Non-structural carbohydrates in woody plants compared among laboratories

Abstract

Non-structural carbohydrates (NSC) in plant tissue are frequently quantified to make inferences about plant responses to environmental conditions. Laboratories publishing estimates of NSC of woody plants use many different methods to evaluate NSC. We asked whether NSC estimates in the recent literature could be quantitatively compared among studies. We also asked whether any differences among laboratories were related to the extraction and quantification methods used to determine starch and sugar concentrations. These questions were addressed by sending sub-samples collected from five woody plant tissues, which varied in NSC content and chemical composition, to 29 laboratories. Each laboratory analyzed the samples with their laboratory-specific protocols, based on recent publications, to determine concentrations of soluble sugars, starch and their sum, total NSC. Laboratory estimates differed substantially for all samples. For example, estimates for Eucalyptus globulus leaves (EGL) varied from 23 to 116 (mean = 56) mg g(-1) for soluble sugars, 6-533 (mean = 94) mg g(-1) for starch and 53-649 (mean = 153) mg g(-1) for total NSC. Mixed model analysis of variance showed that much of the variability among laboratories was unrelated to the categories we used for extraction and quantification methods (method category R(2) = 0.05-0.12 for soluble sugars, 0.10-0.33 for starch and 0.01-0.09 for total NSC). For EGL, the difference between the highest and lowest least squares means for categories in the mixed model analysis was 33 mg g(-1) for total NSC, compared with the range of laboratory estimates of 596 mg g(-1). Laboratories were reasonably consistent in their ranks of estimates among tissues for starch (r = 0.41-0.91), but less so for total NSC (r = 0.45-0.84) and soluble sugars (r = 0.11-0.83). Our results show that NSC estimates for woody plant tissues cannot be compared among laboratories. The relative changes in NSC between treatments measured within a laboratory may be comparable within and between laboratories, especially for starch. To obtain comparable NSC estimates, we suggest that users can either adopt the reference method given in this publication, or report estimates for a portion of samples using the reference method, and report estimates for a standard reference material. Researchers interested in NSC estimates should work to identify and adopt standard methods.

Meta-analysis reveals that hydraulic traits explain cross-species patterns of drought-induced tree mortality across the globe

“…In particular, it would be valuable to examine the level and utility of carbon reserves during drought, which were related to mortality in some studies (28,29) but not in others (14,30). Currently, however, enormous methodological uncertainty with nonstructural carbohydrates measurements prohibits cross-study comparison (31). Although most of our analyses focused on species' relative mortality anomalies compared with the overall community mortality rate within a study, drought intensity was marginally significantly correlated with overall absolute mortality rate within a study (F = 3.17; df = 30; P = 0.08) (Fig.…”

Co‐occurring woody species have diverse hydraulic strategies and mortality rates during an extreme drought

“…However, in our current study, all species had very similar modelled NSC concentrations at the end of the growing season (Figure a). These values of NSC should, however, be considered approximate due to interlab variability (Quentin et al, ). Also, although photosynthesis was lowest in Juniperus during the driest month of the study (Figure c), photosynthesis was greatest over this period in Diospyros , a species that also experienced high mortality.…”

Lower photorespiration in elevated CO2 reduces leaf N concentrations in mature Eucalyptus trees in the field

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