Development of photochemical activities in mesophyll and bundle sheath chloroplasts of C₄ and C₃ plants during seedling growth

Abstract

The photochemical activities of mesophyll and bundle sheath chloroplasts from Setaria italica, a NADP malic enzyme type C₄ plant, were examined during seedling growth and were compared with the pattern of mesophyll chloroplasts from Oryza sativa, a C₃ plant. The sheath chloroplasts of S. italica possessed remarkable activities of photosystem (PS) II mediated reactions (non-cyclic photophosphorylation, ferricyanide and NADP reductions) at early stages. They lost much of their PS II but retained PS I activity (cyclic photophosphorylation, NADP reduction with dichlorophenol indophenol-ascorbate) during seedling growth. Mesophll chloroplasts of S. italica developed both PS I and PS II. However the mesophyll chloroplasts of both S. italica and O. sativa were similar in that PS I activity was greater in younger leaves while older leaves possessed more PS II.