Species-specific differences in temporal and spatial variation in δ13C of plant carbon pools and dark-respired CO2 under changing environmental conditions

Abstract

Stable carbon isotope signatures are often used as tracers for environmentally driven changes in photosynthetic δ(13)C discrimination. However, carbon isotope signatures downstream from carboxylation by Rubisco are altered within metabolic pathways, transport and respiratory processes, leading to differences in δ(13)C between carbon pools along the plant axis and in respired CO(2). Little is known about the within-plant variation in δ(13)C under different environmental conditions or between species. We analyzed spatial, diurnal, and environmental variations in δ(13)C of water soluble organic matter (δ(13)C(WSOM)) of leaves, phloem and roots, as well as dark-respired δ(13)CO(2) (δ(13)C(res)) in leaves and roots. We selected distinct light environments (forest understory and an open area), seasons (Mediterranean spring and summer drought) and three functionally distinct understory species (two native shrubs-Halimium halimifolium and Rosmarinus officinalis-and a woody invader-Acacia longifolia). Spatial patterns in δ(13)C(WSOM) along the plant vertical axis and between respired δ(13)CO(2) and its putative substrate were clearly species specific and the most δ(13)C-enriched and depleted values were found in δ(13)C of leaf dark-respired CO(2) and phloem sugars, ~-15 and ~-33 ‰, respectively. Comparisons between study sites and seasons revealed that spatial and diurnal patterns were influenced by environmental conditions. Within a species, phloem δ(13)C(WSOM) and δ(13)C(res) varied by up to 4 ‰ between seasons and sites. Thus, careful characterization of the magnitude and environmental dependence of apparent post-carboxylation fractionation is needed when using δ(13)C signatures to trace changes in photosynthetic discrimination.

Diel variations in carbon isotopic composition and concentration of organic acids and their impact on plant dark respiration in different species

“…2). This is particularly important for the comparability of d 13 C R measurements taken over the diel cycle with the corresponding temperature changes, especially under field conditions (Sun et al 2009;Unger et al 2010;Dubbert et al 2012).…”

Progress and challenges in using stable isotopes to trace plant carbon and water relations across scales

“…More studies of the sensitivity of respiratory δ 13 C to changes in environmental conditions and between organs are needed, which will allow for a better understanding of temporal variability in post-photosynthetic fractionation (Dubbert et al, 2012) and could provide a basis for the use of respiratory δ 13 CO 2 as an indicator of physiological activity (e.g. Barbour et al, 2011a, b).…”

“…Repetitive sampling and isotope analysis of tissues and compounds which are known to integrate shorter and more defined time periods such as phloem sugars (e.g. Keitel et al, 2003, Dubbert et al, 2012 during the growing season, together with bulk leaf assessments, might help to better constrain the physiological meaning of 13 C b and 18 O b . For community scale stable isotope approaches (see Sect.…”

“…Keitel et al, 2003;Gessler et al, 2004;Scartazza et al, 2004;Barbour et al, 2005;Rascher et al, 2010;Ubierna and Marshall, 2011;Dubbert et al, 2012). A dual-isotope approach (δ 13 C and δ 18 O see Sect.…”

Spatial patterns of leaf δ13C and its relationship with plant functional groups and environmental factors in China

“…Recently, the importance of biochemical and physiological mechanisms in controlling the leaf δ 13 C values of plant tissue has got growing concern. The biochemical and physiological mechanisms include different carbohydrate storage strategies, coordination between stomatal conductance and photosynthetic capacity, and adjustment of leaf area to water‐conducting tissue [ Epron et al ., ; Dubbert et al ., ; Tcherkez et al ., ; Cernusak et al ., ].…”