Presence of developing ramets of Fragaria vesca L. increases photochemical efficiency in parent ramets

Clonal plants may translocate photosynthates, water, and nutrients from established ( source) ramets to developing ( sink) ramets. The sink/source hypothesis states that photosynthesis may be regulated, at least in part, by the balance between source and sink tissues. We investigated the influence of physiological integration on photosynthetic efficiencies to test predictions based on the sink/source hypothesis that photosynthetic efficiencies in parent ramets may be increased by the assimilate demand made by connected offspring ramets. We grew parent ramets of Fragaria vesca connected to four, one, or no offspring ramets. They were grown in well-watered or drought-stress conditions. All parent ramets survived at the end of the experiment, regardless of the number of offspring ramets they supported or the moisture conditions in which these were growing. However, the survivorship of offspring ramets was higher for well-watered and connected ramets than for drought-stressed and disconnected ramets. In parent ramets, spectral and fluorescence parameters related to photochemical efficiency increased with the number of interramet connections. We conclude that developing ramets of F. vesca, by acting as sinks for assimilates, induce an enhancement of the photosynthetic activity of the parental ramets by a feedback regulation process.