Reproductive ecology of a threatened medicinal plant Canscora alata (Roth) Wall

Abstract

Canscora alata (Roth) Wall. (Gentianaceae) commonly known as Shankhapushpi, is an annual herbaceous threatened medicinal plant distributed mainly in the understory of wild Sal (Shorea robusta Gaertn.) forest and demands immediate conservation measures, for which understanding of its reproductive ecology is important. We studied aspects of floral biology, reproductive phenology and the breeding systems of the plant species. While undertaking the experiments, it was found that the species is self-compatible with a greater capability of autonomous self-pollination and doesn’t depend largely on pollinators for seed sets. However, geitonogamous and xenogamous modes of reproduction were observed. In natural habitat, visitors' frequency was extremely low, and most of the time they were absent. Outcrossing is rare, but it is occasionally facilitated by the fly, Paragus (Paragus) Latreille. We observed an "open-close-reopen" flowering rhythm during the anthesis of a flower. The mode of floral development clearly indicates that autonomous self-pollination is favored by the movement of stamens, styles, and stigmas during its “open-close-reopen” pattern of flowering. The plant also exhibits a larger anisomorphic stamen, orange in color. Even though the “fail safe” mechanism is an adaptive trait seen in outcrossing plant species, we have observed it here as well. The larger anisomorphic stamen helped to pollinate in order to ensure reproductive assurance through a delayed selfing mechanism; this is a rare occurrence in autogamous species. Despite self-compatibility, the ability to produce fruits and seeds through hand cross-pollination treatments implies that the plant species follow a selfing-outcrossing strategy to assure successful reproduction in its natural habitat. We hope these findings will be useful in strategic planning for the conservation of this plant species.