Light control of plastogenesis and ribulosebisphosphate carboxylase levels in mustard seedling cotyledons.

We have studied the problem whether the phytochrome-mediated accumulation of ribulosebisphosphate carboxylase ("carboxylase"; EC 4.1.1.39) in the cotyledons of sinapis alba L. is related to size, ultrastructure, or organization of the plastid compartment. We have shown that under different light conditions (e.g. continuous far-red light, continuous white light) which lead to conspicuously different plastids the time course of the enzyme levels remains precisely the same. It is concluded that the onset and the rate of carboxylase accumulation is not related to the organizational state of the plastid compartment as discernible under the electron microscope.