Institute of Botany, University of Basel, Schönbeinstrasse 6, CH-4056 Basel, Switzerland.
Physiol Plant. 2010 Jul 1;139(3):241-55. doi: 10.1111/j.1399-3054.2010.01360.x. Epub 2010 Jan 25.
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.
半纤维素约占全球干燥植物生物质的四分之一，是仅次于纤维素的第二大丰富生物质成分。尽管它们在数量上很重要，但半纤维素对半纤维素对大气碳供应过剩的响应仍知之甚少，尽管随着二氧化碳浓度的增加，半纤维素可以作为碳汇。本研究旨在通过实验操纵植物的碳供应，阐明半纤维素作为碳汇的作用，类似于非结构性碳水化合物（NSC）。来自四个不同植物功能类型（草、草本植物、阔叶树和针叶树幼苗）的 16 种植物在温室中生长了 2 个月，大气 CO2 浓度分别极低（140 ppm）、中（280 ppm）和高（560 ppm），从而诱导大量 C 限制或 C 供应过剩的情况。所有物种和组织的地上和地下生物量以及非结构性碳水化合物均随着 CO2 浓度的增加而显著增加。除了 4 种草中的 2 种外，所有物种的叶片和木质组织中的总半纤维素浓度均随着 CO2 浓度的增加而显著增加，而 CO2 浓度的增加对半纤维素浓度没有显著影响。尽管总半纤维素浓度总体稳定，但随着 C 供应的增加，木质物种叶片中半纤维素的单糖谱显示葡萄糖单体显著增加。总之，新形成的生物量中的总半纤维素浓度似乎基本不受大气 CO2 浓度变化的影响，而随着 CO2 浓度的增加，阔叶树和针叶树幼苗叶片中半纤维素衍生的葡萄糖显著增加，表明不同半纤维素类在不同 CO2 浓度下对半纤维素的响应存在差异。
