Variability of ¹³C‐labeling in plant leaves

Abstract

The reported variability of isotope composition in (13)C-enriched leaves is critical, and should be taken into account in subsequent experimental investigations of environmental processes using (13)C-labeled plant tissues.

Laser spectroscopy steered 13C‐labelling of plant material in a walk‐in growth chamber

“…Therefore, any change in the δ 13 C‐CO 2 value of the chamber air at the early stage – whether from imperfect sealing of the chamber or from plant respiration from the unlabelled seeds – is difficult to compensate for. Nguyen Tu et al analysed chamber air samples taken at fixed time intervals with a mass spectrometer and reported a similar initial decrease in the δ 13 C‐CO 2 value. As most studies do not monitor the δ 13 C‐CO 2 value in the chamber air, such occurrences will frequently go undetected.…”

“…To use isotopic labelling methods in quantitative C flux tracing, it is essential that the applied plant material is uniformly labelled The labelled material thus needs to have a homogeneous δ 13 C value throughout all plants in the labelled experiment, as well as within plants. For intra‐plant homogeneity, metabolic (labile) and structural (stabile) components must have the same δ 13 C value.…”

“…Soong et al reported an average value of 4.46 atom % with a standard error of 0.02 atom % (corresponding to a δ 13 C value of 3175 ± 20‰) for labelled Andropogon gerardii grass, with no significant differences in the value of labile and structural plant components. Nguyen Tu et al labelled at δ 13 C 500‰ and obtained an average δ 13 C value of 450.1‰ with a standard deviation of 25.4‰ for ryegrass.…”

“…Intra‐plant and intra‐leaf variations in δ 13 C values are typically much larger in labelled material than in natural plants, where standard deviations typically do not exceed a few ‰ Intra‐plant variation can be influenced by leaf age (especially in woody species), light conditions, and water/nitrogen availability . Within leaves, leaf ribs have higher δ 13 C values than intercostal tissue In labelling experiments, several factors are reported to affect intra‐plant homogeneity with continuous methods.…”

“…Within leaves, leaf ribs have higher δ 13 C values than intercostal tissue In labelling experiments, several factors are reported to affect intra‐plant homogeneity with continuous methods. There is an effect of spatial variability within the chamber if light conditions are not controlled In addition, the level of enrichment and leaf age play a role, with larger variability when labelling at higher enrichments and early‐emerging leaves Homogeneity of the labelling is also influenced by the stability of δ 13 C‐CO 2 values in the ambient air: both diurnal and long‐term fluctuations have been found to be responsible for a large part of the variability in the δ 13 C‐CO 2 value of labelled material The growth substrate also affects the atmospheric δ 13 C‐CO 2 value, as carbon exchange with the soil results in a dilution…”