Variegation in Selaginella martensii f. albovariegata. II. Plastid structure in mature leaves

Abstract

Mature green, variegated, and white leaves of Selaginella martensii f. albovariegata were examined by light and electron microscopy. Paraffin sections show the anatomy of all three leaf types to be comparable with that reported for wild type S. martensii. With the light microscope, chloroplasts in green cells appear identical with those of the wild type, while plastids in white cells are smaller and less regular in shape. Chloroplast ultrastructure in green cells is comparable with that described for S. martensii and other members of the genus and quite similar to that typical of seed plants. Plastids of white cells display many structural defects. Large portions of the plastid volume are occupied by vacuoles. In variegated leaves these plastids possess sparse internal membrane systems consisting primarily of irregular vesicles distributed throughout the stroma. In white leaves single lamellae and sets of aligned lamellae are associated with many of the plastid vacuoles. The plastid defects suggest a high susceptibility to photooxidative bleaching.