Physiological integration of connected balsam poplar ramets.
Kokouvi Adonsou, Annie DesRochers, Francine Tremblay.
Clonal integration between ramets can be an ecological advantage of clonal plant species in environments where resources are
patchily distributed. We investigated physiological integration among Populus balsamifera L. ramets under drought stress in
order to demonstrate water sharing between connected ramets. Pairs of connected ramets were grown in separate pots in the
greenhouse where half of ramets had the parental root connection severed and half were left intact. Drought stress was applied
to one ramet, and growth, specific leaf area (SLA), net photosynthesis, stomatal conductance, leaf water potential and carbon
isotopic composition (?13C) were measured after an 8-week growing period. Droughted ramets connected to watered ramets
were able to maintain high gas exchange activity and water potential, similar to watered ramets. Leaf water potential and SLA
results showed that the root connection was more beneficial for proximal compared with distal ramets. The parental root connection
also allowed droughted ramets to discriminate more against 13C compared with severed ramets. In conclusion, this study
shows compelling evidence of physiological integration of connected P. balsamifera ramets through water sharing.