Photoinhibition in chilling stressed Leguminosae: comparison of Vicia fabaand Pisum sativum

The concentrations of photosynthetic pigments decreased in both chilling st ressed species but the ratios of chlorophyll (Chl) a/b and total carotenoid s (Car)/Chls were depressed only in faba bean. The contents of alpha+beta c arotene and lutein+lutein-5,6-epoxide remained unaffected in both species, but the de-epoxidation state involving the components of xanthophyll cycle increased in pea. Under chilling stress the photosynthetic electron transpo rt associated with photosystem 2, PS2 (with and without the water oxidising complex) decreased in both plant species, the inhibition being higher in f aba bean, The intrachloroplast quinone pool also decreased in both stressed species, yet an opposite trend was found for cytochrome b(559LP). Under st ress an increasing peroxidation of thylakoid acyl lipids was detected in pe a, but higher protein/Chl ratio was detected in faba bean. Thus the accepto r side of PS2 is mostly affected in both chilling stressed species, but fab a bean is more sensitive.