Effects of Ambient NO_x on Chlorophyll a Fluorescence in Transplanted Flavoparmelia caperata (Lichen)

Abstract

Transplants of Flavoparmelia caperata (L.) Hale were used to test possible relationships between chlorophyll a fluorescence (CaF) and ambient atmospheric conditions (temperature, precipitation, SO2 and NOx levels). Portions of the same thalli collected in a pristine site (A) of the Trieste Karst were exposed at that site, as the control, and in four other sites (B-E) in NE Italy, near to pollution monitoring stations. These sites had been selected in order to provide similar two by two climatic conditions (sites B,C: more humid; D,E: drier) and air pollution load (sites B,D: low; C,E: high). Before exposure and after 43 and 90 days of exposure, CaF measurements were carried out in the laboratory under controlled conditions. A classification of meteorological and pollution parameters recorded during exposure substantially confirmed the differences between site couplets. After 90 days, samples from sites A (control) and B (with very low pollution load) showed only slightly reduced NPQ, qN, Fo, and Fm values. Samples from site D, with medium air pollution load, and sites C,E, with high air pollution loads, showed proportionally greater variation for most of the CaF parameters. A highly significant correlation was found between NPQ, qN, Fm, and NOx pollution but not with SO2 or O3. Effects of NOx on lichens and possible action mechanisms are discussed. The results strongly suggest that CaF measurements of lichen transplants can be a valid tool in biomonitoring studies.

Monitoring Lichen as Indicators of Atmospheric Quality

“…The measurement of modulated chlorophyll a, fluorescence in lichens is one of several valid tools in biomonitoring studies (Jensen and Kricke 2000;Tretiach et al 2007b). The chlorophyll fluorescence parameter ratio of variable fluorescence to maximal fluorescence (Fv/Fm) has been widely used to assess the state of the photosynthetic apparatus in response air pollution (Bjerke et al 2005;Fernandez-Salegui et al 2006a;Tretiach et al 2007a;Paoli et al 2010;Piccotto et al 2011;Karakoti et al 2014).…”

“…The results of recent transplantation studies showed that the pulse amplitude modulation fluorimetry applied may become an important tool in biomonitoring studies. In such cases, particular care should be taken in sample collection, selection and exposure (Tretiach et al 2007b). …”

“…At the molecular level, Tretiach et al (2007b) reported that a large amount of NO x can damage the photobionts of transplanted Flavoparmelia caperata, hindering photosynthesis probably due to the increased reactive oxygen species (ROS), as high concentration of NO 2 in the cells forms nitrous and nitric acid, which acidifies cytoplasm and results in protein denaturation, deamination of amino acids and nucleic acid. When exposed to excessive nitrogen supply, the higher damage was observed for mycobiont than the photobiont (Dahlman et al 2002(Dahlman et al , 2003Gaio-Oliveira et al 2004).…”

The organic air pollutant cumene hydroperoxide interferes with NO antioxidant role in rehydrating lichen

“…However, air pollution impairs lichen colonization and survival (Barreno, 2002). SO 2 , O 3 and NO x have been related with lichen damage but the toxicity mechanisms overwhelming their extraordinary abiotic stress defence system have not been fully elucidated (Riddell et al, 2012(Riddell et al, , 2008Hauck et al, 2008;Tretiach et al, 2007;Kong et al, 1999;Ba ckor and Fahselt, 2003;Kong et al, 2002).…”

“…These features of lichens, combined with their extraordinary capability to grow in a large geographical range and accumulate mineral elements far above their needs, rank them among the best bioindicators (Garty et al, 2003). The ability of lichens to tolerate and even bioaccumulate heavy metals such as As, Pb or Cd, has been extensively studied (Bajpai and Upreti, 2012;State et al, 2012;Ba ckor et al, 2011;Pawlik-Skowronska and Ba ckor, 2011;Ba ckor et al, 2010) as well as the noxious effects of inorganic pollutants such as O 3 , SO 2 or NO x (Riddell et al, 2012;Hauck et al, 2008;Tretiach et al, 2007;Hauck, 2010). However, the toxic effects of volatile organic pollutants (VOPs) on lichens have not been addressed yet.…”