Mediterranean tomato landraces adapted to arid environments represent an option to counteract drought, and to address the complexity of responses to water deficit and recovery, which is a crucial component of plant adaptation mechanisms. We investigated physiological, biochemical and molecular responses of two Mediterranean tomato landraces, "Locale di Salina" (Lc) and "Pizzutello di Sciacca" (Pz) under two dehydration periods and intermediate rehydration in greenhouse pot-experiments. Relationship between CO2 assimilation and stomatal conductance under severe water stress (gs < 0.05 mol m-2 s-1 ) indicated the occurrence of stomatal and non-stomatal limitations of photosynthesis. Gas-exchanges promptly recovered within 2-3-day re-hydration. ABA and gs showed a strict exponential relationship. Both leaf ABA and proline peaked under severe water stress. Lc showed higher accumulation of ABA and higher induction of the expression of both NCED and P5CS genes than Pz. PARP increased during imposition of stress, mainly in Lc, and decreased under severe water stress. The two landraces hardly differed in their physiological performance. Under severe water stress, stomatal conductance showed low sensitivity to ABA, which instead controlled stomatal closure under moderate water stress (gs > 0.15 mol m-2 s-1 ). The prompt recovery after re-dehydration of both landraces confirmed their drought tolerant behaviour. Differences between the two landraces were instead observed at biochemical and molecular levels. This article is protected by copyright. All rights reserved.
