Photosystem II Activity in Agranal Bundle Sheath Chloroplasts

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 Cm2. 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.