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

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Báo cáo lâm nghiệp: "In situ measurement of leaf water use efficiency of lilac (Syringa vulgaris): comparison with crop plants"In situ measurement of leaf water use efficiencyof lilac (Syringa vulgaris): comparison with crop plantsO. Bethenod, J. Pilarski* P. QuetinINRA, Station de Bioclimatologie, Thiverval-Grignon, France 78850 predawn water potential reached be-Introduction their tween 0.2 and 0.6 MPa, the minimal xylem water potential did not fall below -1.3 MPaIn order to understand the regulation be- for potato and -1.6 MPa for maize andtween the net COg assimilation rate (A) lilac at Grignon. In this case, C remains iand the transpiration rate (E), leaf gas constant throughout the day (Bethenod et measured in the field; leafexchange al., 1988). was efficiency (WUE) of lilac (Syrin-water use (1973) proposed to represent this Jonesga vulgaris) was compared to those of regulation by the curve of A versus C imaize (Zea mays L.) and potato (Sola- called the demand function (Farquahar tuberosum L.). and Sharkey, 1982). If C is placed on the anum C axis, the leaf C0 conductance (g is 2 i ) c Bierhuizen and Slatyer (1965) pointed the slope of the straight line joining C to aout that, for a given water saturation deficit the corresponding C on the demand func- i(vpd), WUE (AlE), at the leaf level tion: this defines the supply function. Ourdepends upon the intercellular CO 2 first aim was to study the proportionalityconcentration (C and stomatal conduc- ) i between A and g in order to show how , ctance (g A= C E= 1.6 9c ): a cc - (g Ci); demand function and supply function(vpd); AlE=(C C vdp; with - )/1.6 ai adjust to each other. But beyond a limit onC C0 concentration in air.a2 = the demand function, C increases and i A direct estimate of WUE is therefore WUE decreases because of large g c the slope of the relationship be-given by values; A then remains at its maximaltween A and g,. All 3 species considered value (A The second aim of this work ). maxhere are able to maintain their xylem was to compare the A values for the maxwater potential: regardless of the value studied species.Present* address: Polish Academy of Sciences, Laboiratory of Photosynthesis, St Jana 22, 31-018 Cracow, aboratoryPoland.Materials and Methods Results grown in the fieldLilac, potato and maize Normalized net assimilation (/!) is plotted were Grignon, 40 km west of Paris.at photosynthetic photon flux density versus Measurements were made with a Parkinson ...