Whole growing season pot experiments were conducted to examine the response of growth and water use efficiency (WUE) of spring wheat (Triticumaestivum L. cv. Gaoyuan 602) to CO2 enrichment. Wheat plants were grown in opentop chambers (OTCs) subject to two concentrations of CO2 (［CO2］)(350 and 700 μL/L, hereafter “ambient” and “elevated” respectively) and three soil water levels (80%, 60% and 40% field water capacity (FWC), hereafter “high soil moisture”, “medium soil moisture” and “low soil moisture”respectively). Elevated CO2 greatly increased leaf net photosynthesis (Pn) at all three soil water levels. The Pn of plants growing under elevated ［CO2］ was 22% lower than that of plants growing at ambient ［CO2］ when measured with the same ［CO2］ (700 μL/L). Plant growth was enhanced by elevated ［CO2］ throughout the growing season, with an increase of 14.8% in shoot dry weight at harvest under high soil moisture, and leaf area was increased by about 20% at all three soil water levels. Elevated ［CO2］ in combination with high soil moisture increased the ratio of plant shoot dry weight to height by 15.7%, while this ratio was decreased by over 50% when plants were subject to drought. Elevated ［CO2］ also increased the water use efficiency of wheat, mainly due to decreases in transpiration and cumulative consumption of water, and an increase in shoot dry weight, with the biggest value of 30% occurring at high soilwater moisture level. Compared to high soil moisture, drought decreased shoot dry weight by 72% under ambient ［CO2］, and by 76% under elevated ［CO2］. Similarly, drought also reduced WUE by 19% under ambient ［CO2］, and 23% under elevated ［CO2］. Our results indicate that: (1) elevated ［CO2］ can increase the photosynthetic rates, growth and WUE of wheat plants; (2) long term exposure to high ［CO2］ may result in lower photosynthetic capacity; (3) high ［CO2］ stimulates plants lateral growth more than vertical growth; (4) the effects of CO2 enrichment on plants depend on soil water status, with plants benefiting more from CO2 enrichment if sufficient water is supplied; and (5) drought may cause relatively more reduction in plant growth and WUE under future elevated ［CO2］ conditions.
CO2浓度升高和干旱对春小麦生长和水分利用的生态效应
吴冬秀1,2 王根轩3 白永飞1 廖建雄3 任红旭1
（1. 中国科学院植物研究所植物生态与多样性研究中心，北京100093；
2. 河南大学生物系，开封475001；3. 兰州大学干旱农业生态国家重点实验室，兰州730000）
摘要： 利用开顶式气室对春小麦进行了一个生长季的CO2倍增盆栽实验,土壤水分控制为3个水平(分别为田间持水量(FWC)的80%、60%、40%).结果显示,CO2倍增显著提高小麦的光合速率.但在相同的CO2测定浓度下, 生长在加倍CO2浓度下的小麦的光合速率比当前CO2浓度下小麦低22%.高CO2浓度显著促进小麦生长,相对增加幅度在适宜水分下最大,为14.8%.80%FWC水分条件下高CO2使植株的干重/高度比增加15.7%.高CO2条件下,小麦的蒸腾速率降低、累积耗水量减少、水分利用效率(WUE)提高,WUE的提高幅度在适宜水分下最大,为30%.干旱(40%FWC)使小麦地上干重和WUE在当前CO2条件下分别降低72%和19%,加倍CO2条件下降低幅度较大,分别为76%和23%.根据以上结果得出结论: (1) 高CO2条件下, 小麦的光合速率、地上生物量和水分利用效率提高;(2) 植物长期生长于高CO2浓度导致光合能力降低;(3) 高CO2对植物侧向生长的促进作用大于垂直生长,即高CO2下植株将相对粗壮;(4) 高CO2对植物的生态效应依赖于土壤水分,在适宜水分下相对较大;(5) 在未来高CO2条件下,干旱引起的减产和水分利用效率减低幅度将会更大.
关键词： CO2；开顶式气室；水分利用效率；春小麦；干旱
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