Intra- and Inter-specific Pollination of Santalum spicatum and S. album

Abstract

The flower morphology, receptivity and sexual compatibility between genotypes and species were determined in Western Australian sandalwood (Santalum spicatum) and Indian sandalwood (S. album). The results showed that the stigma of both species became receptive at anthesis and reached a peak at 3 or 4 days after anthesis. Pollen tubes took 2 days to grow to the ovary when pollinated at anthesis, and 1 day when pollinated 2 or 3 days after anthesis. The egg apparatus matured at least 2 days after pollination and varied between genotypes. Fertilisation occurred 2 or 3 days following cross pollination. Although 10–40% of ovules were fertilised following intra-specific crosses of both species, the average initial fruit set was much lower: 4% in S. spicatum and 19% in S. album. Most immature fruit (75–80%) abscised following intra-specific pollination. The number of pollen tubes that grew in styles after self-and inter-specific pollination was lower than that for intra-specific pollination. Following self and inter-specific pollination, growth of pollen tubes was arrested in the style, ovary and around the embryo sac; a few penetrated the embryo sac. Initial fruit set was low and developing fruit abscised prematurely. The results indicated that pre- and post-fertilisation mechanisms control self-incompatibility and inter-specific incompatibility between the sandalwood species.