Understanding how ozone impacts plant water-use efficiency.
Understanding how ozone impacts plant water-use efficiency.
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了解臭氧如何影响植物用水效率。
DOI：
10.1093/treephys/tpab125
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发表时间：
2021
期刊：
影响因子：
4
通讯作者：
Cernusak LA
中科院分区：
文献类型：
--
作者：
Cernusak LA
对流层中的臭氧（O3）是一种重要的空气污染物，对全球植物和生态系统造成不利影响（Ainsworth等人，2012年; Grulke和Heath，2020年）。对流层O3通过O3前体的光化学反应自然地存在于大气中：氮氧化物（NOx），挥发性有机化合物（VOC），甲烷（CH 4）和一氧化碳（CO）。由于人类活动，这些O3前体的丰度可能会升高，例如车辆，工业过程和生物质燃烧的化学排放（Ainsworth等人，2020）。平均而言，由于快速的全球工业化和城市化，自1850年以来，地表[O3]增加了一倍多（Monks等人，2015年，Ainsworth 2017年）。这种增加的[O3]对气候的直接辐射强迫为+ 0.40 W m− 2，使O3成为继CO2和CH 4之后第三大人为温室气体（Ainsworth等人，2020）。目前的O3浓度已被证明会通过氧化应激导致叶细胞损伤，最终降低植物生长和植被群落的生产力（Ainsworth等人，2012年）。一项荟萃分析比较了暴露于环境[O3]（平均40 ppb）的北方温带树木与暴露于木炭过滤空气的树木，结果表明，O3使树木净光合作用和生物量分别降低了11%和7%（Wittig等人，2007，2009）。此外，一项多地点分析估计，从2000年到2010年，O3对欧洲森林初级生产总值的负面影响在0.4%到30%之间（Proietti等人，2016年）。暴露于高浓度[O3]也被证明会降低根系生长（Grulke等人，1998年），并改变可能影响水力传导性的茎材特性（Kaakinen等人，2004年）。因此，O3对植物生产力的负面影响是显著的，因此增加[O3]可以通过减缓CO2从大气到植被和土壤的转移来进一步促进气候变化（Sitch等人，2007）。尽管O3对植物生长及其基本组成过程的不利影响是众所周知的，但一些更微妙的复杂性尚未得到解决。一个例子是暴露于O3影响植物的水利用效率的方式。叶片水平的水分利用效率是指光合作用吸收的CO2与蒸腾作用向大气中损失的水分之间的比率（Bacon，2004年; Cernusak等人，2007年; Cernusak，2020年）。植物用水效率将碳循环和水循环联系起来，从而影响陆地生态系统的地球化学循环（Beer等人，2009年）。它也是作物改良工作中的一个重要目标参数（理查兹et al. 2002）。在这一期的《树木生理学》中，李等人。（2021）研究了暴露于一系列现实的[O3]对四种温带落叶树种水分利用效率的影响。他们的结果揭示了一个有趣的模式，在叶片水平上改变水分利用效率。
Ozone (O3) in the troposphere is an important air pollutant that causes adverse effects on plants and ecosystems worldwide (Ainsworth et al. 2012, Grulke and Heath 2020). Tropospheric O3 occurs in the atmosphere naturally through the photochemical reactions of O3 precursors: nitrogen oxides (NOx), volatile organic compounds (VOCs), methane (CH4) and carbon monoxide (CO). The abundance of these O3 precursors can be elevated due to anthropogenic activities, for example chemical emissions from vehicles, industrial processes and biomass burning (Ainsworth et al. 2020). On average, the surface [O3] has more than doubled since 1850 due to rapid global industrialization and urbanization (Monks et al. 2015, Ainsworth 2017). This increased [O3] has contributed to a direct radiative forcing of+ 0.40 W m− 2 on the climate, making O3 the third most significant anthropogenic greenhouse gas following CO2 and CH4 (Ainsworth et al. 2020). Current O3 concentrations have been shown to cause leaf cellular damage through oxidative stress, ultimately reducing plant growth and productivity of vegetation communities ( Ainsworth et al. 2012). A meta-analysis comparing northern temperate trees exposed to ambient [O3](on average 40 ppb) with those exposed to charcoal-filtered air suggested that O3 reduced net tree photosynthesis and biomass, by 11% and 7%, respectively (Wittig et al. 2007, 2009). Moreover, a multi-site analysis estimated the negative impact of O3 on gross primary production of European forests from 2000 to 2010 to range from 0.4% to 30%(Proietti et al. 2016). Exposure to elevated [O3] has also been shown to decrease root growth (Grulke et al. 1998), and to alter stem wood properties that could influence hydraulic conductivity (Kaakinen et al. 2004). Thus, the negative effects of O3 on plant productivity are significant, and increasing [O3] can therefore further contribute to climate change by slowing the transfer of CO2 from the atmosphere into vegetation and soils (Sitch et al. 2007).Although adverse effects of O3 on plant growth and its underlying component processes are generally well known, some of the more subtle intricacies have yet to be unraveled. One example is the way in which exposure to O3 impacts upon the water-use efficiency of plants. Water-use efficiency at the leaf level refers to the ratio between the uptake of CO2 by photosynthesis and the loss of water to the atmosphere by transpiration (Bacon 2004, Cernusak et al. 2007, Cernusak 2020). Plant water-use efficiency links carbon and water cycles, thereby influencing biogeochemical cycling of terrestrial ecosystems (Beer et al. 2009). It is also an important target parameter in crop improvement efforts (Richards et al. 2002). In this issue of Tree Physiology, Li et al.(2021) examined the impact of exposure to a range of realistic [O3] on water-use efficiency in four temperate, deciduous tree species. Their results revealed an intriguing pattern with respect to the alteration of water-use efficiency at the leaf level.