自由空气中臭氧浓度升高对大豆的影响

Responses of soybean to free-air ozone concentration enrichment:a research review

人类活动导致的大气和气候变化将极大地改变作物未来的生长环境,其中一个显著的变化就是近地层空气污染物臭氧浓度的迅速上升:从工业革命前低于10nL/L上升到现在的50nL/L(夏季每天8h平均),最新预测这一浓度将在2015-2050年增加20%-25%,本世纪末将增加40%-60%。目前大气背景臭氧浓度已经超过敏感植物的伤害阀值(即40nL/L),广泛地造成农作物减产,而未来臭氧浓度增加将使这种影响变得更为严重。与封闭式和开顶式试验相比,FACE(free-air gas concentration enrichment)研究使用标准的作物管理技术,在完全开放的农田条件下运行,代表了人类对未来大气环境的最好模拟。作为人类食物蛋白的重要来源,大豆是世界上种植面积最大的双子叶植物,也是1年生C3作物的模式作物,同时也被认为对臭氧污染最为敏感的作物之一。美国伊利诺伊大学的大豆FACE(SoyFACE)是世界上第1个利用FACE技术开展农作物对高浓度臭氧(模拟本世纪中叶近地层臭氧浓度)响应和适应的多学科合作研究。在阐述气室研究的局限性和介绍SoyFACE运行特点的基础上,首次综述了FACE情形下高浓度臭氧对大豆光合特性、冠层结构、物质生产与分配、产量及其构成因素以及虫害等方面的影响,并比较了FACE与气室研究结果的异同点。SoyFACE研究清楚地表明臭氧对未来粮食安全的影响必须作为一个重要的全球变化因子来加以考虑。利用FACE技术深入开展臭氧及其与其它全球变化因子的互作对世界主要粮食作物的影响、机制和调控的系统研究,是该领域未来优先考虑的方向。

Global atmospheric and climatic changes as a result of human activities will significantly alter many elements of the future crop production environment.One of these changes is the rapid increase in tropospheric ozone concentration（[O3]）.Daily 8-h tropospheric [O3] has increased from approximately 10 nL/L prior to the industrial revolution to the current level of approximately 50 nL/L（8-h summer seasonal average）,and is estimated to increase further by 20%-25% between 2015 and 2050,and by 40%-60% by 2100.The current ambient [O3]is above critical thresholds（40 nL/L） in damaging sensitive crops,and causing substantial yield loss.Future increase in ozone level will worsen this damage.As a major source of food protein worldwide,soybean（Glycine max L.Merr.）,the most widely planted dicotyledonous crop and a model of C3 annual plants,is considered as one of the most sensitive crops to ozone exposure.Assessing the impact of the expected increase in ground-level [O3] on soybean is therefore of crucial importance for food security of the world in the near future.However,current assessments of the effects on soybean from changes in [O3] based on studies conducted in chambers such as growth cabinets,glasshouse or open-top chambers.These facilities modify environmental conditions such as temperature,sunlight,humidity,and hence there is uncertainty over how well they represent the real effects of ozone under conditions of mormal atmosphere coupling in the field.Compared with chamber studies,free-air gas concentration enrichment（FACE） experiment,conducted in fully open-air field condition using regional standard agronomic practices,represents the best simulations for future atmospheric environment.SoyFACE,located at the University of Illinois,USA,is the first interdisciplinary study in the world to investigate the response and adaptation of crops to elevated [O3] that will occur over the first half of this century using FACE technology for ozone fumigation.Based on the description of the limitation of chamber studies and operation feature of the SoyFACE facility,this review paper mainly focused on the effects of free-air ozone concentration enrichment on the photosynthesis,canopy structure,dry matter production and distribution,grain yield and its components,as well as insect herbivory of soybean crops,compared the similarities and differences between findings obtained by FACE and enclosure methodologies,and evaluated the interactive effects of ozone by development stages,elevated carbon dioxide concentration and stress treatments（e.g.,low nitrogen and extreme climatic events）.This fist FACE treatment of a food crop to elevated [O3]showed yield losses in soybean under fully open-air field conditions that are at least as large as those predicted from chamber studies.It also showed that the losses may be further exacerbated when elevated [O3] is combined with an extreme event.These findings clearly indicated that the impacts of ozone on future food security must be considered as an important factor of global change.The priority areas for future research include the impacts of ozone and its interactions with other elements of global change on major food crops under open-air fumigation conditions,as well as the mechanisms of such impacts and possible regulations in reducing the adverse impacts.