SOME RESULTS PROVING THE SIGNIFICANCE OF THE CARBON ISOTOPE DISCRIMINATION BY THE PLANTS

Stela Cuna, Gabriela Balas

National Institute for Research and Development of  Isotopic and Molecular Technologies, Donath Str. 71-103, Cluj Napoca 400293, Romania

The carbon isotopic distribution of plants can  reveal informations about the physical, chemical, and metabolic processes involved in carbon transformations [1]. The paper reviews some results obtained on physical and enzymatic bases of carbon isotope discrimination during photosynthesis, noting how knowledge of discrimination can be used to provide additional insight into photosynthetic metabolism and environmental influences on that process. A variation of carbon isotope discrimination, as a result of a complex combination of variables such as precipitation, the CO2 concentration in atmosphere and the levels of pollutants, was found. Using the carbon isotope ratios of three flavor compounds, we have distinguished between natural products extracted from plants, and the same products obtained by chemical synthesis. As plant physiological processes interact with atmospheric trace gases, they leave a measurable isotopic “signature” [3], [4]. The composition of the atmosphere is strongly influenced by the terrestrial plants. For instance, photosynthesis and respiration have opposite effects on the isotope ratios: 13C/12C and 18O/16O in CO2. Plant photosynthesis and respiration modulate the atmospheric concentration of carbon dioxide, an important greenhouse gas, while plant transpiration influences climate through the transport of water from deep roots to the atmosphere. Measurements of the isotopic  composition of atmospheric trace gases provide integrated information about the net effects of biological processes on the atmosphere over different scales. It was shown that the isotopic composition of respiration, organic material, components of evapotranspiration and other trace gases improve our understanding of ecosystem processes, controlling biosphere-atmosphere exchange.

References
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