Hydrogen and carbon isotopic fractionations of lipid biosynthesis among terrestrial (C3, C4 and CAM) and aquatic plants

Compound-specific hydrogen and carbon isotopic compositions in n-alkanoic acids, phytol and sterols were determined for various plant classes (terrestrial C3-angiosperm; C3-gymnosperm; C4; crassulacean acid metabolism (CAM); and aquatic C3 plants) in order to investigate isotopic fractionations among various plant classes. In all plants, lipid biomolecules are depleted in both D (up to 324%,) and C-13 (Up to 14.7parts per thousand) relative to ambient water and bulk tissue, respectively. In addition, the magnitude of D- and C-13-depletion of lipid biomolecules is distinctive depending on plant classes. For example, C3 angiosperm n-alkanoic acids are less depleted in D (95 +/- 23parts per thousand) and C-13 (4.3 +/- 2.5parts per thousand) relative to ambient water and bulk tissue, respectively, while C4 plant n-alkanoic acids are more depleted in D (119 +/- 15parts per thousand) and C-13 (10.2 +/- 2.0parts per thousand). On the other hand, C3 angiosperm phytol and sterols are much more depleted in D (306 +/- 12parts per thousand for phytol, 211 +/- 15parts per thousand for sterol) with less depletion in C-13 (4.1 +/- 1.1parts per thousand for phytol, 1.3 +/- 0.9parts per thousand for sterol) relative to ambient water and bulk tissue, respectively, while C4 plant phytol and sterols are less depleted in D (254 +/- 7parts per thousand for phytol, 186 +/- 13parts per thousand for sterols) with much more depletion in C-13 (9.0 +/- 1.2parts per thousand for phytol, 5.0 +/- 1.1parts per thousand for sterols). Among various plant classes, there is a positive correlation between the D- and C-13-depletion for n-alkanoic acids, while a negative correlation was found for phytol and sterols from the same plants. (C) 2004 Elsevier Ltd. All rights reserved.