Stigma Secretion in the Watermelon Before and After Pollination

Abstract

The production and histochemistry of the secretion of the unpollinated and pollinated watermelon stigma were followed from 6 days before to 1 day after anthesis Stigmatic secretion occurred during the 2 days prior to anthesis. The secretion contained lipid, carbohydrate, and water with protein confined to its outer surface. No further secretion was produced by the unpollinated stigma. Pollination of the stigma at anthesis resulted in a rapid stimulation of stigmatic secretion. The new secretion was present at 10 min after pollination, and by 30 min the papillae and pollen grains were submerged in the secretion. No further secretion occurred after 30 min following pollination. We suggest that the increase in stigma secretion in response to pollination ensures sufficient medium for the hydration and germination of a large number of pollen grains.