大豆光合午休原因的分析

研究了大豆光合午休过程中有关生理生态因素与光合速率的函数关系，并对叶温、叶片-大气水汽压亏缺（VPD）、气孔导度与光合速率之间的关系进行了通径分析。结果表明在光合午休的13：00时与15：00时这两个时刻，光合速率与VPD、叶温和气孔阻力呈极显著负相关，15：00时光合速率随VPD和叶温上升而下降的速率要大于13：00时的下

Analysis of Causes of Midday Depression of Photosynthesis in Soybean Leaves

The relationship between related physiological and ecological factors and photosynthesis during midday depression of photosynthesis in soybean leaves were studied. The path analysis was also used to estimate the effects of Leaf temperature (TL),leaf to air vapour pressre deficient (VPD) and stomatal conductance (Cs) on photosynthesis (A). The TL, VPD and stomatal resis-tance (Rs) are significantly nagatively correlated with photosynthesis at 1:00 PM and 3:00 PM during midday depression of photosynthesis. At 3:00PM as VPD and TL increase photosynthetic rate decrease more pronouncely than that at 1:00PM, however as Rs increase photosynthetic rate decrease more pronouncely at 1:00PM than that at 3:00PM. The path analysis indicate that at different times during rnidday depression of photosynthesis the dominant factors of depression of photosynthesis are different. At 11:00AM the decrease of Cs is the main cause of the depression of photosynthesis, while the direct effects of VPD and TL on A are almost ineffec-tive. At 1:00PM and 3:00PM the high VPD and TL become dominant factors of depression of photosynthesis. The direct effect of Cs on A is almost ineffective at 3:00PM, however, the stomatal coductance has remarkable indirect effect on depression of photosynthesis by influencing VPD and TL at 1:00 PM and 3:00 PM.