Premium
Metabolic origin of the δ 13 C of respired CO 2 in roots of Phaseolus vulgaris
Author(s) -
Bathellier Camille,
Tcherkez Guillaume,
Bligny Richard,
Gout Elizabeth,
Cornic Gabriel,
Ghashghaie Jaleh
Publication year - 2009
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.2008.02679.x
Subject(s) - phaseolus , botany , chemistry , biology , radiochemistry , horticulture
Summary• Root respiration is a major contributor to soil CO 2 efflux, and thus an important component of ecosystem respiration. But its metabolic origin, in relation to the carbon isotope composition (δ 13 C), remains poorly understood. • Here, 13 C analysis was conducted on CO 2 and metabolites under typical conditions or under continuous darkness in French bean ( Phaseolus vulgaris ) roots. 13 C contents were measured either under natural abundance or following pulse‐chase labeling with 13 C‐enriched glucose or pyruvate, using isotope ratio mass spectrometer (IRMS) and nuclear magnetic resonance (NMR) techniques. • In contrast to leaves, no relationship was found between the respiratory quotient and the δ 13 C of respired CO 2 , which stayed constant at a low value ( c . –27.5‰) under continuous darkness. With labeling experiments, it is shown that such a pattern is explained by the 13 C‐depleting effect of the pentose phosphate pathway; and the involvement of the Krebs cycle fueled by either the glycolytic input or the lipid/protein recycling. The anaplerotic phospho enol pyruvate carboxylase (PEPc) activity sustained glutamic acid (Glu) synthesis, with no net effect on respired CO 2 . • These results indicate that the root δ 13 C signal does not depend on the availability of root respiratory substrates and it is thus plausible that, unless the 13 C photosynthetic fractionation varies at the leaf level, the root δ 13 C signal hardly changes under a range of natural environmental conditions.