Pollen Tube Growth and Seed Set of Banksia coccinea R.Br. (Proteaceae)

Controlled hand pollinations and field observations were usedin conjunction with fluorescence and scanning electron microscopyand fruit and seed set to investigate the timing of stigma receptivity,pollen tube growth and self-incompatibility in relation to fertilityin B. coccinea. The species showed both protandry and partialself-incompatibility. Peak stigma receptivity as measured bypollen germination was recorded at 3 d after anthesis and maximumproduction of stigmatic exudate at 6 d. Pollen tubes reachedthe base of the style by 6 d after pollination. A 5 x 5 diallelexperiment was conducted and the results measured by pollentube growth. Self-pollinations generally resulted in poorertube growth than crosses and there was significant specificand general combining ability as well as reciprocal effects.Cross-pollination resulted in improved fruit set and seed toflower ratio over both selfing and open pollination. Spatiallimitations to fertility due to infructescence size were alsorecorded, but the combination of outcrossing mechanisms andspatial limitation did not entirely account for the low fertility.It is suggested that environmental conditions and the availabilityof resources may also exert an influence. Banksia coccinea R.Br., scarlet banksia, Proteaceae, pollination, stigma receptivity, pollen tube growth, self-incompatibility, breeding system, seed set