Pollination biology and breeding system of Acacia senegal

Phenology, pollination biology and breeding system were investigated in thr ee populations of Acacia senegal located in Delhi and Rajasthan. Flowers em it a mild fragrance and produce a minute quantity of nectar. The stigma is wet non-papillate, cup-shaped and generally accommodates one polyad with 16 pollen grains. The style is solid. The mass effect created by the brush ty pe of blossoms attracts a wide variety of insects, of which the giant, Asia n honeybee, Apis dorsata, is the effective pollinator. Manual in vivo polli nation studies have shown that the species is self-incompatible. Self-incom patibility appears to operate inside the embryo sac. Under natural conditio ns fruit. set is as low as 0.36%. Insufficient pollination is the main caus e of low fruit set. Manual xenogamous pollinations substantially improve fr uit set to 30%. (C) 2001 The Linnean Society of London.