Recovery from Low Temperature Photoinhibition Is Not Governed by Changes in the Level of Zeaxanthin in Rice (Oryza sativa L.) Leaves

Abstract

Summary The possible involvement of zeaxanthin (Z) in the recovery of photochemical efficiency of photosystem II (PSII) from chilling-induced photoinhibition in rice ( Oryza sativa L. cv. Dongjin-byeo) leaves was investigated. During recovery at 20°C after chilling in moderate light, the increase in PSII efficiency was biphasic. The first phase of recovery was mainly due to the relaxation of the trans-thylakoid proton gradient. The following second phase was insensitive to nigericin and accompanied by a decrease in the level of Z. However, incubation with salicylaldoxime, an inhibitor of epoxidase, blocked Z epoxidation without any effect on PSII recovery. During recovery at 10°Q the amount of Z continued to decline after the PSII efficiency had reached a constant level corresponding to the first phase of recovery at 20°C. When leaves were allowed to recover at a photosynthetic photon flux higher than 30 emol. m −2 · s −1 , both the decrease in the content of Z and the increase in PSII efficiency were slowed down. However, dithiothreitol eliminated the retarding effect of light on the rate of Z decrease while exerting little effect on PSII recovery. In high light-chilled leaves, pretreatment with lincomycin blocked both the increase in PSII efficiency and the decrease in the level of Z during recovery in the light, but lincomycin only marginally affected the Z epoxidation during recovery in the dark. It is concluded that the recovery of PSII efficiency from low temperature photoinhibition is not mainly controlled by changes in the level of Z in rice leaves. The possible indirect links between Z epoxidation and PSII recovery from photoinhibition are discussed.