Hemicellulose concentration and composition in plant cell walls under extreme carbon source-sink imbalances

Abstract

Hemicelluloses account for one-quarter of the global dry plant biomass and therefore are the second most abundant biomass fraction after cellulose. Despite their quantitative significance, the responsiveness of hemicelluloses to atmospheric carbon oversupply is still largely unknown, although hemicelluloses could serve as carbon sinks with increasing CO(2) concentrations. This study aimed at clarifying the role hemicelluloses play as carbon sinks, analogous to non-structural carbohydrates (NSC), by experimentally manipulating the plants' carbon supply. Sixteen plant species from four different plant functional types (grasses, herbs, seedlings of broad-leaved trees and conifers) were grown for 2 months in greenhouses at either extremely low (140 ppm), medium (280 ppm) or high (560 ppm) atmospheric CO(2) concentrations, thus inducing situations of massive C-limitation or -oversupply. Above and belowground biomass as well as NSC significantly increased in all species and tissues with increasing CO(2) concentrations. Increasing CO(2) concentrations had no significant effect on total hemicellulose concentrations in leaves and woody tissues in all species, except for two out of four grass species, where hemicellulose concentrations increased with atmospheric CO(2) supply. Despite the overall stable total hemicellulose concentrations, the monosaccharide spectra of hemicelluloses showed a significant increase in glucose monomers in leaves of woody species as C-supply increased. In summary, total hemicellulose concentrations in de novo built biomass seem to be largely unaffected by changed atmospheric CO(2) concentrations, while significant increases of hemicellulose-derived glucose with increasing CO(2) concentrations in leaves of broad-leaved and conifer tree seedlings showed differential responses among the different hemicellulose classes in response to varying CO(2) concentrations.

Chemical composition and antioxidant activity of leaves of mycorrhized sea-buckthorn ( Hippophae rhamnoides L.)

“…A common significant source of HCEL are cereal grains, herbs, and vegetables (Biel and Jacyno, 2014;Černiauskiene et al, 2014). Schädel et al (2010) examined four herb species (Geum urbanum L., Leontodon hispidus L., Salvia pratensis L., Silene flos-cuculi (L.) Greuter & Burdet) and reported HCEL content between the range of 60-220 g kg -1 DW. These authors found higher concentrations in silene, while the lowest HCEL concentrations were measured in leaves of geum, leontodon, and salvia, at less than 10% DW.…”

Growth reduction after defoliation is independent ofCO2supply in deciduous and evergreen young oaks

“…Such limitations were deliberately avoided in the current study by supplying sufficient amounts of nutrients and water throughout the experiment. The strong decrease in growth of undefoliated saplings at 160 ppm CO 2 in the current study thus indicates C limitation, comparable to a previous study with different functional plant types (Schädel et al ., ).…”

Influence of litter chemistry and stoichiometry on glucan depolymerization during decomposition of beech (Fagus sylvatica L.) litter

“…xylans, arabinoxylans, galactomannans). Hemicelluloses in beech contain only traces of glucose (<1%) and are mainly composed of xylose (65%), arabinose (20%) and galactose (15%), and therefore are not subsumed under glucans (Schaedel et al., 2010). Free glucose comprises the free, mostly cytosolic and vacuolar pool of unbound dissolved glucose, as contrasted by bound glucose such as that contained in disaccharides (e.g.…”