Consequences of ramets helping ramets: No damage and increased nutrient use efficiency in nurse ramets of Glechoma longituba

Source–sink relationships determine the transfer of resources among interconnected ramets of clonal plants and these relationships depend on resource regimes experienced by ramets. We hypothesized that if ramets growing in nutrient-richer patches support ramets in nutrient-poorer patches, then this support would weaken the performance of supporters themselves. This hypothesis was tested in an experiment, in which two interconnected ramet-groups of Glechoma longituba were subjected to four levels of nutrient-patch contrast. For nurse ramets, midday leaf water potential, net photosynthetic rate, fluorescence yield, specific root length, biomass, and root weight ratio remained unchanged along the gradient of patch contrast, indicating that no damage occurs to these ramets. Nitrogen use efficiency and phosphorus use efficiency of nurse ramets significantly increased with increasing patch contrast, suggesting that these increases may allow nurse ramets from habitats higher in patch contrast to have a greater capacity for export of nutrients than those ramets from habitats lower in patch contrast. In addition, we discuss the likely implications of these findings.