Phenotypic plasticity of different Quercus suber L. provenances under water stress conditions
Abstract: In the overall context of global warming and of Mediterranean forests fragility, the
success of new afforestation of cork oak (Quercus suber L.) requires the selection at an early
stage of growth of provenances adapted to low water availability. Differences in tolerance to
water shortage were tested among seedlings of Quercus suber L. from three Tunisian
provenances [El Feija (EF), Ben Metir (BM), and Oued Zen (OZ)]. Different provenances were subjected to th e following water regimes:1) irrigation at 100 % of the field capacity (FC); 2) 50 % of FC;3) 25 % of FC The tolerance to different water regimes was assessed by measuring micromorphological (i.e., leaf area, trichome and stomatal density and size), and physiological (i. e., gas exchange and chlorophyll concentration) variables. Phenotypic plasticity (PI) and Water Use Efficiency (WUE) indices were also calculated. Our results indicate that seedlings subjected to water stress were characterized by a decreasing leaf area and an increasing trichome and stomatal density, as well as a reduction in stomatal conductance, photosynthesis and chlorophyll pigment contents, 90 days after the beginning of experimental trials. The effect of water stress on plant physiology was related to both water regimes applied the Q. suber provenances. Seedlings from EF and BM showed a higher PP than plants from OZ. The better flexibility towards water stress was reflected in the EF plants by an increase of the intrinsic water use efficiency (WUEint). Selecting the most water-stress adapted provenances could contribute to the success of new afforestation where water resources are deficient.