Seasonal variation of fig tree (Ficus carica L.)physiological characteristics reveals its adaptation performance.

In the context of climate change, understanding fig trees physiology is very important, since the areas of fig production registered a large climate variability that severely affects fruit quality. The present study was conducted to evaluate the seasonal changes of physiological leaf behaviour of two Tunisian fig cultivars, Zidi and Bither Abiadh during two years. Plants were subjected to full irrigation to maintain the soil moisture around pot capacity through the experimental period. Leaf gas exchange characteristics (net photosynthetic rate (PN), stomatal conductance (gs), and transpiration rate (E)), chlorophyll content index, leaf temperature and the maximum photochemical efficiency of PSII (Fv/Fm)were measured. Results showed that the photosynthetic characteristics changed during the growing season. Changes of photosynthetic CO2 assimilation, stomatal conductance, and chlorophyll content were not significantly affected by cultivar, and their variation was attributed to year. Seasonal changes of PN and gs were similar suggesting that both processes are dependent. Indeed the best photosynthetic performance of fig occurred about 80-87 days after bud break (spring)of the second season of growth, being supported by a high stomatal aperture. The lowest values of PN, E and gs were recorded 156 days after bud break (summer)for 2017. The decrease of gas exchange rates and high temperatures were registered during the same dates. A little increase of the photosynthetic characteristics and chlorophyll content was noticed in the autumn period, about 180 days after bud break, until a definitive decrease at the end of the growing season with the occurrence of low winter temperature. These results revealed particular adaptive behaviour and could be used as preliminary criteria to predict the future impact of environmental abiotic stresses on ecophysiological fig tree behaviour.