OCCURRENCE OF A MIXTURE OF KETOCAROTENOIDS IN CHLOROPLAST PLASTOGLOBULES OF YOUNG LEAFLETS OF A CYCAD

An investigation was carried out on chloroplast plastoglobules in youn g leaflets of ''forma fuscoviridis'' of Ceratozamia mexicana Brongn., a cycad characterized by a transitory red-brown colour in the first st ages of developing leaves. Plastoglobules were isolated by several ult racentrifugations and the contents of the different ''rings'' were com pared on silica gel layers with natural standards obtained in our labo ratory from fully ripe fruits of Murraya exotica L. and of Triphasia t rifolia (Burm. f.) P. Wilson. (the two very rare semi-beta-carotenone and triphasiaxanthin) and from the leaflets of the same ''forma fuscov iridis'' (the novel ceratoxanthin). The results pointed out that the r ed-brown coloration is due to the presence of a mixture of eight ketoc arotenoids in the plastoglobules densely packed around the prolamellar body of young chloroplasts.