Non-structural carbohydrates in woody plants compared among laboratories

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 R² = 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.This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by Oxford University Press. The published article can be found at: http://treephys.oxfordjournals.org/Keywords: soluble sugars, starch, particle size, reference method, standardization, non-structural carbohydrate chemical analysis, extraction and quantification consistenc

Assimilate allocation and carbon reserves in Juglans regia L. seedlings

International audienc

Modelling phloem transport within a pruned dwarf bean: a 2-source-3-sink system

A mechanistic model of carbon partitioning, based on the Munch hypothesis of phloem transport and implemented with PIAF-Munch modelling platform (Lacointe and Minchin 2008), was tested for an architecture more complex than any tested previously. Using C-11 to label photosynthate, responses in transport of photosynthate within a heavily pruned dwarf bean plant (Phaseolus vulgaris L.) to changes in source and sink activities were compared with model predictions. The observed treatment responses were successfully predicted. However, the observations could not be completely explained if the modelled stem contained only one phloem pathway: tracer from a labelled leaf was always detected in both shoot apex and root, whichever of the two leaves was labelled. This shows that bidirectional flow occurred within the stem, with solute moving simultaneously in both directions. Nevertheless, a model architecture with very little more complexity could incorporate such bidirectional flow. We concluded that the model could explain the observations, and that the PIAF-Munch model platform can be expected to describe partitioning in even more complex architectures

Growth relationships between root and shoot in walnut seedlings (Juglans regia L.)

International audienc

Storage and mobilization of carbon reserves in walnut and its consequences on the water status during winter

International audienc

Étude biologique et biochimique du déterminisme de la croissance rythmique du chêne pédonculé (Quercus robur L). Effets de l'ablation des feuilles

La croissance du chêne pédonculé cultivé à 25°C (± 1 °C) en jour long, est parfaitement rythmique. La suppression des limbes dont la taille est inférieure à 10 mm, la transforme en croissance continue. La suppression des feuilles d'un étage n ayant atteint leur taille définitive, provoque une très forte réduction en longueur de l'étage n + 1 lorsque celui-ci se développe. Au cours d'un flush, l'incorporation de la 14C-DMO (5-5' diméthyloxazolidine 2-4 dione), acide faible lipophile, par le bourgeon terminal, les tissus de l'axe sous-jacent au bourgeon terminal et les feuilles en croissance varie au cours du temps chez une plante intacte. Les résultats obtenus avec la fourniture de 14CO 2 au cours de la troisième vague de croissance confirment les résultats obtenus avec la 14C-DMO. Dans le cas d'une plante dont la croissance est devenue continue à la suite de l'ablation des très jeunes feuilles, le bourgeon accumule toujours plus de 14C-DMO que les entre-nœuds. Dans le cas de plantes où seule la croissance en longueur de l'étage est réduite par ablation des feuilles ayant atteint leur taille définitive, l'absorption de la 14C-DMO est identique à celle des témoins. L'ensemble des résultats permet de proposer une hypothèse explicative de la croissance rythmique du chêne pédonculé, basée sur la notion de puits.A biological and biochemical study of the factors determining rhythmical growth In pedunculate oak (Quercus robur). The effects of leaf removal. Quercus robur L showed perfect rhythmical growth when it was cultivated under controlled conditions at 25°C (± 1 °C), with long days or continuous light at 80 μmol·m-2·s-1. It was characterized by a regular succession of flushes. One flush lasted for 3 weeks: the first 2 weeks were the growing period and the last was the rest period. It was a false rest period because the activity of the apical meristem did not stop. A flush was characterized by the succession of scales and leaves, and by a succession of long and short internodes. The rhythmical growth is inhibited when 10 mm leaves are removed. Then continuous growth takes place. The apical meristem keeps producing a primortium. If a primortium is not removed it always gives a leaf and never a scale. The removal of the leaves of a flush at their adult size produces a strong reduction in the length of the next flush. During a flush, the intracellular concentration of the 14C-DMO (5 dimethyl oxazolidine 2-4 dione), a weak and lipophylacid, in the terminal bud and in itsadjacent axial tissues, and in leaves, varies in an untouched plant. The same variations are repeated for every flush. The results with a supply of 14CO2 confirm the results with the 14C-DMO. In the case of plants with continuous growth caused by the regular removal of young leaves, the intracellular concentration of 14C-DMO always remains higher in the terminal bud than in the internodes. There is no change in plants where only the adult leaves of a flush are removed. Our results allow us to put forward a nutritional hypothesis of the rhythmical growth of Quercus robur L. The rhythmical growth is the result of the relationships between 3 elements which are: the apical meristem, the axial tissues bearing the terminal bud, and the very young leaves. If one element, the axial tissues or the young leaves becomes stronger than the others, the growth is changed. Then it is possible that the internodes become short and the primordium produces scales

Growth relationships between root and shoot in walnut seedlings (Juglans regia L.)

National audienc