不同天气条件下田间大豆光合作用日变化的研究

 田间大豆叶片光合速率的日变化进程和光合午休的有无、轻重，在不同天气条件下表现不同，并无固定模式。高湿的晴天，没有光合午休，气孔因素和叶肉因素对光合的限制都很小；高湿适温的多云天气，光合速率主要受光强制约，光强高时，光合速率受气孔因素限制，光强低时，受叶肉因素限制；低湿高温的晴天，常有午休出现，光合速率的中午降低，主要是气孔因素限制的结果，有时也出现叶肉因素限制。诱发气孔限制的生理生态因子，首先是空气相对湿度（RH）和叶片、大气间水汽压差（VPD），其次是叶温（LT）和叶片相对含水量（RWC）。

A STUDY ON THE DIURNAL VARIATION OF PHOTOSYNTHESIS OF FIELD-GROWN SOYBEAN IN DIFFERENT WEATHER CONDITIONS

The diurnal variation of photosynthesis and extent of the midday depression of photosynthesis in soybean leaves changed with weather conditions. In fine weather with high humidity, the midday depression of photosynthesis was not observed and stomatal and non-stomatal limitation on photosynthesis was not much. In humid and cloudy weather with optimum temperature, the photosynthesis rate depended on light intensity. When light intensity was high, photosynthesis rate was limited by the stomatal factor. But photosynthesis rate was limited by nonstomatal factor under low light intensity. In fine weather with low humidity and high temperature, the midday depression of photosynthesis occured and stomatal limitation was the main factor. But sometimes nonstomatal limitation was noted. Factors causing stomatal limitation were mainly air relative humidity (RH) and vapor pressure difference (VPD) between leaf and air. Effect of leaf temperature (LT) and leaf relative water content (RWC) on stomatal limitation was less.