FLOWER DEVELOPMENT AND MALE-STERILITY IN OCOTEA-TENERA (LAURACEAE) - A GYNODIOECIOUS TROPICAL TREE

Androecium development and gynoecium development were compared among h ermaphroditic flowers from non-fruiting (NF) and low-fruiting (LF) tre es and female flowers from high-fruiting (KF) trees of gynodioecious O cotea tenera Met & J.D. Smith ex Met. Dramatic qualitative differences in androecium development were identified between gender classes. Ant hers in all flowers initiated microsporogenesis, with flowers from NF and LF trees eventually producing pollen, although some pollen from LF trees was slightly malformed. In anthers from HF trees, pollen develo pment terminated after microspore tetrads developed, and the immature pollen grains eventually degenerated. Allometric relationships between flower growth and gynoecium growth differed among gender classes, wit h flowers from HF trees having a significantly greater slope. Allometr ic relationships between androecium and whole-flower growth were not d ifferent, but androecium size was reduced in female flowers. We argue that the gene, or genes, causing abortion of pollen grains in flowers of HF trees not only causes male sterility but also has a cascade of e ffects on stamen and corolla development. In contrast, gynoecium devel opment appears to be uncoupled from androecial and corolla development . The uncoupling may allow natural selection to shape specific structu ral attributes of female flowers and functionally male flowers separat ely.