EFFECTS OF WATER STRESS ON PHOTOCHEMISTRY AND ON THE THERMOTOLERANCE OF PHOTOSYSTEM II IN WHEAT PLANTS

摘要

In response to a water stress, a decrease in net CO_2 assimilation is generally observed. Despite great progress in understanding the effect of water stress on photosynthesis, there is still no unified concept of the events which reduced photosynthetic efficiency (Lawlor 2002). In particular, PSII has been shown to be very sensitive to water stress. In vivo studies demonstrated that water stress resulted in damage to the oxygen evolving complex of PSII and to the PSII reaction centers (Havaux et al 1987, He et al 1995). On the other hand, other studies have shown that PSII photochemistry is hardly affected by water stress (Cornic & Fresneau 2002). In contrast, the photosynthetic apparatus, and particularly PSII, is known to be sensitive to heat stress (Yordanov 1992). In addition, it has been shown that water stress enhanced the thermostability of PSII (Havaux 1992).