Temporal Changes of Floral Nectar-sugar Composition in Polyscias sambucifolia (Sieb. ex Dc.) Harms (Araliaceae)

Polyscias sambucifolia (Sieb. ex DC.) Harms, an endemic Australianspecies of the Araliaceae, is strongly dichogamous and andromonoecious.Petals and stamens are present only in the male sexual phase,although nectar is secreted in both the male and female sexualphases. This study characterised the changes of the major nectar-sugarssecreted in each sexual phase. The implications of such shiftsin nectar composition with respect to the morphological dissimilarityof the two sexual phases are considered. Field based sampling with HPLC analysis was employed to characterisethe major sugar content of nectar. During flowering, nectarconsisted of equal amounts of fructose and glucose, with negligibleamounts of sucrose. There was statistically significant variationin the concentration of fructose and glucose in each sexualphase. Male phase nectar had approximately 6% of the sugar concentrationof the female phase nectar in hermaphrodite flowers. The effectof pollination upon nectar secretion was also investigated.Hand pollinations resulted in an attenuated nectar secretionduration and the production of nectar with a reduced sugar content.Copyright1994, 1999 Academic Press Pollination, nectar sugar composition, fructose, glucose, sucrose, HPLC, Polyscias sambucifolia, Elderberry Panax, Araliaceae