Hormonal modification of resource sharing in the clonal plant Fragaria chiloensis

1. Clonal plants can share resources such as carbon and nitrogen among connected, separately rooted plant units or ramets. In many cases. resource sharing tends to equalize the performance of ramets, suggesting that differences in resource supply drive the sharing process, with resources moving from ramets with high access to resources to those with low access to resources. However, some patterns of apparent C and N sharing in the stoloniferous wild strawberry Fragaria chiloensis make the growth of ramets less equal, which is inconsistent with this model of resource sharing. As hormones are a mechanism by which non-clonal plants can make the growth of the branches of a shoot less equal, we hypothesized that clonal plants might use hormones to modify patterns of resource sharing between ramets. 2. Auxin (IAA) or cytokinin (BA) was applied to the shoot tip of ramets using a non-invasive protocol previously shown to increase internal hormone concentrations. C-14 or N-15 was then fed to connected ramets, and the amounts of C-14 or N-15 imported by the hormone-treated ramets and by suitable controls were measured. 3. Ramets treated with IAA showed greater C import from connected ramets than did control ramets when the IAA-treated and control ramets were shaded and the connected ramets were not. Ramets treated with IAA showed increased N import from connected ramets compared with the controls when the IAA-treated and control ramets were given less N than the connected ramets, and were also younger than the connected ramets. IAA had no consistent effect on C or N sharing between ramets given the same resource treatments as one another and did not affect the direction of N sharing, which is strongly acropetal in F chiloensis. BA showed little effect on resource sharing. 4. The results supported the hypothesis that hormones can modify patterns of resource sharing between ramets in clonal plants. In F chiloensis, auxin can enhance resource import by ramets in relatively resource-poor microsites. Clonal plants may use hormones as a mechanism for physiological integration of connected ramets.