温州蜜柑叶片光系统反应中心光能分配的变化

为深入了解果树光化学反应中心光能分配的状况，以柑橘为试材，采用调制荧光法对叶片光系统在高光强和低光强下的状态转换进行了研究．结果表明，光系统在100μmol·m^-2·s^-1的低光强下，由于QA的还原使PQ库处于还原状态，导致光能由PSⅡ转向PSⅠ分配，光系统处于状态2；在1000μmol·m^-2·s^-1的高光强下，PQ库无法得到电子而处于氧化状态，导致光能分配由PSⅠ转向PSⅡ，光系统处于状态1，叶片经磷酸酯酶抑制剂NaF处理后，光系统从高光强下状态2到状态1的转换受到抑制，高光强下过多的光能由PSⅠ向PSⅡ分配是导致PSⅡ光破坏的重要原因．

Changes of light energy distribution in reaction centers of Citrus unshiu leaf photosystem under different light intensities

In order to further understand the light energy distribution in photochemical reaction centers of fruit trees, this paper employed modulated fluorescence technique to study the state transition of photosystem in Citrus unshiu leaves under high and low light intensities. The results indicated that under low light intensity of 100 micromol x m(-2) s(-1), the PQ pool was in reduction state due to Q(A) reduction, which made the light energy distribution in photosystem changed from PS II to PS I; while under high light intensity of 1000 micromol x m(-2) s(-1), the PQ pool could not get electron and was in oxidation state, making light energy distribution changed from state 2 to state 1. When the leaves were treated by a phosphatase inhibitor NaF, the state 2 to state 1 transition of photosystem was inhibited under high light intensity, and the excessive light energy distribution from PS I to PS II caused damage to PS II. These findings would be helpful to understand the mechanisms of the photoinhibition of photosynthesis and the photodamage of photosynthetic apparatus of fruit trees.