Temporal changes of floral nectar-sugar composition in Polyscias sambucifolia (Sieb. ex DC.) Harms (Araliaceae)
1994
Gillespie, L.H. | Henwood, M.J.
Polyscias sambucifolia (Sieb. ex DC.) Harms, an endemic Australian species 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 sexual phases. This study characterised the changes of the major nectar-sugars secreted in each sexual phase. The implications of such shifts in nectar composition with respect to the morphological dissimilarity of the two sexual phases are considered. Field based sampling with HPLC analysis was employed to characterise the major sugar content of nectar. During flowering, nectar consisted of equal amounts of fructose and glucose, with negligible amounts of sucrose. There was statistically significant variation in the concentration of fructose and glucose in each sexual phase. Male phase nectar had approximately 6% of the sugar concentration of the female phase nectar in hermaphrodite flowers. The effect of pollination upon nectar secretion was also investigated. Hand pollinations resulted in an attenuated nectar secretion duration and the production of nectar with a reduced sugar content.
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