Effect of Floral Size Reduction on Pollination and Reproductive Efficiency of Female Flowers of Valeriana wallichii, a Threatened Medicinal Plant

Abstract

Valeriana wallichii DC. (Valerianaceae), a threatened medicinal plant of Himalayan region, has individuals showing 3 patterns of sex expression (female, hermaphrodite, and gynomonoecious). In the present study, the effect of floral size reduction on pollination efficiency of female flowers on female plants of Valeriana wallichii has been determined. To check entomophily as the possible mode of pollination, plants growing in nature are monitored whether or not the flowers are visited by some insects. Apis dorsata and Apis cerana are observed to be the main pollinators of this species. Female plants receive less pollinator service as compared to hermaphrodite plants. Reduced floral size in females offers more number of stigmas to get pollinated in a single visit as greater number of flowers get in contact with the visiting insect. The time of stigma receptivity also varies in female and hermaphrodite flowers. In females, it remains receptive for longer duration. Further, the pollen load on stigmata of open pollinated hermaphrodite as well as female flowers is studied. It is experimentally demonstrated that at the end of the season, the amount of pollen load is lesser in females as compared to hermaphrodites. Reproductive output of both types of individuals is estimated, and seed germination experiments are performed. Reproductive output and seed germination are more in females.