Hydrogen isotope discrimination in higher plants: Correlations with photosynthetic pathway and environment
✍ Scribed by H. Ziegler; C. B. Osmond; W. Stichler; P. Trimborn
- Book ID
- 104756069
- Publisher
- Springer-Verlag
- Year
- 1976
- Tongue
- English
- Weight
- 713 KB
- Volume
- 128
- Category
- Article
- ISSN
- 0032-0935
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✦ Synopsis
The ratio of deuterium to hydrogen (expressed as 6D) in hydrogen released as water during the combustion of dried plant material was examined. The 6D value (metabolic hydrogen) determined on plant materials grown under controlled conditions is correlated with pathways of photosynthetic carbon metabolism. C3 plants show mean 5D values of -132O/oo for shoots and -117O/oo for roots; C4 plants show mean 6D values of -91~ for shoots and -77~
for roots and CAM plants a 6D value of -75~
for roots and shoots. The difference between the 5D value of shoot material from C3 and C4 plants was confirmed in species growing under a range of glasshouse conditions. This difference in 6D value between C3 and C4 species does not appear to be due to differences in the 6D value (tissue water) in the plants as a result of physical fractionation of hydrogen isotopes during transpiration. In C3 and C4 plants the hydrogen isotope discrimination is in the same direction as the carbon isotope discrimination and factors contributing to the difference in 5D values are discussed. In CAM plants grown in the laboratory or collected from the field 6D values range from -75O/0o to +50O/oo and are correlated with ~3C values. When deprived of water, the 6D value (metabolic hydrogen) in both soluble and insoluble material in leaves of Kalanchoe daigremontiana Hamet et Perr., becomes less negative. These changes may reflect the deuterium enrichment of tissue water during transpiration, or in field conditions, may reflect the different 6D value of available water in areas of increasing aridity. Whatever the origin of the variable 5D value in CAM plants, this parameter may be a useful index of the water relations of these plants under natural conditions.