Bias in estimated online leaf carbon isotope discrimination due to woody tissues

Abstract

Branch or shoot chamber measurements integrate over both foliar and woody tissue carbon dioxide (CO2) fluxes and their associated influences on the carbon isotopic composition of atmospheric/headspace CO2. Here, we quantified the bias introduced by woody tissue carbon isotope fluxes on apparent leaf (13)C discrimination (Δ(13)Capparent) estimates, using laser spectroscopy under controlled conditions. CO2 efflux from woody tissues of defoliated beech saplings in the dark was strongly related to temperature (R(2) = 0.78), which served as the basis to model light-dependent woody tissue photosynthesis (R(2) = 0.72). We then quantified the contributions of leaf and woody tissues to leaf Δ(13)Capparent of foliated beech saplings in the light. Unbiased foliar Δ(13)C was 1.1 to 4.9‰ lower than leaf Δ(13)Capparent, depending on photosynthetic rates of woody tissues. Therefore, we strongly recommend accounting for isotope-related bias due to woody tissues when estimating leaf Δ(13)Capparent based on branch or shoot chamber measurements.

Special Issue dedicated to Professor Hanns-Ludwig Schmidt on the occasion of his 85th birthday

“…H.-L. Schmidt and his students and co-workers have contributed many fundamental findings to several fields of basic and applied stable isotope research, in plant biochemistry, human and animal physiology and ecology, environmental science, archaeology, paleoscience, forensics and food authenticity proofing. That diversity is also reflected in the contributions to this Special Issue by colleagues and by former students and co-workers [2][3][4][5][6][7][8][9][10][11][12][13]. Schmidt's own work included early studies on photosynthetic carbon isotope discrimination [14,15], which provides clues on the affiliation of plant species to photosynthetic types, and on limitations of discrete steps in the transfer of CO 2 from the air to RuBisCO in both C 3 and C 4 plants, and on the enzymatic mechanisms underlying post-photosynthetic carbon isotope discrimination phenomena.…”

“…One such finding with wide implications was the heterogeneous carbon isotope pattern in glucose [22] with a 13 C enrichment in the positions C-3 and C-4 which is caused by an equilibrium isotope effect on the aldolase reaction [23]. This pattern, also detectable in leaf soluble sugars and transitory starch [24], is responsible for the 13 C depletion of acetogenic lipids and the relationship between δ 13 C values of the fermentation products ethanol or acetic acid and that of the source sugar ( [10] and literature cited therein), and contributes to the 13 C enrichment of dark-respired CO 2 in plants ([25, see also [9,11]) and in connection with further isotope effects (e.g. [26]) to inter-and intra-molecular diversity of carbon isotope composition in plants (e.g.…”

Cellulose in Foliage and Changes during Seasonal Leaf Development of Broadleaf and Conifer Species

“…Among their many other uses, the stable isotope composition of foliage samples can provide crucial information about kinetic fractionation of water stable isotopes [6,7], light dependency of carbon isotopes and carbon discrimination [8,9], the response of foliage to elevated CO 2 [10], water use efficiency [11], leaf-level physiological processes across climatic gradients [12], litter production and litter turnover [13], the effects of canopy aging [14], and leaf development over a complete growing season [15,16]. Furthermore, foliage samples provide information essential to paleoclimate studies [17][18][19].…”