TAILIEUCHUNG - Báo cáo lâm nghiệp: "In situ measurement of leaf water use efficiency of lilac (Syringa vulgaris): comparison with crop plants"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: In situ measurement of leaf water use efficiency of lilac (Syringa vulgaris): comparison with crop plants. | 421s Ann. Sci. For. 1989 46 suppl. 421s-425s Forest Tree Physiology E. Dreyer etal. eds. Elsevier INRA In situ measurement of leaf water use efficiency of lilac Syringa vulgaris comparison with crop plants o. Bethenod J. Pilarski and p. Quetin INRA Station de Bioclimatologie 78850 Thiverval-Grignon France Introduction In order to understand the regulation between the net co2 assimilation rate A and the transpiration rate E leaf gas exchange was measured in the field leaf water use efficiency WUE of lilac Syrings vulgaris was compared to those of maize Zea mays L and potato Sola-num tuberosum L . Bierhuizen and Slatyer 1965 pointed out that for a given water saturation deficit vpd WUE A E at the leaf level depends upon the intercellular co2 concentration Cj and stomatai conductance gc A gc Ca-Cị E gc vpd A E Ca - Cj vdp with ca co2 concentration in air. A direct estimate of WUE is therefore given by the slope of the relationship between A and gc. All 3 species considered here are able to maintain their xylem water potential regardless of the value their predawn water potential reached between and MPa the minimal xylem water potential did not fall below MPa for potato and MPa for maize and lilac at Grignon. In this case Cj remains constant throughout the day Bethenod et al. 1988 . Jones 1973 proposed to represent this regulation by the curve of A versus c ị called the demand function Farquahar and Sharkey 1982 . If ca is placed on the Cj axis the leaf co2 conductance gc is the slope of the straight line joining ca to the corresponding Cj on the demand function this defines the supply function. Our first aim was to study the proportionality between A and gc in order to show how demand function and supply function adjust to each other. But beyond a limit on the demand function Cj increases and WUE decreases because of large gc values A then remains at its maximal value Amax . The second aim of this work was to compare the Amax values for the .

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