Relationship between activities of nitrogen assimilation enzymes and leaf color of rice

Chinese. 【目的】明确水稻叶色变化的内在生理机制。【方法】采用无氮肥和常规氮肥两个处理的水培试验,测定水稻地上部不同叶位叶片叶色值、叶绿素含量及氮素同化关键酶活性的变化。【结果】在氮饥饿和常规施肥条件下,水稻地上部不同叶位的叶色具有明显的黑黄变化规律。氮饥饿处理剑叶抽出前不同叶位叶片叶色值基本上表现为顶二叶〉顶一叶〉顶三叶,剑叶抽出后表现为顶一叶〉顶二叶〉顶三叶。不同叶位叶片GS、GOGAT活性分别在拔节期、剑叶抽出期出现两次高峰,各叶位的叶片GS、GOGAT活性基本表现为顶二叶〉顶一叶〉顶三叶。不同叶位叶片的GOGAT活性与当周叶片的SPAD值、叶绿素a、叶绿素b及叶绿素（a＋b）含量均呈显著或极显著相关。常规施肥处理条件下水稻叶色及酶活性在整个生育期变化趋势与氮饥饿处理相似,GS酶活性与酶活性测定一周后的叶色关系非常密切,GOGAT活性与顶三、四叶叶色呈显著负相关,与酶活性测定1周后顶二、顶三叶的叶绿素a含量、2周后顶二、顶三叶的叶绿素（a＋b）含量及2周后顶二叶的叶绿素b含量也呈显著正相关。【结论】水稻叶色变化是一个复杂的生理生化代谢过程,水稻不同叶位叶片叶色及氮素同化关键酶GS、GOGAT酶活性均具有明显的高低变化，氮素同化关键酶活性高低与叶绿素的合成及叶色变化具有密切的因果关系，在叶绿素的合成和叶色形成过程中具有一定作用。水稻叶色黑黄变化是一个受内生节奏制约的生物学过程，氮素水平对叶色深浅具有一定的调节作用，但不能改变内生黑黄变化节奏。

English. [Objective] To reveal the physiological mechanism of changes of rice leaf color. [Method] The dynamic change of upper-most three leaves color and activities of nitrogen assimilation enzymes of rice was studied in solution experiment with nitrogen stress and normal nitrogen concentration. [Result] The results showed that there were significant changes of leaf color during growing stage even with nitrogen stress. The value of SPAD at different leaf positions were 2nd leaf〉 1st leaf〉3rd leaf from top and 1st leaf〉2nd leaf〉3rd leaf before and after flag leaf extracting, respectively. There were two peak values of activity of GS and GOGAT during jointing stage and flag leaf extracting stage, the activities of GS and GOGAT were 1st leaf〉2nd leaf〉3rd leaf. The activities of GOGAT correlated closely with SPAD values, chlorophyll a,b and a＋b content. The dynamic change of the enzymes activities and leaf color of the normal nitrogen treatment during the whole growing period was similar to the nitrogen stress treatment, the activity of GS had close relationship with the leaf color after one week, the activity of GOGAT had significant negative correlation with the leaf color of 3rd and 4th leaf, and had significant corralation with the chlorophyll a content of 2nd leaf, and the chlorophyll （a＋b） content of 2nd and 3rd leaf and the chlorophyll b content of 2nd leaf after two weeks. [Conclusion] The dynamic change of leaf color of rice is a complicated physiological and biochemical metabolism process, the color of leaf at diferent positions and the activities of key enzymes of nitrogen metabolism GS and GOGAT had obvious changes respectively. The activity of nitrogen metabolism enzymes had significant relations with synthesis of chlorophyll and the change of leaf color, and also had effects on its synthesis. The change of leaf color is a biological process which was restrained by inherent rhythm. To some extent, nitrogen content had regulative effecct on the depth of leaf color, but could not change the inherent rhythm.