Pollination of two dioecious plants: Mercurialis annua L. (Euphorbiaceae) and Bryonia dioica L. (Cucurbitaceae)

Abstract

Dioecy ensures cross pollination but pollen must travel from male to female plants, sometimes covering long distances. The present study concerns the reproductive strategy of two Italian dioecious plants: Mercurialis annua L. and Bryonia dioica L. The former is anemophilous and the latter is entomophilous; the latter has nectar and pollen as rewards. The distribution of pollen grains on the stigma is very different in the two species, reflecting the different types of pollination. In both species there is a number-dependent mechanism of pollen germination on the stigma. This mechanism could enhance male gametophytic competition.

Keywords:

• Mercurialis annua
• Bryonia dioica
• pollen deposition
• pollen germination