Hydrogen-isotope composition of leaf water in C3and C4plants: its relationship to the hydrogen-isotope composition of dry matter
✍ Scribed by F. W. Leaney; C. B. Osmond; G. B. Allison; H. Ziegler
- Publisher
- Springer-Verlag
- Year
- 1985
- Tongue
- English
- Weight
- 604 KB
- Volume
- 164
- Category
- Article
- ISSN
- 0032-0935
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✦ Synopsis
The natural abundance hydrogen-isotope composition of leaf water (5~ 2~ and leaf organic matter (5~rg) was measured in leaves of C a and C 4 dicotyledons and monocotyledons. The 6~20 value of leaf water showed a marked diurnal variation, greatest enrichment being observed about midday. However, this variation was greater in the more slowly transpiring C 4 plants than in C 3 plants under comparable environmental conditions. A model based on analogies with a constant feed pan of evaporating water was developed and the difference between C 3 and C4 plants expressed in terms of either differences in kinetic enrichment or different leaf morphology. Microclimatic and morphological features of the leaves which may be associated with this factor are discussed. There was no daily excursion in lhe u, Dp~~ value in leaves of either C 3 or C4 plants. When 3~rg values were referenced to the mean 6o n~~ values during the period of active photosynthesis, the discrimination against deuterium during photosynthetic metabolism (A D) was greater in C 3 plants (-117 to -121% o) than in C~ plants (-86 to -109~
These results show that the different water use "strategies" of C 3 and C 4 plants are responsible for the measured difference in deuterium-isotope composition of leaf water. However, it is unlikely that these physical processes account fully for the differences in hydrogen-isotope composition of the products of C 3 and C 4 photosynthetic metabolism.