Effect of water and salt stress on energy partitioning of two grapevine rootstock genotypes: a quantitative assessment

The ability of plants to adapt and/or acclimate to different environments is related to the plasticity and resilience of photosynthesis. This study aims at assessing the effects of salinity, drought and recovery on photosynthesis being either direct (stomatal limitations) or secondary (oxidative stress). Combined measurements of gas exchange and chlorophyll fluorescence enabled to quantify the absorbed energy used for net photosynthesis and that dissipated by photoprotective mechanisms. Measurements were performed under controlled conditions on leaves of susceptible (101.14) and new putative tolerant selection (M4) grapevine rootstocks in control and progressive drought and salt loading conditions. Leaves of 101.14 showed higher photosynthetic performances than the M4 in well-watered conditions. However, M4 showed a greater ability to tolerate increasing salt concentration and drought and an almost complete recovery after re-watering. Quenching analysis revealed the photoprotective thermal dissipation (Phi NPQ) as the major responsible for the different stress responses among susceptible and tolerant rootstock studied.