Floral reproduction biology of Desmos chinensis Lour. (Annonaceae)
2004
Ng, A.K.W.E-mail:[email protected] | Saunders, R.M.K.(The Univ. of Hongkong, Pokfulam Road, Hongkong (China). Dept. of Ecology and Biodiversity)
There are comparatively few experimental studies of the pollination ecology and breeding systems of Annonaceae species, particularly from the palaeotropics. The present research involves a detailed study of Desmos chinensis Lour from Hongkong. The flowers are hermaphroditic, and have two whorls of three petals; each petal is yellow at maturity, and is basally clawed. The petals separate early in development, exposing the immature reproductive organs; the three inner petals subsequently cohere, however, forming a largely enclosed pollination chamber around stamens and carpels, with small apertures adjacent to the basal claws of each petal. The flowers are protogynous, and are receptive over a 2-day period. The stigmas become receptive (with light exudate, without odour) at around 19:00 hrs on day 1; this pistillate phase continues for c. 24 hrs, and between 19:00-20:00 hrs on day 2 is correlated with the emission of a strong 'fruity' scent and sticky stigmatic exudate. The staminate phase (with anther dehiscence) subsequently begins at around 12:00-02:00 hrs between days 2 and 3, and is followed by abscission of stamens. Elevated internal temperatures were also recorded in both reproductive phases: this thermogenesis presumably assists with the volatilization of aromatic compounds. Small beetles were observed in the floral chambers during both the pistillate and staminate phases; pollen of D. chinensis were observed adhering to the bodies of the beetles, indicating that the beetles are effective pollinators. Controlled pollination experiments indicate that the species is largely xenogamous, and that flowers bagged to exclude pollinators did not result in seed-set.
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