Gas chromatography/isotope ratio mass spectrometry of leaf wax n‐alkalines from plants of differing carbon dioxide metabolisms

Abstract

Individual n-alkanes isolated from the leaf-surface waxes of plants utilizing differing photosynthetic pathways were analysed using gas chromatography/isotope ratio mass spectrometry (GC/IRMS), in order to obtain the ratios of I3C to I2C (S13C). Marked differences in the average '3C-depletion of the n-alkanes relative to whole leaf tissues were observed (C,= -7.%; C4= -9.90/,; CAM = -1%). Additionally, all three metabolic types exhibited considerable differences of 13C-depletion between n-alkane homologues isolated from the same plant.The technique of connecting a gas chromatograph to an isotope ratio mass spectrometer via a combustion interface' (GC/IRMS or irmGC/MS) allows for the calculation of the ratios of the stable isotopes of carbon ("C and 13C) for individual compounds within complex r n i x t u r e~.~~~'~ This ratio is expressed relative to a standard and calculated according to the equation:Where'3Cstandard/12Cstandard = 0.0112372 based On a belemnite from the Pee Dee formation (PDB). Due to the only relatively recent availability of commercial GC/IRMS instruments, there are few 6I3C values for individual plant compounds, such as those within lipid mixtures. Previous research on the 13C-depletion of lipids relative to source carbon (e.g., saccharides) has indicated that fatty acids have 6I3C values 3-5%, more negative than the s o u r~e .~'~,~ However, work by Rieley et aL3 has indicated that individual n-alkanes, and thus long-chain (> C,,) plant acyl lipids in general, could be more depeleted in 13C than might be expected from these general studies, and from published measurements on total lipids of higher plants in particular .8,9* lo. " The aim of this study has been to utilize GC/IRMS to investigate the relationship of leafwax lipid 613C values from plants of various metabolisms, and especially leaf-wax lipids derived from the acetate-malonate pathway,'* to bulk leaf 6I3C and bulk leaf-wax 613C values. n-Alkanes are likely to provide an adequate guide to the 6I3C composition of the homologous families of plant acyl lipids, which are closely related biosynthetically. EXPERIMENTAL Plant materialThe following plants were chosen for this study: Selenecerus grand$orus (Cactaceae), Tillandsia usneoides (Bromeliaceae), and Aechmeade albata (Bromeliaceae) representing CAM ( = crassulacean acid metabolism) species, and Psidzurn cattleionurn (Myrtaceae), Jacobinia cornea (Acanthaceae), Cyperus diffu-* Author to whom correspondence should be addressed. sus (Cyperaceae), Dendrocalamus strictus (Gramineae) and Cyperus alternifolius (Cyperaceae) representing C, plants. All leaves were harvested on 7 November 1991 from a well-ventilated glasshouse with the approximate dimensions of 10m by 40m and 5 m in height. In addition, the following plants were collected in the open: Succharum oficinarum (Gramineae), Miscanthus sacchariflorum (Gramineae) and Zea mays cv. dentiformis (Gramineae), representing C, plants. All plants were taken from the collection at the University of Bristol Botanical Gardens, Bristol, UK. Sam...

Possible algal origin of long chain odd n-alkanes in immature sediments as revealed by distributions and carbon isotope ratios

“…The corrected isotopic compositions observed for the C 27 , C 29 , C 31 and C 33 n-alkanes from maize, averaging at -18.6‰, and wheat, averaging at -35.0‰ (Table 1 and Fig. 2) are similar to those previously observed for n-alkanes from various C 4 and C 3 higher plants, respectively (Rieley et al, 1991(Rieley et al, , 1993. Markedly different ratios, averaging at -30.5‰, are obtained for the odd-carbon numbered n-alkanes of Pula sediment extract.…”

Soil n‐alkane δ13C along a mountain slope as an integrator of altitude effect on plant species δ13C

“…Leaf wax lipids during biosynthesis become more depleted in 13 C than the total biomass so that their d 13 C values vary between À31% and À39% in C 3 plants and between À18% and À25% in C 4 plants [Rieley et al, 1991[Rieley et al, , 1993Collister et al, 1994]. At present there is no reported investigation on the C 3 vs. C 4 plants distribution along the eastern slope of Mt.…”

Terrigenous plant wax inputs to the Arabian Sea: Implications for the reconstruction of winds associated with the Indian Monsoon

“…C 4 plants have a δ 13 C of −10 to −16 (Collister et al, 1994). Lipids are depleted in 13 C relative to bulk plant tissue by 4 − 8 (Rieley et al, 1991(Rieley et al, , 1993Collister et al, 1994;Chikaraishi et al, 2004). The compounds utilized for this study, n-alkanoic acids, exhibit isotopic compositions of −38 for C 3 plants and −20 for C 4 plants (Chikaraishi et al, 2004).…”

“…δ 13 C values for the C 30 alkanoic acid (hereafter δ 13 C 30 ) range from −21 to −27 , reflecting contributions from both C 3 and C 4 plants throughout the region (Rieley et al, 1991(Rieley et al, , 1993Collister et al, 1994;Chikaraishi et al, 2004). …”