Cleistogamy in Griffithella hookeriana (Podostemaceae)

Abstract

Floral phenology, flower morphology and pollination biology were studied in Griffithella hookeriana, an endemic and poorly known species. Here we show that pollination is typically cleistogamous and the species is an obligate inbreeder. The flowers lack petals and sepals. The essential organs are covered by a spathe, surrounded by 2 or 3 pairs of bracts. The two anthers that are borne on a forked filament are placed adjacent to the globular ovary. A pair of staminodes arise from the base of the anther filament. The style is absent and the ovary bears two spoon-shaped stigmatic lobes at the apex. Pollination occurs before anthesis. This is affected by close proximity of the stigmatic lobes and the anthers and en masse transference of pollen grains (that occur in pairs, dyads) to the stigma. A large number of pollen grains germinate on the stigma and the pollen tubes enter the ovules 16–18h after pollination. Fruits are anisolobous, stalked and rounded and dehisce by means of an oblique slit. The average number of seeds per fruit is 115 ± 43.4. Flower to fruit ratio is close to 1:1 and the ovule to seed ratio is 3:1.