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Pollination in Barringtonia
Chih-Hua Tsou (08-16-2005)
A blooming inflorescence of Barringtonia racemosa being visited by many moths was beautifully recorded by Tzong-Hsien Chen on the campus of Academia Sinica at midnight of July 20.
Barringtonia racemosa (Fig. 1) and B. asiatica are the only two species of Lecythidaceae native to Taiwan. Both species are mangrove associates (i.e., they are well adapted to intertidal environments); nevertheless, they grow well in terrestrial habitats.
Flowers of Barringtonia racemosa have the typical syndromes of moth pollination: anthesis at night, petals white, androecium brush-like (the male part, composed of numerous slender stamens), and producing nectar. Figure 1 shows more than 7 moths visiting the inflorescence searching for the nectar. The one at the lower right is fairly large, while the others are much smaller. Only moths are able to touch both the pollen sac and the tip of style (i.e., able to transfer pollen grains [Figs. 2, 3] to the female receptive surface), are the effective pollinators. The remaining moths are visitors or simply nectar thieves.
Barringtonia belongs to the Old World subfamily Planchonidoideae. The 6 genera of Planchonioideae have similar floral syndromes as those of Barringtonia racemosa: radial symmetrical, androecium brush-like, and producing nectar. The other major subfamily, Lecythidoideae, has 10 genera distributed in the New World.
Floral syndromes of Lecythidoideae are much diversified, and the most have bisymmetrical flowers with a highly specialized male part (Fig. 5), which promotes more specific interactions between the plant and its pollinators.
Figures 4 and 5 display the plant, flowers, and fruits of Couroupita guianensis, the famous "cannon ball tree". This species has amazing gross morphology: the long-lasting inflorescences sticking out of the trunk, the fruits cannon ball-like, and the flowers with a prolonged and showy androecium. The developmental process of such a unique and beautiful flower is currently being studied by Chih-Hua Tsou. |
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