AbdElgawad Hamada, Peshev Darin, Zinta Gaurav, Van den Ende Wim, Janssens Ivan A, Asard Han
Laboratory for Molecular Plant Physiology and Biotechnology, Department of Biology, University of Antwerp, Antwerp, Belgium.
Laboratory of Molecular Plant Biology, KU Leuven, Leuven, Belgium.
PLoS One. 2014 Mar 26;9(3):e92044. doi: 10.1371/journal.pone.0092044. eCollection 2014.
Elevated CO2 concentrations and extreme climate events, are two increasing components of the ongoing global climatic change factors, may alter plant chemical composition and thereby their economic and ecological characteristics, e.g. nutritional quality and decomposition rates. To investigate the impact of climate extremes on tissue quality, four temperate grassland species: the fructan accumulating grasses Lolium perenne, Poa pratensis, and the nitrogen (N) fixing legumes Medicago lupulina and Lotus corniculatus were subjected to water deficit at elevated temperature (+3°C), under ambient CO2 (392 ppm) and elevated CO2 (620 ppm). As a general observation, the effects of the climate extreme were larger and more ubiquitous in combination with elevated CO2. The imposed climate extreme increased non-structural carbohydrate and phenolics in all species, whereas it increased lignin in legumes and decreased tannins in grasses. However, there was no significant effect of climate extreme on structural carbohydrates, proteins, lipids and mineral contents and stoichiometric ratios. In combination with elevated CO2, climate extreme elicited larger increases in fructan and sucrose content in the grasses without affecting the total carbohydrate content, while it significantly increased total carbohydrates in legumes. The accumulation of carbohydrates in legumes was accompanied by higher activity of sucrose phosphate synthase, sucrose synthase and ADP-Glc pyrophosphorylase. In the legumes, elevated CO2 in combination with climate extreme reduced protein, phosphorus (P) and magnesium (Mg) contents and the total element:N ratio and it increased phenol, lignin, tannin, carbon (C), nitrogen (N) contents and C:N, C:P and N:P ratios. On the other hand, the tissue composition of the fructan accumulating grasses was not affected at this level, in line with recent views that fructans contribute to cellular homeostasis under stress. It is speculated that quality losses will be less prominent in grasses (fructan accumulators) than legumes under climate extreme and its combination with elevated CO2 conditions.
二氧化碳浓度升高和极端气候事件是当前全球气候变化因素中不断增加的两个组成部分，它们可能会改变植物的化学成分，进而改变其经济和生态特征，例如营养质量和分解速率。为了研究极端气候对组织质量的影响，选取了四种温带草原物种：积累果聚糖的禾本科植物多年生黑麦草、草地早熟禾，以及固氮豆科植物天蓝苜蓿和百脉根，在环境二氧化碳浓度（392 ppm）和升高的二氧化碳浓度（620 ppm）下，于高温（+3°C）条件下使其遭受水分亏缺。总体观察发现，极端气候与升高的二氧化碳浓度共同作用时，其影响更大且更普遍。施加的极端气候使所有物种的非结构性碳水化合物和酚类物质增加，而使豆科植物的木质素增加，禾本科植物的单宁减少。然而，极端气候对结构性碳水化合物、蛋白质、脂质、矿物质含量及化学计量比没有显著影响。与升高的二氧化碳浓度共同作用时，极端气候使禾本科植物的果聚糖和蔗糖含量大幅增加，而不影响总碳水化合物含量，同时显著增加了豆科植物的总碳水化合物含量。豆科植物中碳水化合物的积累伴随着蔗糖磷酸合酶、蔗糖合酶和ADP - 葡萄糖焦磷酸化酶活性的提高。在豆科植物中，升高的二氧化碳浓度与极端气候共同作用降低了蛋白质、磷（P）和镁（Mg）含量以及总元素与氮的比率，同时增加了酚类、木质素、单宁、碳（C）、氮（N）含量以及C:N、C:P和N:P比率。另一方面，积累果聚糖的禾本科植物的组织组成在该水平下未受影响，这与近期关于果聚糖在胁迫下有助于细胞内稳态的观点一致。据推测，在极端气候及其与升高的二氧化碳浓度共同作用的条件下，禾本科植物（果聚糖积累者）的质量损失将比豆科植物不那么显著。
