Hydrogen, carbon and nitrogen isotopic fractionations during chlorophyll biosynthesis in C3 higher plants

We determined hydrogen, carbon and nitrogen isotopic compositions of chlorophylls a and b isolated from leaves of five C3 higher plant species (Benthantidiajaponica, Primitsjaponica, Acer carpinifolium, Acer argutum and Querus mongloica), and hydrogen and carbon isotopic compositions of phytol and chlorophyllides in the chlorophylls to understand isotopic fractionations associated with chlorophyll biosynthesis in these species. Chlorophylls are depleted in D relative to ambient water by similar to 189 parts per thousand and enriched in C-13 relative to bulk tissue by similar to 1.6 parts per thousand. These data can be explained by the contribution of isotopic fractionations during phytol and chlorophyllide biosyntheses. Phytol is more depleted in both D (by similar to 308 parts per thousand) and C-13 (by similar to 4.3 parts per thousand), while chlorophyllides are less depleted in D (by parts per thousand 44%.) and enriched in C-13 (by similar to 4.8 parts per thousand). Such inhomogeneous distribution of isotopes in chlorophylls suggests that (1) the phytol in chlorophylls reflects strong D- and C-13-depletions due to the isotopic fractionations during the methylerythritol phosphate pathway followed by hydrogenation, and (2) the chlorophyllides reflect D- and (13)Genrichments in tricarboxylic acid cycle. On the other hand, chlorophylls are slightly (similar to 1.2 parts per thousand) depleted in N-15 relative to the bulk tissue, indicating that net isotopic fractionation of nitrogen during chlorophyll biosynthesis is small compared with those of hydrogen and carbon. (c) 2005 Elsevier Ltd. All rights reserved.