| Nitric oxide(NO)is an important signaling molecule in vivo, participating in the regulation of plant growth and development and responses of plants to biotic and abiotic environmental stresses. With different varieties of peanut peanut as materials, the experiment studied the mechanism how exogenous NO donor SNP improve and maintain drought resistance, the trend of NO content of leaves produced under drought stress and its relations with with drought resistance and drought-related traits and utilized suitable indicators of NO to identify and evaluate germplasm materials, providing a theoretical basis for peanut varieties breeding and cultivation practices. The main findings were as follows:1 NO content after supplying exogenous NO of NO content of different varietiesUnder normal conditions, NO content of leaflets treated with SNP of four varieties were higher than non-treated leaflets. Because NO treatment might impact adjacent blades indirectly, NO content of adjacent blades also changed. NO treatment decreased NO content of the upper leaves of treated leaves while exogenous NO increased NO content of the lower leaves under normal water-supply condition and PEG stress. Under PEG treatment, although NO treatment increased NO content of the lower leaves, the difference did not achieve significance. The results showed exogenous NO could induce changes of endogenous NO content in other parts or transform in plants.2 The adjustment of exogenous NO on growth and antioxidant capacity of peanuts under PEG stressUnder normal water-supply, exogenous NO increased POD activity and soluble protein content of four different varieties with different degrees. Under PEG stress, exogenous NO increased POD activity, CAT activity and decreased O2- production rate, thus relievingoxidative damage caused by the stress. Correlation analysis showed that the correlation efficient of soluble protein content, O2-production rate, MDA content, CAT activity and endogenous NO content correlation were significant or highly significant, indicating that exogenous NO might play a role in increasing antioxidant enzyme activity and reducing reactive oxygen species3 The Response of NO content of different varieties to drought stressNongda818, Rugaoxiyangsheng, Shanhua11, ICG6848 and Baisha1016 was treated with different degrees of drought at seedling stage. Based on the plant biomass of drought-resistant peanut varieties, the results of drought resistance coefficient showed that Nongda818 Rugaoxiyangsheng, Shanhua11, ICG6848 and Baisha1016 were drought-resistant, while ICG6848 and Baisha 1016 were drought resistant. Under normal water-supply condition,there existed a different of NO content of different varieties. NO content of different drought treatment of Nongda818, Rugaoxiyangsheng and Shanhua11 significantly increased with a different rate. NO content of mild drought treatment of Nongda818 was the highest, with an increase of 153.3%, while Rugaoxiyangsheng and Shanhua11 was the highest under moderate drought, with and increase of 108.7% and 86.8%. However, NO content of ICG6848 and Baisha1016 did not increase until the drought degree increased to severe drought..4 The relationship of NO and drought resistanceThe correlation efficient of NO content and plant biomass, NO content and drought resistance coefficient under different drought degrees were not significant(P>0.05). Among three drought treatment, the correlation coefficient was the biggest under moderate drought.The results of clustering analysis of NO content and its relative value under drought stress and the results of clustering analysis of drought resistance coefficient under different treatments were found similar. Nongda818, Rugaoxiyangsheng and Shanhua11 were clasified as a class,suggesting that drought resistant varieties might have lower NO content and higher NO ratio..Under drought stress, photosynthetic rate(Pn), transpiration rate(Tr), intercellular CO2concentration(Ci), maximum photochemical efficiency(Fv/Fm), actual photochemical efficiency(ΦPSII)decreased with the degrees of drought. And the increase degrees of SOD,POD, CAT activity varied with different drought treatment while MDA content and O2-production rate was increasing under drought stress. Correlation analysis showed that there was a big correlation efficient between Pn, NPQ(non-photochemical quenching),q P(photochemical quenching), Φ PSII, SOD activity and soluble protein content and NO content, suggesting that NO could affect the outcome of the response of ecophysiologicalmechanisms to drought through photosynthesis and fluorescence parameters and other physiological and biochemical characteristics.5 Identification and evaluation of NO of germplasmNO content under normal water-supply conditions and the variation width of NO content under drought stress could be an indicator to identify and evaluate NO of varieties. Based on that NO content under normal water-supply condition less than 3.077ng?g-1 was considered to be low, and the ratio less than 1.596 was low induced., the identification results of all germplasm materials showed 86 materias belonged to low content and low induction, 56 belonged to low content and high induction, 71 were high content and low induction, and the others belonged to high content and high induction, which the number of varieties of high content and high induction was the least. The result could provide a basis evident for understanding NO production ability of different varieties in germplasm and seeking varieties with advantages of different drought resistance mechanism from large quantity of varieties. |
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