Amitrole effects on barley etioplasts.

The effects of aminole-inhibited carotenogenesis on the differentiation of etioplasts have been investigated in barley plants grown either at 20·C or 30·C in darkness. Amitrole drastically impaired carotenoid synthesis in plants grown at 20·C and this effect was paralleled by extensive ultrastructural alterations in the etioplasts. Protochlorophyllide oxidoreductase was found in the badly arranged membranes together with abnormally high quantities of protochlorophyllide, essentially present as non-phototransformable pigment. Growing plants at 30·C caused a remarkable improvement in the carotenoid synthesis, which was accompanied by a normalization of all the other parameters analysed. The parallelism observed between correct carotenoid synthesis and normal etioplast development suggests that, as in chloroplasts, also in the dark-grown organelles, the carotenoids carry out a structural function, playing a role in the establishment of the regular organization of the inner membrane system.