Institute of Botany, Ecology Research Center, Avenue Miguel Estéfano, 3687, 04301-012, SP, Brazil.
Institute of Bioscience, University of São Paulo, Matão St. 257, 05508-090, SP, Brazil.
Sci Total Environ. 2021 May 15;769:145080. doi: 10.1016/j.scitotenv.2021.145080. Epub 2021 Jan 15.
Eugenia uniflora L. is an important fruit tree native to tropical South America that adapts to different habitats, thanks to its metabolic diversity and ability to adjust the leaf antioxidant metabolism. We hypothesized that this metabolic diversity would also enable E. uniflora to avoid oxidative damage and tolerate the enhanced ozone (O3) concentrations that have been registered in the (sub)tropics. We investigated whether carbohydrates, polyphenols and antioxidants are altered and markers of oxidative damage (ROS accumulation, alterations in leaf gas exchange, growth and biomass production) are detected in plants exposed to two levels of O (ambient air and twice elevated ozone level in a O-FACE system for 75 days). Phytotoxic O dose above a threshold of 0 nmol m s (POD0) and accumulated exposure above 40 ppb (AOT40) were 3.6 mmol m and 14.898 ppb h at ambient, and 4.7 mmol m and 43.881 ppb h at elevated O. Twenty-seven primary metabolites and 16 phenolic compounds were detected in the leaves. Contrary to the proposed hypothesis that tropical broadleaf trees are relatively O tolerant, we concluded that E. uniflora plants are sensitive to elevated O concentrations. Experimental POD0 values were lower than the critical levels for visible foliar O, because of low stomatal conductance. In spite of this low stomatal O uptake, we found classic O injury, e.g. reduction in carbohydrates and fatty acids concentrations; non-significant changes in the polyphenol profile; inefficient antioxidant responses; increased contents of ROS and indicators of lipid peroxidation; reductions in stomatal conductance, net photosynthesis, root/shoot ratio and height growth. However, we also found some compensation mechanisms, e.g. increased leaf concentration of polyols for protecting the membranes, and increased leaf number for compensating the decline of photosynthetic rate. These results help filling the knowledge gap about tropical tree responses to O.
三叶番樱桃是一种原产于南美洲热带地区的重要果树，由于其代谢多样性和调节叶片抗氧化代谢的能力，能够适应不同的生境。我们假设这种代谢多样性也能使三叶番樱桃避免氧化损伤，并耐受在（亚热带）热带地区已经记录到的增强的臭氧（O3）浓度。我们研究了在暴露于两种 O 浓度（大气 O3 浓度和 FACE 系统中 O3 浓度增加两倍，共 75 天）下，植物的碳水化合物、多酚和抗氧化剂是否会发生变化，以及是否会检测到氧化损伤的标志物（ROS 积累、叶片气体交换、生长和生物量产生的变化）。当臭氧剂量超过 3.6mmol·m-2·s-1（POD0）和累计暴露量超过 40ppb·h（AOT40）时，会出现植物毒性；在大气条件下，POD0 和 AOT40 值分别为 3.6mmol·m-2·s-1 和 14.898ppb·h，在高 O3 条件下，POD0 和 AOT40 值分别为 4.7mmol·m-2·s-1 和 43.881ppb·h。在叶片中检测到 27 种初级代谢物和 16 种酚类化合物。与热带阔叶树相对耐 O3 的假设相反，我们得出结论，三叶番樱桃植物对高浓度 O3 敏感。实验中的 POD0 值低于可见叶 O3 的临界水平，因为气孔导度较低。尽管 O3 的气孔吸收量较低，但我们发现了典型的 O3 损伤，例如碳水化合物和脂肪酸浓度降低；多酚谱没有显著变化；抗氧化剂反应效率低下；ROS 含量和脂质过氧化指标增加；气孔导度、净光合速率、根/茎比和株高生长降低。然而，我们也发现了一些补偿机制，例如增加叶片中多元醇的浓度以保护细胞膜，增加叶片数量以补偿光合速率的下降。这些结果有助于填补热带树木对 O3 响应的知识空白。
