14. Pollination Biology of Sandalwood

In this chapter, we focus on the current status of knowledge on the floral biology of Santalum album and the role of flower visitors in its pollination and fruit set. Flowers are bisexual, actinomorphic and epigynous, borne on axillary or terminal panicles. Based on the position of stigma, three types of flowers are observed: pin (stigma above the level of anther), thrum (stigma at a lower level) and homostylous (stigma and anther at the same level). A flower lasts for about three days, and its colour gradually changes from pale green or white to dark red with age. Though the ovary has 2‒4 embryo sacs, only one matures. From flowering to fruit maturation, it takes 80‒85 days, and the berries are eaten by birds, especially the Asian Koel, which may also be involved in the dispersion of seeds. There appear to be some contradictions concerning pollination, though many workers suggest that S. album is an obligate outcrossing species. However, the per cent fruit set under open pollination conditions appears to be very low, indicating a deficit in pollinators. Of the 46 species of flower visitors recorded, syrphids, calliphorids and honey bees have been reported as the most frequent visitors. However, there have been no studies to identify efficient pollinators, as most of the reports are subjective and are not supported by hard data. We also discuss the methods to be followed in sandalwood pollination studies.