Infodoc : Sciences, Techniques et Culture

Plans of Quercus petraea, Pinus pinaster and Betula pendula were grown in three differnet substrates : SI, peat-sand mix (1: 2, v/v); SII, peat-sand mix (2: 1, v/v); and SIII peat-clay mix (1: 3, v/v) and submitted to drought stress. Large differences in growth and water relations were recorded among the three species. Under well-watered conditions, birch displayed higher values of stomatal conductance, of whole plant transpiration flux density, and of specific soil-to-leaf hydraulic conductivity than oak and pine. During stress, birch consumed all available water very quickly, but still displayed higher predawn leaf water potential than the 2 other species. Intense stomatal closure was recoded at higher values of predawn leaf water potential (close to -1.2 MPa) than in the two other [...]

Plans of Quercus petraea, Pinus pinaster and Betula pendula were grown in three differnet substrates : SI, peat-sand mix (1: 2, v/v); SII, peat-sand mix (2: 1, v/v); and SIII peat-clay mix (1: 3, v/v) and submitted to drought stress. Large differences in growth and water relations were recorded among the three species. Under well-watered conditions, birch displayed higher values of stomatal conductance, of whole plant transpiration flux density, and of specific soil-to-leaf hydraulic conductivity than oak and pine. During stress, birch consumed all available water very quickly, but still displayed higher predawn leaf water potential than the 2 other species. Intense stomatal closure was recoded at higher values of predawn leaf water potential (close to -1.2 MPa) than in the two other species. At higher stress intensities, birch reduced drastically its transpiring area by leaf shedding. The clayey substrate (SIII) limited severely the growth of oaks, and
pines, but not of birches, without any apparent deficiency as evidenced by the mineral composition of the leaves. Water relations and stomatal conductance remained almost unaffected by substrate composition in the three species. With increasing water stress, the only difference observed among substrates was the time course of soil water depletion, due to differences in leaf area. Stomatal conductance and soil-to-leaf specific hydraulic conductance were well correlated in all species, but important interspecific differences occured; birches diffeed significantly from the two other species. "(Résumé des auteurs)".