Spatial and temporal variation in pollen tube numbers in Lindera benzoin (spicebush)

Abstract

The numbers of pollen tubes per stigma and style were examined in naturally pollinated plants in two populations of the dioecious shrub Lindera benzoin to reveal variation between populations, among plants within populations, among flowers within plants, and among early and late blooming flowers. Most of the variation in pollen tube numbers is within individual plants. Differences between populations are likely due to observed differences in pollinator activity. Flowers that opened later in the flowering season were more likely to be pollinated and had larger numbers of pollen tubes per stigma than those that opened earlier. The level of variation observed among stigmas diminished as pollen tubes entered the style indicating that pollen–stigma interactions may be important in the fertilization process. Even under conditions of low pollen deposition and pollinator activity, pollen tube competition may still occur. Key words: Lindera benzoin, pollen tube, pollen–stigma interactions.