Effects Of Low-light On The Accumulation Of Amino Acids And Related Enzyme Activities At Rice Grain-filling Stage

The japonica rice variety Koshihikari and indica rice variety IR72were selected as the experiment materials, and the shading of49%and74%were used to study on the effects of low-light on the content of glutamic family amino acids, aspartate family amino acids and alanine family amino acids and their metabolic enzyme activity during rice grain filling, while the natural light was used as the control check. The results indicated that:1. The GLU content in grains changed as a diauxie curve during rice grain filling. The low-light increased the GLU content in grains and delayed the first peak of which in Koshihikari, without any change of which in IR72. There was no significant difference of GLU content in grains between49%-shading and CK, but a significant difference between74%-shading and CK.2. The ASP content in grains changed as W model during rice grain filling. The low-light increased the ASP content in grains. There was no significant difference of ASP content in IR72grains between49%-shading,74%-shading and CK, but a significant difference of ASP content in Koshihikari grains between49%-shading,74%-shading and CK.3. The ALA content in IR72grains changed as a diauxie curve during rice grain filling, which changed as an unimodal curve in Koshihikari grains. The low-light increased the ALA content in grains. There was no significant difference of ALA content in IR72grains between49%-shading,74%-shading and CK, but a significant difference of ALA content in Koshihikari grains between49%-shading,74%-shading and CK.4. The relative content and the absolute content of mature grain of the GLU and ASP and ALA increased by low light in rice grain-filling, the relative content of GLU, ASP and ALA were significantly or very significantly higher than the control,the absolute content was no significant difference with the control.5. The GS activity in sword leaf and grains changed as diauxie curve during rice grain filling. The low-light decreased GS activity, without any change of the pattern of GS activity. There were no significant difference of GS activity in sword leaf and grains between49%-shading and CK, but a significant difference of The GS activity in sword leaf and grains between49%-shading and CK.6. The GOG AT activity in sword leaf changed as an unimodal curve during rice grain filling, which gradually declined in grains. The low-light increased GOGAT activity in sword leaf, but decreased GOGAT activity in grains. There was no significant difference of GOGAT activity in sword leaf and grains between49%-shading,74%-shading and CK.7. The AST activity in sword leaf and grains of two rice varieties changed as no pattern during rice grain filling. The low-light decreased AST activity. The AST activity in sword leaf significantly decreased under49%-shading and74%-shading. There were no significant difference of AST activity in grains between49%-shading and CK. The AST activity in Koshihikari grains significantly decreased under74%-shading, without any significant difference of which in IR72grains.8. The AK activity in grains changed as an unimodal curve during rice grain filling. The low-light inecreased AK activity. There was no significant difference of AK activity in grains between49%-shading and CK, while it significantly increased under74%-shading.9. The ALT activity in sword leaf changed as an unimodal curve during rice grain filling, and of which in grains gradually decreased. The low-light decreased ALT activity without changing its pattern. There were no significant difference of ALT activity in Koshihikari grains, IR72sword leaf and grains between49%-shading and CK. The ALT activity in grains extremely significantly decreased under74%-shading.10. The improvement of GOGAT activity in sword leaves under the low-light in rice grain filling is benefit for the transport and remobilization, which implied that the increase of amino acids may owe to the no suppression of nitrogen transport under low-light. The AK activity in grains increased as well as the light covering level, which suggested the important regulation of AK activity in ASP accumulation in grains.