Abstract
Photosynthetic gas exchange characteristics of two common boreal forest mosses, Sphagnum (section acutifolia) and Pleurozium schreberi, were measured continuously during the time required for the moss to dry out from full hydration. Similar patterns of change in CO2 assimilation with variation in water content occurred for both species. The maximum rates of CO2 assimilation for Sphagnum (approx. 7 μmol m−2 s−1) occurred at a water content of approximately 7 (fresh weight/dry weight) while for Pleurozium the maximum rate (approx. 2 μmol m−2 s−1) occurred at a water content of approximately 6 (fresh weight/dry weight). Above and below these water contents CO2 assimilation declined. In both species total conductance to water vapour (expressed as a percentage of the maximum rates) remained nearly constant at a water content above 9 (fresh weight/dry weight), but below this level declined in a strong linear manner. Short-term, “on-line” 13CO2 and C18O16O discrimination varied substantially with changes in moss water content and associated changes in the ratio of chloroplast CO2 to ambient CO2 partial pressure. At full hydration (maximum water content) both Sphagnum and Pleurozium had similar values of 13CO2 discrimination (approx. 15). Discrimination against 13CO2 increased continuously with reductions in water content to a maximum of 27 in Sphagnum and 22 in Pleurozium. In a similar manner C18C16O discrimination increased from approximately 30 at full hydration in both species to a maximum of 150 in Sphagnum and 90 in Pleurozium, at low water content. The observed changes in C18O16O were strongly correlated to predictions of a mechanistic model of discrimination processes. Field measurements of moss water content suggested that photosynthetic gas exchange by moss in the understory of a black spruce forest was regularly limited by low water content.
Similar content being viewed by others
References
Brooks A, Farquhar GD (1985) Effect of temperature on the CO2/O2 specificity of ribulose-1,5-bisphosphate carboxylase/oxygenase and the rate of respiration in the light: estimates from gas exchange experiments on spinach. Planta 165:397–406
Caemmerer S von, Evans J (1991) Determination of the average partial pressure of CO2 in chloroplasts from leaves of several C3 plants. Aust J Plant Physiol 18:287–305
Ciais P, Tans PP, Trollier M, White JC, Francey RJ (1995) A large northern hemisphere terrestrial CO2 sink indicated by the 13C/12C ratio of atmospheric CO2. Science 269:1098–1102
Cowan IR, Lange OL, Green TGA (1992) Carbon dioxide exchange in lichens: determination of transport and carboxylation characteristics. Planta 187:282–294
Craig H, Gordon LI (1965) Deuterium and oxygen-18 variations in the ocean and the marine atmosphere. In: Tongiorgi E (ed) Proceedings of a conference on stable isotopes in oceanograhic studies and palaeotemperatures, Spoleto, Italy. Lischi and Figli, Pisa, pp 9–130
Evans JR, Sharkey TD, Berry JA, Farquhar GD (1986) Carbon isotope discrimination measured concurrently with gas exchange to investigate CO2 diffusion in leaves of higher plants. Aust J Plant Physiol 13:281–292
Evans JR, Caemmerer S, Setchell BA, Hudson GS (1994) The relationship between CO2 transfer conductance and leaf anatomy in transgenic tobacco with a reduced content of Rubisco. Aust J Plant Physiol 21:475–495
Farquhar GD, Lloyd J (1993) Carbon and oxygen isotope effects in the exchange of carbon dioxide between terrestrial plants and the atmosphere. In: Ehleringer JR, Hall AE, Farquhar GD (eds) Stable isotopes and plant carbon-water relations. Academic Press, San Diego, pp 47–70
Farquhar GD, O'Leary MH, Berry JA (1982) On the relationship between carbon isotope discrimination and the intracellular carbon dioxide concentration in leaves. Aust J Plant Physiol 9:121–137
Farquhar GD, Ehleringer JR, Hubick KT (1989) Carbon isotope discrimination and photosynthesis. Annu Rev Plant Physiol Plant Mol Biol 40:503–537
Farquhar GD, Lloyd J, Taylor JA, Flanagan LB, Syversten JP, Hubick KT, Wong SC, Ehleringer JR (1993) Vegetation effects on the isotope composition of oxygen in atmospheric CO2. Nature 363:439–442
