Abstract: The effect of water shortage and nitrogen deficiency on physiology behaviour hasbeen studied in cork oak (Quercus suber L.). Two years old seedlings have been submitted todifferent water and nitrogen treatments. Two water-nitrogen regimes were adopted (W: wellwatered plant, S: water-stressed plant, N1: plant receiving 3g of nitrogen, N0: plant withoutnitrogen) corresponding to the four following combinations: WN1, WN0, SN1, SN0. We assessedmorphological parameters (seedlings size, leaves number and diameter of the collar) andphysiological parameters (stomata conductance (g), photosynthesis (A) and chlorophyll content).Morphological parameters did not show a significant difference between the different treatments.Low stomata conductance and photosynthesis level were closely related to water-stressedseedlings compared to well watered ones. The average of water use efficiency (A/g) increased by25% in water-stressed seedlings. Chlorophyll content, assessed with CCM-200 chlorophyllcontent meter, decreased in seedlings deprived from nitrogen treatment. Further ecophysiologicalstudies are in progress including assessment of the effect of increasing CO2 on water useefficiency through A/Ci curves.