Photoactivation and Photoinhibition of the O2-Evolving Complex in Dark-Grown Spruce Seedlings

Abstract

Coniferous seedlings form highly-developed chloroplasts even during dark germination (1,2). The chloroplasts, however, cannot evolve oxygen since the assembly of the tetra-Mn cluster does not occur. The water-oxidizing complex in PS II membranes isolated from dark-grown spruce cotyledons can be assembled in vitro (3), as reported with NH2OH-treated PS II membranes from wheat leaves (4). This indicates that the light-induced assembly of water-oxidizing complex (photoactivation) in the dark-grown spruce cotyledons does not require de novo protein synthesis.