Adaptive strategies of reproduction in tropical fruit trees

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To clarify the adaptative strategies of reproduction system in tropical fruits, the following four items were investigated ; (1) seasonality of flowering, (2) floral structure in relation to pollination and fertilization, (3) self-incompatibility and apomixis, and (4) fruit setting potential1. Climatic condition, especially rainfall in Thailand was closely related to growth cycle in seasonal fruiting species but no clear relationship between them was found in Indonesia Artificial regulation of flower induction for off-season fruit production was demonstrated in commercial orchard by application of growth-regulators under adequate soil moisture control. Chlorates application specifically induced flowering of longan fruits in Thailand, which is now commercially used for off-season fruit production.2. Developmental processes and unique features of floral structure in main tropical fruit species of Southeast Asia origin were investigated in detail. The system of pollination and fertilization and the role of vector insects were also described. It revealed that there seem to exist many fruit species whose floral structure and mode of flowering fit to form seeds by cross pollination.3. No clear self-incompatibility was found in two Durian cultivars in terms of pollen tube behavior in the styles after self- or cross pollination, but more cultivars should be tested to generalize. Apomictic seed formation and fruit development were surveyed with mangosteen and Lanceum(langsat and duke) and an elaborate morphological observation revealed the unique feature of apomixis in mangosteen.4. As alteration of dry and rain seasons influenced development of topical fruit through soil moisture and light condition, a comparative study of photosynthetic rate and assimilate assignment to fruiting position was conducted using several tropical fruit species. Photosynthetic rate varied with species and the slow development of mangosteen was specifically related to low photosynthesis.