Abstract
Photoinhibition of photosynthesis was studied in Vicia faba leaf discs at chilling (4oC), room (25oC) and high (40oC) temperature under 2000 *mole quanta m-2s-1. Quantum efficiency of PS II (FV/FM) showed a linear time dependent decrease at room temperature. The decrease was further enhanced at chilling temperature and maximum at high temperature.
The far-red (FR) light (13.5W.m-2) induced *I/I0 at 830nm (P700+FR) and FR+SP (saturating-pulse) induced P700+TOT in vivo, decreased with photoinhibition. High temperature treatment accelerated the decrease in P700+FR and P700+TOT in darkness. High light accelerated the decrease in P700+FR but caused no significant change in the P700+TOT compared to that in darkness at room temperature, suggesting that P700 pool could not be fully oxidised during photoinhibition at room temperature. However, chilling temperature caused severe damage (*80%) to P700+TOT. This study shows a characteristic difference in the temperature dependent changes in PS I activity under photoinhibitory condition.
