Reproductive biology of Dipterocarpus indicus Bedd.- An endangered species from Western Ghats, India

The Dipterocarpus indicus Bedd. is one among the dominant tropical evergreen tree species of the family Dipterocarpaceae, that grows upto a height of 37m or more. The tree is popularly known for timber and oleoresin and, it is one of the major habitat for the critically endangered lion-tailed macaques, among the other associated tree species such as Diospyros candolleana, Holigorna grahamii, and Parsea macrantha. The tree is endemic to Western Ghats region of India with a threat status as endangered at global level. The flowering is irregular, but mass flowering occurs once in every 4-7 years. The flower initiation was observed from last week of December 2012 and continued until first week of January 2015. The flowers are borne on conspicuous drooping axillary racemes. The flowers are hermaphrodite, actinomorphic and complete. Corolla with a twisted aestivation, showing five white petals bears a pink strip in the middle. The peak flower anthesis observed between the 08:00 to 10:00 hours. The pollen production was quantified to be 264.78+-59.21 and 12420+-59.21 per anther and flower respectively. Ovary is superior, syncarpous, with three locules each containing two ovules arranged in axile placentation. The observations on pollinators revealed that no biotic vectors are involved in pollination and the flowers are adopted to wind pollination mechanism. Breeding experiments revealed that the flowers are self-compatible and pollinated by means of both self and cross pollination. The manual cross pollination yielded highest fruit set (69.53+-1.77%), followed by manual self-pollination (59.77+-2.88%) and open pollination (56.95+-2.98%). The paired t-test between manual cross and selfpollination, and open pollination with manual cross were significant (p not hreater than 0.05) revealing the importance of pollinator species in bringing out successful fruit set. The controlled experiments also revealed the absence of apomixis. The natural self-pollination and less abundance or the absence of pollinators is likely to lead to inbreeding depression and impulse it more prone towards critically endangered category.