CO_(2)浓度增加和水分亏缺对典型绿肥植物光合性能及水分利用效率的影响

Effects of increasing CO_(2) concentration and water deficit on photosynthetic performance and water use efficiency of typical green manure plants

探讨大气CO_(2)浓度和水分变化对3种典型绿肥植物光合性能及水分利用效率的影响,可为未来气候变化情形下草地生态系统适应性管理提供理论支持。本试验利用可精准控制CO_(2)浓度的人工气候室,设置400(自然大气)和800μmol·mol^(-1)(倍增)两个CO_(2)浓度,80%土壤田间持水量(FC)(充分灌水对照)、55%~60%FC(轻度水分亏缺)、35%~40%FC(中度水分亏缺)、<35%FC(重度水分亏缺)4个水分梯度,研究CO_(2)浓度增加和水分亏缺对甘蓝型油菜、白三叶和紫花苜蓿叶绿素含量、气体交换参数及水分利用效率(WUE)的影响。结果表明:同一CO_(2)浓度下,与充分灌水对照相比,当土壤水分<40%FC时,3种植物的叶绿素含量和气体交换参数均显著降低;土壤水分为55%~60%FC时,3种植物的叶绿素总含量无显著变化,而白三叶和紫花苜蓿的光合速率(P_(n))、蒸腾速率(T_(r))降低了6%~25%,但WUE无显著性差异。与大气CO_(2)浓度相比,CO_(2)浓度倍增使充分灌水处理下甘蓝型油菜的P_(n)显著降低了21.5%,而显著增加了轻度水分亏缺下3种植物的P_(n),且增加了中度水分亏缺下甘蓝型油菜和紫花苜蓿的P_(n),但只对重度水分亏缺下紫花苜蓿的P_(n)有所改善;CO_(2)浓度倍增显著增加了白三叶和紫花苜蓿在所有水分处理下的WUE,但只增加了甘蓝型油菜在轻度水分亏缺下的WUE。CO_(2)浓度和水分的交互作用对3种植物的P_(n)均有显著影响,但仅对甘蓝型油菜的WUE有显著影响。综上,3种植物对大气CO_(2)浓度倍增和水分亏缺的响应存在明显差异,CO_(2)浓度升高能改善轻度水分亏缺对3种植物光合性能和WUE的不利影响,但只改善了重度水分亏缺下紫花苜蓿的光合性能。

Exploring the impacts of CO_(2)and soil water availability on the photosynthetic performance and water use efficiency of three green manure plants could provide theoretical basis for the adaptive management of grassland ecosystems under future climate change.An experiment was conducted in an artificial climate chamber with precisely controled CO_(2)concentrations of 400(natural atmospheric)and 800μmol·mol^(-1)(doubled),and four water treatments,80%field water holding capacity(FC)(full irrigation control group),55%-60%FC(mild water deficit),35%-40%FC(moderate water deficit),<35%FC(severe water deficit)to investigate the impacts of increasing CO_(2)concentration and water deficit on chlorophyll content,gas exchange variables,and water use efficiency(WUE)of oilseed rape(Brassica napus),white clover(Trifolium repens),and alfalfa(Medicago sativa).The results showed that under the same CO_(2)concentration,when soil moisture was less than 40%FC,the chlorophyll content and gas exchange parameters of three plants were significantly decreased.The treatment of 55%-60%FC did not alter the total chlorophyll content of three species,but reduced the photosynthetic rate(P_(n))and transpiration rate(T_(r))of white clover and alfalfa by 6%-25%and did not affect their WUE.Compared with atmospheric CO_(2)concentration,the doubled CO_(2)concentration significantly decreased the P_(n)of oilseed rape by 21.5%under the full irrigation treatment,increased the P_(n)of three species under mild water deficit,increased the P_(n)of oilseed rape and alfalfa under moderate water deficit,but only improved the P_(n)of alfalfa under severe water deficit.The doubled CO_(2)concentration significantly increased WUE of white clover and alfalfa under all water deficit conditions,but only increased WUE of oilseed rape under mild water deficit.Increasing CO_(2)concentration and water deficit significantly interacted to affect P_(n)of three species and the WUE of oilseed rape.In summary,the three species differed in their responses to doubled atmospheric CO_(2)concentration and different levels of water deficit.Our results suggested that elevated CO_(2)concentration could improve the adverse effects of mild water deficit on photosynthetic performance and WUE of three species,but only improve the photosynthetic performance of alfalfa under severe water deficit.