Morphological and physiological modifications of Cistus salvifolius L. winter leaves in response to the rise of winter temperatures

The global climate is predicted to change in the next century; for the Mediterranean Basin an increase in air temperature more than 4°C and a higher frequency of extreme climatic events suchas drought and heat waves are expected. In this work the response of Cistus salvifolius L. to the rise of winter temperature has been studied. Plant acclimated to winter conditions (outdoor) were moved into a greenhouse (indoor) at higher temperature and eco-physiological behaviour was analyzed onleaves after 15 days from plant transferring (IND15d) and on leaves developed indoor (IND). IND leaves were characterized by reduced thickness, higher specific leaf area (SLA), higher CO2 mesophyll conductance and photosynthetic rate, and lower respiratory rate than leaves grown outdoor (OUT) upon current winter conditions. In IND15d leaves no improvement of photochemical activity was found. When IND leaves were subjected to rapid increase of air temperature the CO2 fixation was not limited indicating an high thermotolerance of photosynthetic machinery. The results for IND leaves indicate the occurrence of a strategy that merging changes in leaf structure as well as in photosynthetic regulation allows C. salvifolius to maintain an elevated carbon gain in response to temperature increase.