Department of Life Sciences, University of Trieste, Via L. Giorgieri 10, 34127, Trieste, Italy.
Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, 56124, Pisa, Italy.
Environ Sci Pollut Res Int. 2018 Mar;25(9):8089-8103. doi: 10.1007/s11356-017-9444-0. Epub 2017 Jun 23.
Tropospheric ozone (O) causes severe damage to many vascular plants but not to lichens. It was recently suggested that this may be due to their high levels of natural defences against the oxidative bursts associated to their fluctuating water content. In this study, the combined effects of watering regime (with or without a daily spray of distilled water), air relative humidity (20 ± 5 vs. 80 ± 5% RH) and O (250 vs. 0 ppb, 5 h day for 2 weeks) were monitored in two chlorolichens with different ecology, Parmotrema perlatum and Xanthoria parietina. Modulated chlorophyll a fluorescence (Chl F), superoxide anion radical (O) and hydrogen peroxide (HO) production, antioxidant content and enzyme activity of the ascorbate/glutathione cycle were measured after exposure and, for Chl F, after 1 and 2 days of recovery. The species differed in the antioxidant profile (ascorbate was higher in X. parietina, glutathione in P. perlatum), and in the activity of ROS-scavenging enzymes, more intense in the hygrophilous P. perlatum than in the meso-xerophilous X. parietina. O slightly modified Chl F parameters related to the controlled dissipation, with reduction of F, F/F (both species) and ETR (in P. perlatum), and increase in NPQ and qN (in X. parietina). It also influenced, particularly in P. perlatum, the content of HO, glutathione (GSH) and oxidized glutathione (GSSG) (but not that of O and AsA + DHA) and the activity of superoxide dismutase, ascorbate peroxidase and dehydroascorbate reductase. These parameters, however, were more heavily affected by water availability. The hypothesis that lichens are O-tolerant thanks to the constitutive antioxidant systems, intimately related to their poikilohydric life-style, is thus confirmed.
对流层臭氧 (O) 会对许多维管植物造成严重损害，但对地衣则不会。最近有人提出，这可能是由于它们具有高水平的天然防御机制，可以抵御与波动含水量相关的氧化爆发。在这项研究中，监测了两种生态差异较大的地衣（Parmotrema perlatum 和 Xanthoria parietina）在不同浇水制度（有或无每日蒸馏水喷雾）、空气相对湿度（20±5% 与 80±5% RH）和 O（250 与 0 ppb，5 小时/天，持续 2 周）条件下的综合效应。暴露后测量了调制叶绿素 a 荧光（Chl F）、超氧阴离子自由基（O）和过氧化氢（HO）的产生、抗氧化物含量和抗坏血酸/谷胱甘肽循环中的酶活性，并在暴露后 1 天和 2 天恢复时测量了 Chl F。这两种物种在抗氧化剂特征（X. parietina 中抗坏血酸较高，P. perlatum 中谷胱甘肽较高）和活性氧清除酶的活性（亲水性的 P. perlatum 比中湿性的 X. parietina 更强）方面存在差异。O 略微改变了与受控耗散相关的 Chl F 参数，导致 F、F/F（两个物种）和 ETR（在 P. perlatum 中）降低，而 NPQ 和 qN（在 X. parietina 中）增加。它还特别影响了 P. perlatum 中 HO、谷胱甘肽 (GSH) 和氧化型谷胱甘肽 (GSSG)（但不影响 O 和 AsA+DHA）的含量以及超氧化物歧化酶、抗坏血酸过氧化物酶和脱氢抗坏血酸还原酶的活性。然而，这些参数更容易受到水分供应的影响。因此，地衣之所以对 O 具有耐受性，是因为它们具有与变湿生活方式密切相关的组成性抗氧化系统，这一假说得到了证实。
