不同水分条件下CO_2浓度升高对冬小麦碳氮转运的影响

Effects of elevated CO_2 concentration on accumulation and translocation of carbon and nitrogen of winter wheat under different water conditions

CO2浓度升高对作物的影响日益受到重视,水分是作物生长的必要条件之一。冬小麦是我国的主要粮食作物之一,阐明高CO2浓度和水分条件互作对冬小麦碳氮转运的影响,对客观认识气候变化背景下作物的水分管理及肥料施用具有实际指导意义。本研究利用开放式CO2富集系统(FACE)平台,以冬麦品种‘中麦175’为试验材料,采用盆栽试验方法,研究了不同CO2浓度[正常浓度(391±40)μmol·mol?1和高浓度(550±60)μmol·mol?1]及水分条件(湿润条件和干旱条件,即75%和55%田间土壤最大持水量)的冬小麦花前碳氮积累及花后碳氮转运的规律特征。结果表明:湿润条件下,与正常CO2浓度相比,高CO2浓度促进冬小麦地上部干物质及碳氮积累,开花期增幅分别为18.1%、16.5%、14.9%,成熟期增幅分别为6.6%、1.3%、4.5%,并提高碳氮转运能力及对籽粒贡献率,转运量、转运率及对籽粒贡献率的增幅碳素依次为39.3%、20.0%、30.0%,氮素依次为19.1%、3.8%、10.8%。干旱条件下,与正常CO2浓度相比,高CO2浓度对地上部碳氮积累有一定的促进作用,开花期和成熟期碳积累量分别增加3.0%和10.7%,氮积累量分别增加0和15.8%;但高CO2浓度阻碍了碳氮的转运,转运量、转运率降幅碳素分别为10.2%、12.8%,氮素分别为7.2%、7.1%;碳氮对籽粒贡献率则变化不同,碳降低14.4%,而氮升高31.3%。干旱及高CO2浓度互作与湿润条件正常CO2浓度处理相比,冬小麦碳素转运对籽粒贡献率降低更明显,地上部碳素转运量、转运率及对籽粒贡献率降幅分别为36.2%、16.9%、22.3%,但提高了氮素转运对籽粒贡献率,氮素转运量及转运率分别降低35.7%、15.2%,对籽粒贡献率增加7.0%。综合而言,高CO2浓度可促进冬小麦碳氮积累及其在花后向籽粒的转运,水分不足可能成为主要的物质转运障碍因子,限制CO2促进作用发挥。

Water is one of the necessary resources of crop growth. The effects of elevated CO2 concentration on crops have increasingly attracted the attention of scientist and policy makers in recent decades. As one of the main cultivated food crops in China, winter wheat’s response to elevated CO2 concentration under different water conditions was important for food safety in the future of China. The aim of this study was to explore the interactive effects of elevated CO2 concentration and soil moisture on translocations of carbon and nitrogen in winter wheat. The results of the study were to guide the appropriate practice of fertilizer and water managements of winter wheat under future climate change. A pot experiment was conducted with ‘Zhong Mai 175’ wheat variety as the materials in the free air CO2 enrichment （FACE） system. The research explored carbon and nitrogen accumulation during pre-anthesis and the related translocation during post-anthesis under different CO2 concentrations [ambient CO2 concentration of （391±40） μmol·mol^-1 and elevated CO2 concentration of （550±60） μmol·mol^-1] and soil moisture conditions （wet and drought conditions at 75% and 55% field capacity）. The results showed that compared with ambient CO2 concentration, elevated CO2 concentration increased dry matter and carbon and nitrogen accumulation in winter wheat under wet soil condition. The increase in dry matter and carbon and nitrogen accumulation was respectively 18.1%, 16.5% and 14.9% at flowering stage and 6.6%, 1.3% and 4.5% at maturity stage. The translocation and contribution to grain of carbon and nitrogen were also enhanced. Carbon translocation, translocation rate and contribution rate to grain increased respectively by 39.3%, 20.0% and 30.0%. Also nitrogen translocation, translocation rate and contribution rate to grain increased respectively by 19.1%, 3.8% and 10.8%. Under dry soil condition, compared with ambient CO2 concentration, elevated CO2 concentration increased carbon and nitrogen accumulation in winter wheat. Carbon and nitrogen accumulation increased respectively by 3.0% and 0, 10.7% and 15.8% at flowering, maturity stages. However, elevated CO2 concentration hindered the process of carbon and nitrogen translocation and reduced carbon contribution to grain. Carbon translocation, translocation rate and contribution rate respectively decreased by 10.2%, 12.8% and 14.4%. Nitrogen translocation and translocation rate decreased respectively by 7.2%, 7.1%; while nitrogen contribution rate to grain increased by 31.3%. Under the interaction of drought and elevated CO2 concentration, carbon translocation rate to grain significantly decreased while nitrogen translocation rate to grain increased, compared with wet and ambient CO2 concentration. Carbon translocation, translocation rate and contribution rate to grain decreased respectively by 36.2%, 16.9% and 22.3%. Nitrogen translocation and translocation rate decreased respectively by 35.7% and 15.2%, while nitrogen contribution rate to grain increased by 7.0%. In summary, elevated CO2 concentration promoted the accumulation of carbon and nitrogen and was conducive to carbon and nitrogen translocation after anthesis. Water stress was the main factor that hindered material translocation and thereby mitigated the positive effects of elevated CO2 concentration on winter wheat production.