MGHT-INDUCED ADAPTATION PROCESSES WITHIN PHOTOSYSTEM II FROM SPINACH

摘要

During evolution plants developed a variety of strategies to adapt to different environmental conditions, particularly to variances in the incident sunlight. Generally long- and short-term responses are distinguished. The former include molecular alterations in the pho-tosynthetic apparatus (acclimation) involving redox state controlled gene expression and the latter comprise state transitions or regulation of photosystem (II) efficiency. Inter alia these processes are aimed at (a) dissipating excessexcitation energy under high light (HL) to aid protection of Photosystem II (PS II) against photo-damage and (b) increasing antenna size around PS II enabling efficient light-harvesting during limiting light (low light, LL) (Allen & Nilsson 1997. Ke (2001)). Spinach was used as a model plant for exploring such light induced adaptation processes. After cultivation under different light intensities in a climate chamber we examined the polypeptide/chromophore composition of both photosystems in detail andtested their photochemical and oxygen evolving activities. The results obtained are discussed in the light of the adaptability of spinach plants to variant irradiances and possible underlying regulatory mechanisms. Henceforth our data will be compared to those of similar experiments reported earlier for Pisum sativum and recently for Arabidopsis thaliana (Bailey et al 2001, 2004, Park et al 1997).