Gao Feng, Catalayud Vicent, Paoletti Elena, Hoshika Yasutomo, Feng Zhaozhong
State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Shuangqing Road 18, Haidian District, Beijing 100085, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China.
Fundación CEAM, c/Charles R. Darwin 14, Parque Tecnológico, Paterna 46980 Valencia, Spain.
Environ Pollut. 2017 Nov;230:268-279. doi: 10.1016/j.envpol.2017.06.044. Epub 2017 Jun 27.
Tropospheric ozone (O) pollution frequently overlaps with drought episodes but the combined effects are not yet understood. We investigated the physiological and biomass responses of an O sensitive hybrid poplar clone ('546') under three O levels (charcoal-filtered ambient air, non-filtered ambient air (NF), and NF plus 40 ppb) and two watering regimes (well-watered (WW) and reduced watering (RW), i.e. 40% irrigation) for one growing season. Water stress increased chlorophyll and carotenoid contents, protecting leaves from pigment degradation by O. Impairment of photosynthesis by O was also reduced by stomatal closure due to water stress, which preserved light-saturated CO assimilation rate, and the maximum carboxylation efficiency. Water stress increased water use efficiency of the leaves while O decreased it, showing significant interactions. Effects were more evident in older leaves than in younger leaves. Water stress reduced biomass production, but the negative effects of O were less in RW than in WW for total biomass per plant. A stomatal O flux-based dose-response relationship was parameterized considering water stress effects, which explained biomass losses much better than a concentration-based approach. The O critical level of Phytotoxic Ozone Dose over a threshold of 7 nmol O.m.s (POD) for a 4% biomass loss in this poplar clone under different water regimes was 4.1 mmol m. Our results suggest that current O levels in most parts of China threaten poplar growth and that interaction with water availability is a key factor for O risk assessment.
对流层臭氧（O₃）污染经常与干旱事件重叠，但二者的综合影响尚不清楚。我们研究了一个对O₃敏感的杂交杨树无性系（‘546’）在三个O₃水平（活性炭过滤的环境空气、未过滤的环境空气（NF）和NF加40 ppb）以及两种浇水方式（充分浇水（WW）和减少浇水（RW），即40%灌溉量）下一个生长季的生理和生物量响应。水分胁迫增加了叶绿素和类胡萝卜素含量，保护叶片免受O₃引起的色素降解。水分胁迫导致气孔关闭，这也减少了O₃对光合作用的损害，从而保持了光饱和CO₂同化率和最大羧化效率。水分胁迫提高了叶片的水分利用效率，而O₃则降低了水分利用效率，二者表现出显著的相互作用。这种影响在老叶中比在幼叶中更明显。水分胁迫降低了生物量的产生，但对于单株植物的总生物量而言，O₃在RW条件下的负面影响小于WW条件。考虑到水分胁迫的影响，基于气孔O₃通量的剂量-反应关系被参数化，这比基于浓度的方法能更好地解释生物量损失。在不同水分条件下，该杨树无性系生物量损失4%时，超过7 nmol O₃·m⁻²·s⁻¹阈值的植物毒性臭氧剂量（POD）的O₃临界水平为4.1 mmol m⁻²。我们的结果表明，中国大部分地区目前的O₃水平威胁杨树生长，并且与水分可利用性的相互作用是O₃风险评估的关键因素。
