Studies on Reproductive aspects of Willisia selaginoides (Podostemaceae), an endemic species from Kerala
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The present study deals with some aspects of reproductive biology of an endemic and endangered aquatic angiosperm, Willisia selaginoides (Bedd.) Warm. ex Willis (Podostemaceae) restricted to the Western Ghats of India. Due to its occurrence in the challenging habitats, there is limited information available on its reproductive biology. Willisia possesses a small tuft of shoots with triangular thick scales and terminal flowers. The horizontal thallus arising after seed germination is considered as primary shoot and the vertical shoots arising on the dorsal surface of the thallus are considered as secondary shoots. The gummy substance exudes from the lower elongated surface cells (rhizoids) of the shoots and holdfast help in firm attachment to the shoots to rocks in fast flowing water. The flower is enclosed in spathella and represented by a pistil with bilobed stigma and a pair of dithecous anthers. Initiation of flower buds and subsequent development occurs in submerged conditions but flowers open only after the water level lowers down after monsoon. Pollination occurs when the flowers are just exposed to air after lowering of water level at the air-water interface. Co-occurrence of stigma receptivity with anther dehiscence and the close proximity of two organs seem to promote self -pollination. The pollen:ovule ratio (32:1) and ovule:seed ratio (6:5) suggest that even after relatively low pollen:ovule ratio, chances of high seed set occur. It clearly indicates the best possibility of selfpollination.
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