GASEOUS EXCHANGES AND THEIR REGULATION IN 2 SPECIES OF EVERGREEN OAK (QUERCUS ILEX AND QUERCUS SUBER)

This article presents a comparison on the physiology (hyrdic potential, stomatal resistances, transpiration, net photosynthesis) of young plants of Quercus ilex and Quercus suber submitted to different temperatures, light environment and water supply. Relative to temperature and light, the two species present similar reactions, although gaseous exchanges are more important on Quercus ilex. On the contrary, they present distinctive differences on water absorption. Quercus ilex have an important transpiration when water supply is not limited, but presents also a good tolerance to low hydric potentials and sufficient stomatal conductance according to photosynthetic production. On Quercus suber, survival seems more important than production : water consumption is relatively reduced at high water potential as good as at low water potential.