Photosystem II Activity in Agranal Bundle Sheath Chloroplasts from Zea mays

Abstract

The photochemical activities of chloroplasts isolated from bundle sheath and mesophyll cells of maize (Zea mays var. DS606A) have been measured. Bundle sheath chloroplasts are almost devoid of grana, except in very young leaves, while mesophyll chloroplasts contain grana at all stages of leaf development.Chloroplast fragments isolated from bundle sheath cells showed a light-dependent reduction of potassium ferricyanide, 2, 6-dichlorophenolindophenol, mammalian cytochrome c, plastocyanin, and Euglena cytochrome c(552). These activities were inhibited by 3-(3, 4-dichlorophenyl)-1, 1-dimethylurea at 1.25 micromolar. However, the photoreduction of NADP from water was extremely low or absent, except in chloroplasts from very young leaves, and the capacity for NADP reduction appeared to be related to the degree of grana formation.Photosystem I activity was present in bundle sheath chloroplast preparations at all stages of leaf growth and senescence examined. However, the activity was lower than in isolated mesophyll chloroplasts. NADPH diaphorase activity was comparable in both types of chloroplast.Chloroplasts isolated from bundle sheath cells of plants grown under a variety of conditions, including continuous and intermittent light, high and low light intensities, and high temperature, exhibited photosystem II activity.