籽粒蛋白质含量不同的小麦品种间光合速率的比较

Comparison of Photosynthetic Rates of Wheat Cultivars with Different Levels of Grain Protein Content

用 15个蛋白质含量和产量均有较大差异的小麦品种为试材 ,分别测定了以CO2 同化速率和光合放氧速率为指标的光合作用状况。相关分析表明 ,苗期以CO2 同化速率表示的光合速率与籽粒蛋白质含量之间呈极显著负相关关系 (r =- 0 .75 ) ,与籽粒产量则达极显著正相关关系 (r=0 .84 9 ) ;以光合放氧速率表示的光合速率与籽粒蛋白质含量之间呈显著正相关 (r =0 .5 15 ) ,而与产量无相关关系 (r =0 .4 15 )(图 1)。用CO2 同化速率和光合放氧速率对品种所作的聚类分析表明 ,15个品种被明显分为两个大类 ,一是光合放氧速率较高而CO2 同化速率较低 ,另一类则相反 (图 2 )。蛋白质含量高的品种其CO2 同化速率较蛋白质含量低的品种低 ,但光合放氧速率却不低 ,甚至高于蛋白质含量低的品种。籽粒形成期间 ,蛋白质含量高的品种光合CO2 同化速率和光合放氧速率下降幅度相对较小 ,后期衰老较慢 (图 3) 。

Photosynthetic rates in terms of CO 2 assimilation and O 2 evolution in 15 wheat cultivars different both in grain yield and protein content were measured at their seedling stage and during the grain filling period. At seedling stage, the correlation coefficients between CO 2 assimilation rate and protein content ( r C P ) and grain yield ( r C Y ) were - 0.75  (Fig.1B) and 0.849  (Fig.1A), respectively, whereas photosynthetic O 2 evolution rate was positively correlated with their protein content ( r O P =0.515 , Fig.1D). Cluster analysis(Fig.2) shows that high protein content cultivars mostly had a comparatively low CO 2 assimilation rates, while photosynthetic rates measured in terms of O 2 evolution were not lower and,in some of them, were even higher than low protein content cultivars. During grain filling period, CO 2 assimilation and O 2 evolution rates in high protein content cultivars declined more slowly than that in the high yielding cultivars. Such cultivars also senesced slowly(Fig.3), which was probably resulted from their relatively high nitrogen content and nitrate reductase activity in leaves.