K. Saikkonen et al., INTERACTIVE EFFECTS OF POLLINATION AND HEAVY-METALS ON RESOURCE-ALLOCATION IN POTENTILLA-ANSERINA L, Ecology, 79(5), 1998, pp. 1620-1629
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.