Inter-comparisons in the gas exchange patterns and root characteristics under both well-watered and drought conditions were done in three-years-old seedlings of three oak species (Quercus cerris L., Q. frainetto Ten., and Q. ilex L.) growing in controlled environment. Well-watered Q. cerris had greater physiological performances than other oaks, but under drought it was not able to face the water stress showing also structural modifications such as reduction of root length and average diameter. On the other hand, Q. ilex maintained root growth both in drought or well-watered soils. Moreover, it was able to keep open stomata also under water stress, although stomatal conductance (gs) was low. Q. frainetto had an intermediate position in regard to its physiological and root structural characteristics between Q. cerris and Q. ilex under drought stress. For all oaks the relationship between gs and the ratio of sub-stomatal and ambient CO2 concentration (Ci/Ca) highlighted the dynamic adaptation of gs to the increase of hydraulic resistances of leaf, stem, and roots portions, more evident during the air humidity change and progressive soil dehydration. This suggests a well-triggered above-and under-ground mechanism to endure the drought stress. and F. Manes ... [et al.].
In the frame of the foreseen climate global changes we analysed the physiological responses of Arbutus unedo L. to the variations of carbon dioxide concentration, leaf temperature, and irradiance by measurements of leaf gas exchange and leaf water potential performed both in field and in the laboratory. Stomatal conductance was not affected by increase of leaf temperature. The growth conditions of potted plants likely made stomata more sensitive to the variation of external parameters than naturally growing plants. The interaction between high CO2 concentration and temperature involved important down-regulation mechanisms in the metabolic pathway of the carbon fixation. From an ecological point of view, the ability of A. unedo to adapt to the field stress makes it highly competitive in the Mediterranean plant community. and M. Vitale, F. Manes.