanut after Al stress were studied with GH21 and GH23 as experimental materials. The results showed that there was less effect of 24 h Al stress on photosynthesis of peanut leaf. Electrolyte leakage of roots under Al stress increased, but that of GH23 was higher than that of GH21. Al increased the contents of superoxide ( · O₂^-), Hydrogen peroxide (H₂O₂ ) and proline of root, but · O₂^- and H₂O₂ increase were higher in GH23 than in GH21, proline increase was higher in GH21 than in GH23. There was not distinct change of MDA content of root from GH21, but it increased significantly in GH23.SOD activity of root from GH21 did not change distinctly after Al stress, but that of GH23 decreased, and the SOD activity was 27.6 % of the control under Al stress at 50μmol·L^-1. POD activity increased, increased proportion of GH21 was higher than that of GH23, it was 32.1% and 28.4% respectivelyunder lOOumol-L'1 Al stress. CAT activity of GH21 increased at Al and decreased at lOOumol-L"1 Al, that of GH23 decreased. Soluble sugar content of GH21 changed little, that of GH23 increased at SOumol-L"1 Al and decreased at 1 OOumol-L"1 Al. Soluble protein content of GH21 decreased, that of GH23 increased at SOumol-L"1 Al and decreased at lOOumol-L"1 Al. Polyphenol oxidase (PPO) activity of GH21 increased at 501-imol-L'1 Al and decreased at lOOumol-L"1 Al, that of GH23 increased.With Al concentration increasing, mitochondrial -02" and MDA contents increased, but it was higher in GH23 than in GH21. After lOOumol-L'1 Al stress, GH21 and GH23 O2" contents increased by 14.5% and 24.9%, MDA contents increased by 39.4% and 51.0%, respectively, compared with the controls. With Al concentration increasing, mitochondrial soluble sugar contents, SOD and POD activities increased, increased quantity of GH21 was higher than that of GH23.Citric acid and succinic acid secretion increased distinctly under Al stress. After Al stress at SOumol-L"1 and lOOumol-L'1, GH21 citric acid secretion increased by 121.8% and 363.6%, GH21 succinic acid secretion increased by 542.3% and 756.7%, Compared with the controls, GH23 citric acid secretion increased by 253.5% and 512.2%, GH23 succinic acid secretion increased by 122.9%and 257.3%, respectively.There is great different Al resistant ability in different peanut cultivars. To keep low membrane lipid peroxidation and increase protective enzyme activity of root tip and mitochondria of root tip of peanut is one of Al resistantmechanisms. There is not positive relationship between organic acid secretion and Al resistance.