INTERACTIVE EFFECTS OF POLLINATION AND HEAVY-METALS ON RESOURCE-ALLOCATION IN POTENTILLA-ANSERINA L

We studied resource allocation between sexual reproduction and clonal propagation in a perennial stoloniferous clonal plant, Potentilla anse rina, an obligate outcrosser. We manipulated reproductive effort of Po tentilla anserina either by hand-pollinating all flowers or by prevent ing pollination. To test the effect of resource-limiting conditions on resource allocation and reproductive output, we used a control and tw o levels of heavy metals (copper and nickel) to limit plant growth. Th e experiment was conducted as a 2 x 3 factorial design to reveal possi ble interactions between reproductive manipulation and resource limita tion. Heavy metals decreased the total biomass of the plants and numbe r of flowers and ramets produced. Only 50% of the plants grown with th e higher level of heavy metals produced flowers. Pollination treatment interacted significantly with the heavy-metal treatment. In the metal control (no metals added) and lower heavy-metal treatment, there were no significant differences in total vegetative biomass between the tw o pollination treatments. Costs of reproduction in terms of subsequent flowering in the later season appeared to be clear, because the numbe r of flowers per whole plant was lower if the plants were hand-pollina ted and because the proportion of flowering ramets decreased due to ha nd-pollination. However, flowering may also be partly hormonally contr olled. In contrast, hand-pollinated plants exposed to high concentrati ons of heavy metals tended to have greater biomass of vegetative plant structures and higher number of flowers compared to nonpollinated pla nts. Together, these results suggest that environmental factors may al ter costs of reproduction but do not support the idea that these costs are more acute in resource (photosynthate)-limiting conditions.