SELF-POLLINATION SHORTENS FLOWER LIFE-SPAN IN PORTULACA-UMBRATICOLA HBK (PORTULACACEAE)

I compared median Lifespan of exogenously unpollinated, hand self-, an d hand cross-pollinated flowers of partially autogamous Portulaca umbr aticola. Self-pollination consistently shortened flower lifespan in co mparison with either cross-pollination or absence of hand-pollination. Median flower lifespan of cross-pollinated flowers did not differ fro m the median lifespan of unpollinated flowers. Seed set was greatly in creased following hand-pollination but did not show significant differ ences between self- and cross-pollination treatments. Nevertheless, ea rly self-pollination in natural populations of this species could lead to pollen limitation, a decrease in opportunities for outcrossing, an d/or a decrease in pollen export by causing premature flower senescenc e of already short-lived flowers.