水稻氮高效基因型根系分泌物中有机酸和氨基酸的变化特征

采用溶液培养试验，研究水稻氮高效基因型在不同供氮水平下，根系分泌物中有机酸和氨基酸种类及含量的变化情况，并探讨其与氮素利用效率之间的关系。结果表明: 1）水稻氮高效基因型氮积累量随着供氮水平的降低明显下降，而氮素利用效率显著提高; 在供氮水平为20 mg/L时，高效基因型具有较高的氮积累量，且氮素利用效率较低效基因型高42.9%（分蘖期）和21.4%（拔节期）。 2）草酸为高效基因型根系分泌的主要有机酸种类，其分泌量占有机酸总量的80%以上，其次是乙酸和柠檬酸; 有机酸分泌总量和草酸分泌量在分蘖期和拔节期随供氮水平的降低而降低，乙酸和柠檬酸分泌量在拔节期也呈相同趋势; 相同供氮水平下，高效基因型有机酸分泌总量均显著低于低效基因型，且在20 mg/L时差异明显。 3）丙氨酸为高效基因型根系分泌的主要氨基酸种类，其分泌量占氨基酸总量的50%以上，其次是丝氨酸、 谷氨酸、 天冬氨酸、 苯丙氨酸、 甘氨酸和苏氨酸，且氨基酸分泌总量和各组分氨基酸分泌量均随供氮水平的降低而降低; 在低氮水平（10 mg/L和20 mg/L）下，高效基因型氨基酸分泌总量均显著低于低效基因型。4）在分蘖期和拔节期，水稻根系分泌有机酸和氨基酸总量与氮素利用效率均呈显著或极显著负相关，有机酸分泌组分中的草酸和氨基酸分泌组分的天冬氨酸分泌量与氮素利用效率也呈显著或极显著负相关。以上结果表明，低氮条件下水稻氮高效基因型氮效率优势明显，高效基因型氮素利用效率高，有利于体内同化物质的合理分配。

Characteristics of organic acid and amino acid in root exudates of rice genotype with high nitrogen efficiency

  Nitrogen plays important roles in promoting plant growth and development. The purpose of this study was to investigate how N nutrient affect the changes in the root exudates under different nitrogen levels and their relations with nitrogen utilization efficiency of rice nitrogen efficiency genotype. In this research, a hydroponic experiment was carried out in a net room on the farm of Sichuan Agricultural University, Sichuan province, China in 2009, with four nitrogen fertilizer applications, 10 mg/L, 20 mg/L, 40 mg/L and 60 mg/L. The results show that the nitrogen accumulations of the rice nitrogen efficiency genotype significantly are decreased with the nitrogen level decrease at the tillering stage and jointing stage, while the nitrogen utilization efficiencies are significantly increased. The nitrogen accumulations of the nitrogen efficiency genotype are 42.9% at the tillering stage and 21.4% at the jointing stage, which are higher than those of the inefficiency genotype under the nitrogen level of 20 mg/L. As the main kind of organic acids of the nitrogen efficiency genotype, the secretion volume of oxalate acid accounts for more than 80% of the total organic acid, and those of acetic acid and citric acid are followed. The secretion amounts of organic acid and oxalate acid are significantly decreased with the nitrogen level decrease at the tillering and jointing stages, and the amounts of acetic acide and citric acid show the same trend at the jointing stage. Under the same nitrogen level, the total organic acid secretion of the nitrogen efficiency genotype is significantly lower than that of the inefficiency genotype. As the main kinds of amino acid of the nitrogen efficiency genotype, the secretion volume of alanine accounts for more than 50% of the total amino acid, and is followed by serine, glutamic, aspartic, phenylalanine, glycine and threonine acids. Total amino acids’ secretion and all components of amino acid secretion are decreased with the nitrogen level decrease. Under the low nitrogen levels of 10 mg/ L and 20 mg/ L, the total amino acids secretion of the nitrogen efficiency genotype is significantly lower than that of the inefficiency genotype. At the tillering and jointing stages, the total organic acid and oxalate acid are significant or very significant negative correlated with the nitrogen utilization efficiency, and amino acid secretion and aspartic acid as the same. It could be concluded that rice nitrogen efficiency genotype has certain regulation mechanism, which can reasonable allocation in vivo assimilation substance, promote the efficient uptake and utilization of nitrogen in low nitrogen condition.