Evolution, 47(4): 1080-1093 (Aug 1993),
Pollen Aperture Polymorphism and Gametophyte Performance in Viola diversifolia

Isabelle Dajoz, Irene Till-Bottraud, Pierre-Henri Gouyon

Abstract. Pollen aperture polymorphism is studied in Viola diversifolia, where all plants produce three- and four-apertured pollen grains. We tested whether there are genetic differences among plants for the proportions of the different pollen morphs, and whether the morphs differ in gametophytic performance. Results show that the more apertures a pollen grain has, the more quickly it germinates but that few-apertured pollen grains have faster growing pollen tubes and longer life expectancies. The proportions of the different pollen morphs, together with pollen tube growth rates, may be inherited traits based on differences among matemal families. These results suggest that the different pollen morphs are favored in different pollination ecology situations. The production of several pollen morphs by the same individual could therefore be evolutionarily advantageous.

Environmental factors (and/or stress) also influence pollen vigor. In wild radish, pollen from control plants sire more seeds than pollen from stressed ones, even though stressed plants and controls show no significant differences in pollen size (Young and Stanton 1990).