不同浓度N营养条件对水稻生长发育和C、N代谢的影响

Effect of different nitrogen nutrition conditions on the growth and development,and C and N metabolism in rice

为了解不同浓度N营养对水稻生长发育和C、N糖代谢影响效果的特点,采用4种浓度N营养在全生育期内处理水稻,分析其农艺性状、可溶性糖和游离氨基酸含量、色素含量和N转运和代谢关键基因的表达响应。结果表明:水稻叶片内蔗糖含量在正常浓度即0.5和2 mmol·L^(-1) N营养条件下比高浓度即5 mmol·L^(-1)条件下,均高出7倍,茎秆内均高出2倍左右;而在低浓度即0.05 mmol·L^(-1)条件下,叶片和茎秆内蔗糖含量极低。这很可能是由于低N条件导致植株N营养缺乏,光合碳同化作用降低,而高N条件抑制光合作用。同时,水稻各组织中游离氨基酸含量在0.05和0.5 mmol·L^(-1) N条件下很低,2和5 mmol·L^(-1) N条件下含量显著提高,相较前两者,至少升高1倍以上;总体上看,随着外施N浓度增加均显著增加,N营养促进N代谢。有意思的是,叶片中叶绿素含量在0.05到2 mmol·L^(-1) N条件范围内,几乎与水稻组织中游离氨基酸含量的变化趋势一致。在所分析的N转运和代谢的关键基因中,只有在0.05 mmol·L^(-1) N条件下表达显著升高,而大部分基因对施N浓度变化没有明显的表达响应。综上,不同浓度N营养对水稻生长发育和C、N代谢的作用效果具有显著差异。这些结果对深入探究水稻生理代谢分子机制和指导作物施肥实现优质高产提供重要理论基础。

In order to understand the effect of different N nutrition levels on C and N metabolism in rice plant,we treated rice plants with 4 kinds of N nutrition levels during the whole growth period.At the adult growth period,we analyzed the agronomic traits,the content of soluble sugar and free amino acid,pigment content and expression response of some key genes involved in nitrate N transport or N metabolism in the treated rice plant.The result revealed that:the sucrose content in the leaf under 0.5 and 2 mmol·L^(-1) nutrition condition was seven times higher than that under 5 mmol·L^(-1) nutrition condition,and which was about 2 times higher in the stem;meanwhile,sucrose contents in both the leaf and stem were very low under 0.05 mmol·L^(-1) nutrition condition.The result might be due to possibility that the low level of N nutrition application led to N deficiency in rice plant and accordingly lower photosynthesis efficiency,whereas,too high level of N nutrition could inhibit the photosynthesis.In the meantime,amino acid metabolism was obviously enhanced under 2 and 5 mmol·L^(-1) nutrition conditions in rice plant,and it was at least twice as high as that under 0.05 and 0.5 mmol·L^(-1) nutrition conditions,manifesting that N nutrition could promote the N metabolism.Interestingly,under the concentration range from 0.05 and 2 mmol·L^(-1) nutrition,the change trend of pigment content in the leaf was almost consistent with that of amino acid metabolism in rice plant.Among the key genes involved in N transport or N metabolism,only NRT2.1 was significantly increased under 0.05 mmol·L^(-1) nutrition condition,whereas,most of the genes showed no notable expression response to the different N nutrition conditions.Combined the effect of different N nutrition conditions on the growth and development and C,N metabolism in rice plants exhibited notable variance.These results provide an important theoretic basis for further exploring the molecular mechanism on rice physiological metabolism and guidelines for optimal N application to realize high quality and yield of rice.