Flanagan LB (1993) Environmental and biological influences on the stable oxygen and hydrogen isotopic composition of leaf water. In: Ehleringer JR, Hall AE, Farquhar GD (eds) Stable isotopes and plant carbon-water relations. Academic Press, San Diego, pp 71–90
Flanagan LB, Varney GT (1995) Influence of vegetation and soil CO2 exchange on the concentration and stable oxygen isotope ratio of atmospheric CO2 within a Pinus resinosa canopy. Oecologia 101:37–44
Flanagan LB, Phillips SL, Ehleringer JR, Lloyd J, Farquhar GD (1994) Effect of changes in leaf water oxygen isotopic composition of the discrimination against C18O16O during photosynthetic gas exchange. Aust J Plant Physiol 21:221–234
Friedli H, Siegenthaler U (1988) Influence of N2O on isotope analyses in CO2 and mass-spectrometric determination of N2O in air samples. Tellus 40B:129–133
Guy RD, Fogel ML, Berry JA (1993) Photosynthetic fractionation of the stable isotopes of carbon and oxygen. Plant Physiol 101: 37–47
Lafleur PM, Schraeder CP (1994) Water loss from the floor of a subarctic forest. Arc Alp Res 26:162–158
Lloyd J, Syvertsen JP, Kriedemann PE, Farquhar GD (1992) Low conductance for CO2 diffusion from stomata to the sites of carboxylation in leaves of woody species. Plant Cell Environ 15:873–899
Murray KJ, Tenhunen JD, Nowak RS (1993) Photoinhibition as a control on photosynthesis and production of Sphagnum mosses. Oecoloiga 96:200–207
Oechel WC, Van Cleve K (1986) The role of bryophytes in nutrient cycling in the taiga. In: Van Cleve K, Chapin FS III, Flanagan PW, Viereck LA, Dyrness CT (eds) Forest ecosystems in the Alaskan taiga. (Ecological studies, vol 57) Springer, Berlin Heidelberg New York, pp 121–137
Price GD, Caemmerer S von, Evans JR, Yu J Lloyd J, Oja V, Kell P, Harrison K, Gallagher A, Badger M (1994) Specific reduction of chloroplast carbonic anhydrase activity by antisense RNA in transgenic tobacco plants has a minor effect on photosynthetic CO2 assimilation. Planta 193:331–340
Proctor MCF (1982) Physiological ecology: water relations, light and temperature responses, carbon balance. In: Smith AJE (ed) Bryophyte ecology. Chapman and Hall, London, pp 333–381
Proctor MCF, Raven JA, Rice SK (1992) Stable carbon isotope discrimination measurements in Sphagnum and other bryophytes: physiological and ecological implications. J Bryol 17: 193–202
Rice SK, Giles L (1996) The influence of water content and leaf anatomy on carbon isotope discrimination and photosynthesis in Sphagnum. Plant Cell Environ 19:118–124
Roeske CA, O'Leary MH (1984) Carbon isotope effects on the enzyme-catlayzed carboxylation of ribulose bisphosphate. Biochemistry 23:6275–6284
Rooney MA (1988) Short-term carbon isotope fractionation by plants. Ph. D. Thesis, University of Wisconsin
Sellers P, Hall F, Margolis H, Kelly B, Baldocchi D, Hartog G den, Cihlar J, Ryan MG, Goodison B, Crill P, Ranson KJ, Lettenmaier D, Wickland DE (1995) The Boreal Ecosystem-Atmosphere Study (BOREAS): a overview and early results from the 1994 field year. Bull Am Meteorol Soc 76:1549–1577
Silvola J (1990) Combined effects of varying water content and CO2 concentration on photosynthesis in Sphagnum fuscum. Holarct. Ecology 13:224–228
Skre O, Oechel WC (1981) Moss functioning in different taiga ecosystems in interior Alaska. I. Seasonal, phentoypic, and drought effects on photosynthesis and response patterns. Oecologia 48:50–59
Titus JE, Wagner DJ (1984) Carbon balance for two Sphagnum mosses: water balance resolves a physiological paradox. Ecology 65:1765–1774
White JWC, Ciais P, Figge RA, Kenny R, Markgraf (1994a) A high resolution record of atmospheric CO2 content from carbon isotopes in peat. Nature 367:153–156
White JWC, Figge RA, Markgraf V, Ciais P, Kenny R (1994b) Climate in the Pleistocene, reply. Nature 371:111–112
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Williams, T.G., Flanagan, L.B. Effect of changes in water content on photosynthesis, transpiration and discrimination against 13CO2 and C18O16O in Pleurozium and Sphagnum . Oecologia 108, 38–46 (1996). https://doi.org/10.1007/BF00333212
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00333212