Alteration of root hydraulic properties by rhizobial symbiosis

Resumen del póster presentado a la Saclay Plánt Sciences (SPS) Conference, celebrada en Evry (Francia) del 4 al 6 de julio de 2013.It is known that symbiosis with nitrogen fixing bacteria and legumes may enhance plant host tolerance to salinity. Most of the studies dealing with the interaction between legumes and nodule forming bacteria were focused to the effect of salt on the nitrogen fixation process. However how rhizobial symbiosis improves water status under salt stress conditions has been less studied. Here it was studied how inoculation of Phaseolus vulgaris plants with the rhizobial strain CIAT 899 modifies plant water relations under unstressed and salt stressed conditions. It was found that inoculated plants had higher leaf relative water content than non inoculated plants under NaCl conditions. Also, stomatal conductance was higher in inoculated than in non inoculated plants under both unstressed and salt stressed conditions. Thereafter, the capacity of absorbing water was estimated by calculating root hydraulic conductivity (L). While L was lower in inoculated plants than in non inoculated ones under unstressed conditions, salt treatrnent only inhibited L in non inoculated plants. These differences could not be explained by different root gene express ion of plasma membrane aquaporins (PIP). However, the PIP protein amount under saline conditions was higher in inoculated roots than in non inoculated ones. Moreover, roots of inoculated plants accumulate less Na+ ions than non inoculated ones under salt stress conditions. Therefore, rhizobial symbiosis ameliorate the water status of P. vulagris plants by dirninishing the changes caused by salt stress on water relation parameters like stomatal conductance and L and by inducing the accumulation of PIP proteins in their roots and decreasing the accumulation of Na+ ions in root tissues. Here is reported by the first time how rhizobial symbiosis may alter root hydraulic properties under any environmental conditions.Peer reviewe