Biosynthetic and environmental effects on the stable carbon isotopic compositions of anteiso- (3-methyl) and iso- (2-methyl) alkanes in tobacco leaves
2008
Grice, Kliti | Lu, Hong | Zhou, Youping | Stuart-Williams, Hilary | Farquhar, Graham D.
Nicotiana tabacum is the only plant known to synthesise large quantities of anteiso- (3-methyl) alkanes and iso- (2-methyl) alkanes. We investigated the carbon isotope ratios of individual long-chain n-alkanes, anteiso- and iso-alkanes (in the C29-C33 carbon number range) extracted from tobacco grown in chambers under controlled conditions to confirm the pathway used by the tobacco plant to synthesise these particular lipids and to examine whether environmental data are recorded in these compounds. Tobacco was grown under differing temperatures, water availabilities and light intensities in order to control its stable carbon isotope ratios and evaluate isotopic fractionations associated with the synthesis of these particular lipids. The anteiso-alkanes were found to have a predominant even-carbon number distribution (maximising at C32), whereas the iso-alkanes exhibit an odd-carbon number distribution (maximising at C31). Iso-alkanes were relatively more abundant than the anteiso-alkanes and only two anteiso-alkanes (C30 and C32) were observed.
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