AMITROLE EFFECTS ON BARLEY ETIOPLASTS

The effects of amitrole-inhibited carotenogenesis on the differentiati on of etioplasts have been investigated in barley plants grown either at 20 degrees C or 30 degrees C in darkness. Amitrole drastically impa ired carotenoid synthesis in plants grown at 20 degrees C and this eff ect was paralleled by extensive ultrastructural alterations in the eti oplasts. Protochlorophyllide oxidoreductase was found in the badly arr anged membranes together with abnormally high quantities of protochlor ophyllide, essentially present as non-phototransformable pigment; Grow ing plants at 30 degrees C caused a remarkable improvement in the caro tenoid synthesis, which was accompanied by a normalization of all the other parameters analysed. The parallelism observed between correct ca rotenoid synthesis and normal etioplast development suggests that; as in chloroplasts, also in the dark-grown organelles, the carotenoids ca rry out a structural function, playing a role in the establishment of the regular organization of he inner membrane system.