Pulasan [(Nephelium ramboutan-ake (Labill.) Leenh.] fruit trees: variations in flower morphology, and associated differences in pollination type

Pulasan (Nephelium ramboutan-ake) is a species of Sapindaceae which has hermaphrodite and staminate flowers on different trees. Morphological flower structures and pollination types of the pulasan fruit tree have not previously been reported thoroughly. This study was undertaken to observe the reproductive structure of flowers, and to examine its correlation with pulasan pollination type. A total of 67 hermaphrodite and 14 male trees of pulasan were observed. Some hermaphrodite inflorescences were covered using cloth bags for between four and six weeks to calculate number of fruit, and to determine their pollination system. The number of individual flowers per inflorescence on male pulasan trees was higher than for hermaphrodite ones. Panicles and spikes were found on both types of pulasan inflorescence. Flowers having four sepals was the commonest structure in both flower types. However, five stamens were commonly found in hermaphrodite flowers, while male flowers often had six. In general, stigma were curved in shape, with modification in some flowers. Anther of hermaphrodite pulasan flowers naturally never open, although their pollen is viable, so there is a mechanical barrier for self-pollination. It was concluded that pulasan tends to be an allogamous plant.