||Short-term dynamics of non-structural carbohydrates and hemicelluloses in young branches of temperate forest trees during bud break|
||Schädel Christina, Blöchl Andreas, Richter Andreas, Hoch Günter|
||Tree Physiology, in press|
Non-structural carbohydrates (NSC) are the most important C-reserves in tissues of deciduous and evergreen tree species. Beside NSC, cell-wall hemicelluloses as the second most abundant polysaccharides in plants have often been discussed to serve as additional mobile C-reserves during periods of enhanced carbon-sink activities. In order to assess the significance of hemicelluloses as mobile carbon reserves, branches of two deciduous (Carpinus betulus L., Fagus sylvatica L.) and two evergreen (Picea abies L., Pinus sylvestris L.) tree species were sampled in a mature mixed forest stand in short intervals before and during bud break to assess NSC and hemicellulose concentrations in response to the increased carbon demand during bud break. Starch concentrations in branch sapwood of deciduous trees strongly decreased immediately before bud break and increased after bud break. In both evergreen species, only small changes of NSC were found in branch sapwood. However, one-year old needles exhibited a significant increase in starch concentration shortly before bud break which declined again after flushing. Hemicellulose concentrations (on a NSC-free dry matter basis) in branch sapwood of Carpinus decreased significantly shortly before bud break but increased again after bud break. Contrarily, in Fagus branch sapwood hemicellulose concentrations remained constant during bud break. Moderate increases of total hemicellulose concentrations prior to bud break were found in one-year old needles of both conifers, which could be explained by an accumulation of glucose-units within the hemicellulose fraction. Overall, cell-wall hemicelluloses appeared to respond species specific to the enhanced carbon demand during bud break. Hemicelluloses in branch sapwood of Carpinus and in one-year old needles of conifers likely act as additional carbon reserves similar to starch.
||Günter Hoch: email | webpage|