Carbon isotope discrimination in leaf juice of Acacia mangium and its relationship to water-use efficiency

Abstract

Using the PMS pressure chamber and isotope mass spectrometer (MAT-252), the leaf juice of Acacia mangium was obtained, and the carbon isotope discrimination (D) representing the most recently fixed carbon in the juice was determined. At the same time, the water-use efficiency of A. mangium was estimated. The results indicated that the carbon isotope ratio in the air of forest canopy (d_a), 10 m high above ground averaged -7.57±1.41‰ in cloudy days, and -8.54±0.67‰ in sunny days, respectively. The diurnal change of the carbon isotope ratio in the photosynthetic products of the leaf juice (d_p) was of saddle type in cloudy days, but dropped down from morning to later afternoon in sunny days. A strong negative correlation between d_p and leaf-to-air vapor pressure deficit (D) was observed in sunny days, but a slight change in d_p was found in cloudy days. The d_p also decreased with decreasing leaf water potential (Ψ), reflecting that water stress could cause the decrease of d_p. The carbon isotope discrimination of the leaf juice was positively correlated with the ratio between intercellular (P_i) and atmospheric (P_a) partial pressure of CO₂. For A. mangium, the isotope effect on diffusion of atmospheric CO₂ via stomata was denoted by a = 4.6‰, and that in net C₃ diffusion with respect to P_i was indicated by b = 28.2‰. The results were in reasonable accord with the theoretically diffusive and biochemical fractionation of carbon isotope. It was defined that carbon isotope discrimination of photosynthetic products in A. mangium leaf juice was in proportion to that from photosynthetic products in dry material. The water-use efficiency estimated by the carbon isotope discrimination in leaf juice, fit well with that measured by gas exchange system (R² = 0.86, p< 0.0001). The application of leaf juice in measuring the stable carbon isotope discrimination would reduce the effects of fluctuating environmental factors during the synthesis of dry matter, and improve the eco-physiological studies on carbon and water balance when scaling from the plant to canopy in the fields.

Key words： carbon isotope discrimination; water-use efficiency; photosynthetic products in leaf juice

Acknowledgements

This study was supported by the National Natural Science Foundation of China (Grant No. 30428022, 30770328, 30871998) and Provincial Nature Science Foundation of Guangdong (No. 07006917).

References

1 Brugnoli E, Hubick K T, von Caemmerer S, Wong S C, Farquhar G D (1988). Correlation between the carbon isotope discrimination in leaf starch and sugars of C₃ plants and the ratio of intercellular and atmospheric partial pressured of carbon dioxide. Plant Physiol, 88: 1418–1424

2 Campbell G S, Norman J M (1998). An Introduction of Environmental Biophysics. New York: Springer-Verlag, 36–51

3 Comstock J, Ehleringer J (1993). Stomatal response to humidity in common bean (Phaseolus vulgaris). Implication for maximum transpiration rate, water-use efficiency and productivity. Aust J Plant Physiol, 20: 669–691

4 Craig H (1954). Carbon-13 variations in plants and the relationship between carbon-13 and carbon-14 variations in nature. J Geol, 62: 115–149

5 Ehleringer J R, Cooper T A (1986). Correlation between carbon isotope ratio and micro habitat in desert plants. Oecologia, 76: 562–566

6 Evans J R, Sharkey T D, Berry J A, Farquhar G D (1986). Carbon isotope discrimination measured concurrently with gas exchange to investigate CO₂ diffusion in leaves of higher plant. Aust J Plant Physiol, 10: 205–206

7 Farquhar G D, Ball M C, von Caemmerer S, Roksaadic Z (1982). Effects of salinity and humidity on δ¹³C value of halophytes-evidence for diffusional isotope fractionation determined by the ratio of intercellular/atmospheric partial pressure of CO₂ under different conditions. Oecologia, 52: 121–124

8 Farquhar G D, Ehleringer J R, Hubick C T (1989). Carbon isotope discrimination and photosynthesis. Ann Rev Plant Physiol, 40: 503–537

9 Farquhar G D, Richards R A (1984). Isotope composition of plant carbon correlates with water-use efficiency of wheat genoptype. Aust J Plant Physiol, 11: 539–552

10 Francey R T (1985). Cape Gm isotope measurements—a preliminary assessment. J Atmos Chem, 3: 247–260

11 Gessler A, Schrempp S, Matzarakisa A, Mayer H, Rennenberg H, Adams A (2001). Radiation modified effect of water availability on the carbon isotope composition of beech (Fagus sylvatica). New Phytol, 150: 653–664

12 Hubick K T, Shorter R, Farquhar G D (1988). Heritability and genotype environment interactions of carbon isotope discrimination and transpiration efficiency in peanut. Aust J Plant Physiol, 13: 803–816

13 Hubick K T, Farquhar G D (1989). Carbon isotope discrimination and the ratio of carbon obtained to water lost in barley cultivars. Plant, Cell Environ, 12: 795–804

14 Intergovernmental Panel on Climate Change (IPCC) (2007). Fourth assessment report of working group I. In:United Nation’s Environmental Program. Geneva, Switzerland

15 Keeling C D, Moor W M, Tans P P (1979). Recent trends in the ¹³C/¹²C ratio of atmospheric carbon dioxide. Nature, 277: 121–123

16 Martin B, Thorstenson Y R (1988). Stable carbon isotope composition (δ¹³C), water-use efficiency, and biomass productivity of Lycopersicon esculentuni, Lycopersicon pennellti, and the F1 hybrid. Plant Physiol, 88: 213–217

17 O’Leary M N (1981). Carbon isotope fractionation in plants. Phytochemistry, 20: 553–567

18 Park R, Epstein S (1960). Carbon isotope fractionation during photosynthesis. Geochim et Cosmochim Acta, 21: 110–126

19 Ponton S, Flanagan L, Alstad K, Johson B, Morgenstern K, Klgun N, Blackt A, Barr A (2006). Comparison of ecosystem water-use efficiency among Douglas-fir, aspen forest and grassland using eddy covariance and carbon isotope techniques. Global Change Biol, 12: 294–310

20 Qin D (2003). Fact, impact, adaptation and mitigation strategy of climate change. B Natl Nat Sci Found China, 7: 1–3

21 Vogel J C (1980). Fractionation of Carbon Isotope During Photosynthesis. Heidelberg: Springer-Verlag

22 Werner C, Unger S, Pereir J, Maia R, David T S, Kurz-Besson C, David J S, Máguas C (2006). Importance of short-term dynamics in carbon isotope ratio of ecosystem respiration (δ¹³CR) in Mediterranean oak woodland and linkage to environmental factors. New Phytol, 172: 330–346

23 Wright G C, Hubick K T, Farquhar G D (1988). Discrimination in carbon isotope of leaves correlated water-use efficiency of filed grown peanut cultivars. Austral J Plant Physiol, 15: 815–825

24 Yi X F, Zhuang X A (2005). Application of stable isotopic approach in ecology: a review. Chin J Ecol, 24(3): 306–314 (in Chinese)

25 Zheng X B, Zhuang Y, Gu G H (2005). Application of carbon isotope technique in forest ecosystem carbon cycling research. Chin J Ecol, 24(11): 1334–1338 (in Chinese)