The action of 2, 21 and 100% of oxygen on primary photochemistry of photosystem II (PS II), biosynthesis of pigments and carbon dioxide fixation by etiolated bean leaves during greening

Abstract

SynopsisThe responses of photosynthesis to oxygen concentration 2, 21 and 100% by etiolated bean leaves upon illumination were determined. After 0.3, 3, 6, 10, 12 and 24 h of greening the following processes were measured. (1) Functioning of PS II as reflected by changes in Fv/Fm ratios and t1/2 values. (2) Content and composition of pigments. (3) Capacity for carbon dioxide assimilation. The results showed that O2 exerts a complex inhibitory action on examined processes. The magnitudes of inhibition increased with increasing of O2 concentration and time of its action. Under applied conditions the lag phase for development of examined processes (with the exception of carotenoids) was in the range 3-10 h. After 24 h of greening in 2, 21 and 100% of O2 the Fy/Fm ratios attained values 0.55, 0.45, 0.13 respectively as compared with typical 0.80 of normal green leaves of bean. After 24 h of greening the inhibition by 100% O2 as compared with zero inhibition by 2% O2 were, in percentages: Fw/Fm, 78; t1/2, 77; chlorophyll a, 59; chlorophyll b, 69; β-carotene, 78; neoxanthin, 60; zeaxanthin, 43; violaxanthin, 35; CO2 fixation, 95.