Low CO2 does not remove diffusional limitation to photosynthesis in salt stressed tomato during osmotic phase

Salinity is one of the main environmental stress for crops such as tomato which is widely spread in the Mediterranean region. It is now widely considered that in plant adaptation to salts, the time scale of the response is essential. During the initial phase of response to salinity, when the osmotic effect predominates, plant response to salts is regulated by hormones, and between them abscisic acid plays a crucial role. We showed that on tomato crops during the first phase (osmotic one) low CO2 conditioning treatment before photosynthetic response to carbon dioxide concentration (A-Ci curve) is not applicable because diffusional limitations to photosynthesis is not removed by low CO2 air concentration. Conditioning at low CO2 is not sufficient to remove diffusional limitation of photosynthesis in salt stressed tomatoes during osmotic phase.