STUDIES ON THE REPRODUCTIVE-BIOLOGY OF MELASTOMATACEAE IN CERRADO VEGETATION

Controlled pollinations and observations of pollen tube growth, pollen fertility and cytological data were studied in 11 species of Melastom ataceae growing in ''cerrado'' in SE Brazil. Seven species produced ap omictic fruits with viable seeds. Four species were not apomictic, wit h two self-incompatible (gametophytic ST) and two self-compatible, one showing spontaneous self-pollination. The apomictic species had lower pollen fertility than sexual ones -although in some cases differences were not significant -showing that low pollen fertility may be a usef ul indicator of apomixis if analysed using careful sampling supplement ed by emasculation experiments. The apomictic species also showed meio tic irregularities, probably related to hybridization, polyploidy and the cause of low pollen fertility. Apomixis in this group probably is more associated with taxonomy and phylogeny than habitat or habit, sin ce 85% of the apomictic species reported in the literature belong to t he tribe Miconieae and occur in a wide range of vegetation types and h ave diverse habits. This suggests the existence of very extensive apom ictic complexes comparable to those reported in mainly temperate gener a of Asteraceae and Rosacene.