State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Hangzhou, 311300, China.
State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Hangzhou, 311300, China.
Environ Pollut. 2021 Sep 15;285:117194. doi: 10.1016/j.envpol.2021.117194. Epub 2021 Apr 27.
Frequent drought events and particulate matter pollution from vehicular exhaust seriously affect urban plant growth and provisioning of ecological services. Yet, how plants respond physiologically and morphologically to these two combined stressors remains unknown. Here, we assessed particle retention dynamics and plant morphology and physiology of Euonymus japonicus Thunb. var. aurea-marginatus Hort. under continuous drought with severe exhaust exposure. Our results showed that continuous drought insignificantly lowered particle retention in each of three size fractions by 1.02 μg·cm on average in the first 28 days, but significantly lowered total particle retention by 35.75 μg·cm on the 35th day. We observed evident changes in morphology, leaf mass per area (LMA), pigments, gas exchange in all stressed plants. Compared with single stress, combined drought and pollution caused earlier yellowing and shedding of old leaves, significantly lowered LMA by 1.21 mg·cm, caused a greater decline in pigments and net photosynthetic rate (P). Large particles may mainly explain pigment reduction, lower weekly LMA increases, and stomatal restriction, while coarse particles may be the main drivers of the decline in P. Continuous drought mediated the influence of all three particle sizes on some parameters, such as weakening the impact of total particles on LMA, strengthening the impact of fine particles on photosynthesis. Our findings suggest that drought accelerates the physiological responses of plants to exhaust pollution. Under controlled severe exhaust pollution conditions, the optimal time to maintain high particle retention during continuous drought without decline in physiological conditions for E. japonicus var. aurea-marginatus was 14 days. Some additional interventions after 14 days (it could be postponed appropriately under field conditions) may help ensure healthy growth of plants and retention of particulate matter.
频繁的干旱事件和机动车尾气中的颗粒物污染严重影响城市植物的生长和生态服务的供应。然而，植物如何在生理和形态上对这两种胁迫源做出响应仍不清楚。在这里，我们评估了连续干旱和严重废气暴露下扶芳藤（Euonymus japonicus Thunb. var. aurea-marginatus Hort.）的颗粒保留动力学以及植物形态和生理学特性。我们的研究结果表明，连续干旱在最初的 28 天内，每个大小等级的颗粒保留量平均降低了 1.02μg·cm，而在第 35 天则显著降低了 35.75μg·cm。我们观察到所有受胁迫植物的形态、叶面积比（LMA）、色素和气体交换都发生了明显的变化。与单一胁迫相比，干旱和污染的复合胁迫导致老叶更早变黄和脱落，显著降低了 1.21mg·cm 的 LMA，导致色素和净光合速率（P）显著下降。大颗粒可能主要解释了色素减少、每周 LMA 增加减少和气孔限制，而粗颗粒可能是 P 下降的主要驱动因素。连续干旱调节了所有三种颗粒大小对某些参数的影响，例如减弱了总颗粒对 LMA 的影响，增强了细颗粒对光合作用的影响。我们的研究结果表明，干旱加速了植物对废气污染的生理响应。在受控的严重废气污染条件下，连续干旱期间保持高颗粒保留率而不降低扶芳藤生理状况的最佳时间是 14 天。在 14 天后进行一些额外的干预（在田间条件下可以适当推迟）可能有助于确保植物的健康生长和颗粒的保留。
