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

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In situ measurement of leaf water use efficiency of lilac (Syringa vulgaris): comparison with crop plants O. Bethenod, J. Pilarski* P. Quetin INRA, 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 MPa In order to understand the regulation be- for potato and -1.6 MPa for maize and tween the net COg assimilation rate (A) lilac at Grignon. In this case, C remains i and the transpiration rate (E), leaf gas constant throughout the day (Bethenod et measured in the field; leaf exchange al., 1988). was efficiency (WUE) of lilac (Syrin- water use (1973) proposed to represent this Jones ga vulgaris) was compared to those of regulation by the curve of A versus C i maize (Zea mays L.) and potato (Sola- called the demand function (Farquahar tuberosum L.). and Sharkey, 1982). If C is placed on the a num 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 a out 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. Our depends upon the intercellular CO 2 first aim was to study the proportionality concentration (C and stomatal conduc- ) i between A and g in order to show how , c tance (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 on C 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 maximal tween A and g,. All 3 species considered value (A The second aim of this work ). max here are able to maintain their xylem was to compare the A values for the max water potential: regardless of the value studied species. Present * address: Polish Academy of Sciences, Laboiratory of Photosynthesis, St Jana 22, 31-018 Cracow, aboratory Poland.
Materials and Methods Results grown in the field Lilac, 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 (PPFD) in Fig. 2. Note that the lilac data leaf chamber (A.D.C.). The gas circuit was show a low scatter. For potato, the high modified: pressurized dry air from cylinders pro- scatter could indicate water stress; but this vided a C0 concentration in the chamber 2 is not apparent from leaf water potential higher than that in natural air. Two gas-flow controllers (Tylan) ensured a constant flow rate data (Bethenod et al., 1988). This scatter at both reference and chamber levels. can be induced by: 1) individual variability C0 net assimilation (A) data were normal- 2 2) changes in A between morning and and ized at 338 jlmol for C according to 1 mol- ’ , a evening at the same level of incident Bethenod et al. (1988) for C leaves; for C 4 3 PPFD. The maximum values for potato leaves, A is approximately the same above 320 about the same as those for lilac. jlmol C0 Fig. 1 shows 3 hypothetical 1 mol- . ’2 are adjustments between demand and supply func- increases slightly when PPFD de- i C tions. The data shown in following figures cor- below 500 ymol-m- (Fig. 3). 1 -s- 2 respond to a typical day for each species. Each creases symbol represents a leaf on different plants in 4 g,. Up to Fig. disp:lays ,4! versus the field for maize and potato, and of 2 trees in values between 0.20 and 0.23 a hedge for lilac. g!
scribed (Schulze by hyperbolic , 1 s 2 m- ’ mol the g dependence of A is c a curve c and Hall, 1982; Kuppers. 1984), which almost linear and the slope of this line may be reduced to both asymptotes (Per- represents C Beyond these values, . i -C a eira et al., 1987). The regulated phase A does not increase for both C plants, 3 and the maximum assimilation phase although g can be large for lilac. Conse- . could be summarized by these 2 asymp- quently, 2 phases exist in this A - g rela- c totes (Fig. 5). H is the point where the tionship: a C regulated phase for g! below i maximum of demand function crosses the 0.2 mol and a maximum assimila- , 1 s 2 m- ’ C;regulation line. We can observe that, if tion phase for g above 0.23 mol!m-2!s-!. c WUE of maize is higher than the WUE of lilac or potato, the junction occurs within the same range of values of g e e2 (0.2::=;;g mol.m- for the 3 plants ) 1 s- ’
European hedgerow. II. Stomatal response, References water use, and hydraulic conductivity in the root/leaf pathway. Oecologia (Berlin) 64, 344- Bethenod 0., Katerji N., Quetin P. & Bertolini 354 J.M. (1988) Efficience de I’eau d’une culture de Pereira J.S., Tenhunen J.D. & Lange O.L. pomme de terre (Solanum tuberosum L. cv. (1987) Stomatal control of photosynthesis of Bintje) 1. Mise en evidence de la r6gulation du Eucalyptus globulus Labill. Trees under field C0 interneA I’dchelle foliaire. Photosynthetica 2 conditions in Portugal. J. Exp. Bot. 195, 1678- 22,491-501 1688 Bierhuizen J.F. & Slatyer R.O. (1965) Effect of atmospheric concentration of water vapor and Schulze E.D. & Hall A.E. (1982) Stomatal C0 in determining transpiration--photosynthe- 2 responses, water loss and C0 assimilation 2 sis relationship of cotton leaves. Agric. Meteo- rates of plants in contrasting environments. rol. 2, 259-270 In: Physiological Plant Ecology II: Water Relations and Carbon Assimilation. (Lange et Farquhar G.D. & Sharkey T.D. (1982) Stomatal aL, eds.) Encyclopedia of Plant Physiology conductance and photosynthesis. Annu. Rev. New series, vol. 12B, Springer-Verlag, Berlin, Plant Physiol. 33, 317-345 pp. 181-230 Jones H.G. (1973) Limiting factors in photosyn- thesis. New Phytol. 72, 1089-1094 Wong S.C., Cowan LR. & Farqubar G.D. (1979) Kuppers M. (1984) Carbon relations and com- Stomatal conductance correlates with photo- petition between woody species in a Central synthetic capacity. Nature 282, 424-426