水稻低叶绿素含量突变对光合作用及产量的影响

突变体水稻叶绿素含量仅是其野生型水稻的51%，但是其饱和光合值在低氮、中氮、高氮处理下，却比对照野生型水稻分别高3.7%、20.4%与39.1%。为了探究其生理学机制，分别在大田与盆栽试验中，不同氮肥水平研究了突变体材料与野生型材料的叶片Rubisco酶含量、气孔导度、水通道蛋白表达水平、叶绿素荧光、叶片解剖结构和叶绿体超微结构。叶绿体超微结构表明突变体材料虽然叶绿素含量降低，叶绿体的发育并未受到影响；叶绿素荧光试验结果表明，高光强下，低叶绿素含量突变体并未受到光抑制，光反应电子传递未受影响。气孔导度数据、叶片显微结构观察与水通道蛋白基因表达数据表明叶黄突变体具有较高的气孔与叶肉导度；同时低叶绿素含量突变体内较高的Rubisco酶含量也是其在高光照条件下具有较高光合速率的重要原因。产量数据表明，叶黄突变体虽然生育期短，但其产量水平与对照无显著差别，这可能与其高光强条件下有较高的光合速率有关。上述试验结果表明高叶绿素含量并不是叶片高光合速率的必需条件。在今后的高光效育种中，挑选叶绿素含量适宜的品种更有利于叶片内氮素在其他光合器官中的分配，提高光合效率，最终获得高光效品种。在本研究中使用的叶绿素含量降低突变体在高光效育种中有潜在的研究价值。

Effects of the Mutant with Low Chlorophyll Content onPhotosynthesis and Yield in Rice

A chlorophyll-deficit rice mutant (YL) with ~51% chlorophyll of its wild type (WT) was 3.7%, 20.4%, and 39.1% higher in photosynthesisthan WT under saturating light condition,in treatments of0 kg N ha^-1, 120 kg N ha^-1, 240 kg N ha^-1, respectively. In the field and pot experiments, we studied leaf Rubisco content, stomatal conductance, expression levels of aquaporin genes, chlorophyll fluorescence, light and electron micrographs at different levels of N application. The results showed that the decreased level of chlorophyll content in YL was compensated by a relativelyhigher quantum yield of PSII. The electron micrographs of chloroplasts showed that there were no differences in chloroplast development between YL and WT. The stomatal conductance was much higher in the mutant than in wild type, and expression levels of the aquaporin genes suggested a higher mesophyll conductance in YL. The higherCO₂ conductance together with a higher Rubisco content in YL could be reasons for the higher photosynthetic rate. The yield of YL was similar to that of WT, but the growth duration in YL was much shorter, which could be caused by the different photosynthetic performance between YL and WT. All these results implicate that higher photosynthetic rate doesnot necessitate higher chlorophyll content. Moderate chlorophyll content will benefit the leaf photosynthesis. Decreasing N investment in chlorophyll synthesis and optimizing N distribution among different photosynthetic compounds could potentially improve photosynthesis and yield. The YL material used in this study could be potentially used to improve photosynthetic efficiency in breeding programmes.