On the Relationship Between Carbon Isotope Discrimination and the Intercellular Carbon Dioxide Concentration in Leaves

Abstract

Theory is developed to explain the carbon isotopic composition of plants. It is shown how diffusion of gaseous COz can significantly affect carbon isotopic discrimination. The effects on discrimination by diffusion and carboxylation are integrated, yielding a simple relationship between discrimination and the ratio of the intercellular and atmospheric partial pressures of COZ. The effects of dark respiration and photorespiration are also considered, and it is suggested that they have relatively little effect on discrimination other than cia their effects on intercellular p(COz). It is also suggested that various environmental factors such as light, temperature, salinity and drought will also have effects via changes in intercellular p(C0,). A simple method is suggested for assessing water use efficiencies in the field.

The effects of salinity, crassulacean acid metabolism and plant age on the carbon isotope composition of Mesembryanthemum crystallinum L., a halophytic C3-CAM species

“…Independent of such stress-induced alterations of the proportion of CO 2 assimilated during the dark and light, d 13 C value can also be affected by stress-related effects on the diffusional limitation of CO 2 uptake. Increased diffusional limitation of C 3 photosynthetic CO 2 uptake in the light can lead to less negative d 13 C values whereas more negative d 13 C values are to be expected if CO 2 uptake in the dark becomes increasingly diffusion-limited (Farquhar et al 1982b(Farquhar et al , 1989.…”

Water acquisition patterns of two wet tropical canopy tree species of French Guiana as inferred from H218O extraction profiles

“…where R sample and R smow are the 18 O/ 16 O ratio in the water sample and in the conventional standard (SMOW), respectively.…”

“…This methodology is based on the fact that (1) soil water extraction by roots does not induce isotopic fractionation of either oxygen or hydrogen isotopes of water [2,44,45] and (2) gradients in oxygen or hydrogen isotope composition (δ 18 O or δ 2 H) of soil water with soil depth may arise from seasonal variations in rainfall isotope signature [11,12] and from the isotope fractionation that occurs during surface soil water evaporation (see review in [16]). Therefore, by comparing instantaneous δ 18 O or δ 2 H of xylem sap water with that of soil water, it is possible to interpolate a mean soil depth where roots extract water.…”

Ecophysiological responses of plants to global environmental change since the Last Glacial Maximum

“…are the ambient and intercellular partial pressures of CQ2 respectively (Farquhar, O'Leary & Berry, 1982). Equation (1) shows that when stomatal conductance is small, relative to the leaf capacity to fix COg, then pf is small and A ^'C tends towards 4-4%^.…”