Tropospheric ozone (O3) 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 O3 (250 vs. 0 ppb, 5 h day−1 for 2 weeks) were monitored in two chlorolichens with different ecology, Parmotrema perlatum and Xanthoria parietina. Modulated chlorophyll a fluorescence (ChlaF), superoxide anion radical (O2•−) and hydrogen peroxide (H2O2) production, antioxidant content and enzyme activity of the ascorbate/glutathione cycle were measured after exposure and, for ChlaF, 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. O3 slightly modified ChlaF parameters related to the controlled dissipation, with reduction of Fm, Fv/Fm (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 H2O2, glutathione (GSH) and oxidized glutathione (GSSG) (but not that of O2•− 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 O3-tolerant thanks to the constitutive antioxidant systems, intimately related to their poikilohydric life-style, is thus confirmed.

Ozone and desiccation tolerance in chlorolichens are intimately connected: a case study based on two species with different ecology

Candotto Carniel, Fabio;Incerti, Guido;Tretiach, Mauro
2018-01-01

Abstract

Tropospheric ozone (O3) 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 O3 (250 vs. 0 ppb, 5 h day−1 for 2 weeks) were monitored in two chlorolichens with different ecology, Parmotrema perlatum and Xanthoria parietina. Modulated chlorophyll a fluorescence (ChlaF), superoxide anion radical (O2•−) and hydrogen peroxide (H2O2) production, antioxidant content and enzyme activity of the ascorbate/glutathione cycle were measured after exposure and, for ChlaF, 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. O3 slightly modified ChlaF parameters related to the controlled dissipation, with reduction of Fm, Fv/Fm (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 H2O2, glutathione (GSH) and oxidized glutathione (GSSG) (but not that of O2•− 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 O3-tolerant thanks to the constitutive antioxidant systems, intimately related to their poikilohydric life-style, is thus confirmed.
23-giu-2017
Pubblicato
http://www.springerlink.com/content/0944-1344
File in questo prodotto:
File Dimensione Formato  
s11356-017-9444-0.pdf

Accesso chiuso

Tipologia: Documento in Versione Editoriale
Licenza: Copyright Editore
Dimensione 745.05 kB
Formato Adobe PDF
745.05 kB Adobe PDF   Visualizza/Apri   Richiedi una copia

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11368/2916153
Citazioni
  • ???jsp.display-item.citation.pmc??? 2
  • Scopus 8
  • ???jsp.display-item.citation.isi??? 7
social impact