Effects of simulated herbivory on pollen tube growth rate and siring ability in Nicotiana alata (Solanaceae) MARGARET MOLLEL* and IO SKOGSMYR Lund University, Department of Plant Ecology and Systematics, S-223 62 Lund, Sweden Abstract The environment in which a pollen donating plant grows is very important as it may influence pollen performance. Here we examine effects of herbivory on pollen performance in two cultivars of Nicotiana alata with red and white flowers. Plants used as pollen donors, were subjected to varying degrees of simulated herbivory and were compared to control plants. We grew pollen from all individuals in vitro to evaluate inherent male competitive ability. Hand pollinations were made to study the effects of simulated herbivory on in vivo siring ability, which in turn is the result of interactions between both the male and the female reproductive functions. Herbivory had an impact on both in vitro and in vivo pollen performance. In both cultivars, in vitro pollen tube growth rate from the control plants was higher than that in pollen from moderately and highly treated plants. The siring ability of the red cultivar decreased with increase in herbivory intensity, while the white cultivar was positively affected. The differences found between the two cultivars suggest that the genotype of the pollen grain influences how pollen from individual plants reacts to different environmental factors.   < back .