Physiological Aspects of Cadmium and Nickel Toxicity in the Lichens Peltigera rufescens and Cladina arbuscula Subsp. mitis

Abstract

This study was undertaken with the aim of investigating the effect of Cd 2+ and Ni 2+ containing solutions on selected physiological parameters (metal uptake, chlorophyll a fluorescence, assimilation pigment composition, thiobarbituric acid-reactive substance production, and ergosterol content) in the lichens Peltigera rufescens and Cladina arbuscula subsp. mitis growing on historic copper mine-spoil heaps at Ľubietová-Podlipa, Slovakia. Physiological measurements did not confirm significantly higher sensitivity to Cd and Ni of the cyanolichen P. rurescens compared to the green-algal lichen C. arbuscula subsp. mitis. Under natural conditions, C. arbuscula subsp. mitis is able to grow directly on copper mine heaps of Central Slovakia, while P. rufescens grows only on their margins. A crucial factor for this limited distribution of P. rufescens may be, at least in part, the higher intracellular accumulation of metals. Although lichen photobionts are generally regarded as key elements of lichen sensitivity, further research is necessary to elucidate this point since the higher levels of intracellular Cd and Ni do not allow to regard cyanobacterial photobionts of P. rufescens as more sensitive than the eukaryotic ones of C. arbuscula subsp. mitis.

Seasonal variations in intracellular trace element content and physiological parameters in the lichen Evernia prunastri transplanted to an urban environment

“…On the other hand, wear of tires, brakes, engine, and vehicle components is a well known source of Cd and Sb atmospheric pollution (Cadle et al 1997, Beckerman et al 2008). However, it should be considered that intracellular concentrations of Cd and Sb measured in the present study (range of seasonal average: Cd=0.03-0.08 µg g -1 dw, Sb=0.22-0.46 µg g -1 dw) were low and in line with intracellular values reported for lichens from unpolluted areas (Bačkor et al 2010, Paoli et al 2013b. Nevertheless, assuming Sb as a main tracer of traffic emissions, positive correlations emerged between Sb and Ba (r=0.52, p<0.05), Cr (r=0.65, p<0.001), Cu (r=0.66, p<0.001), Fe (r=0.37, p<0.05) and Zn (r=0.70, p<0.001), suggesting also that the intracellular content of these elements was partially associated with vehicular traffic.…”

The Impact of Cadmium on Photosynthetic Performance and Secondary Metabolites in the Lichens Parmelia sulcata, Flavoparmelia caperata and Evernia prunastri

“…However, a decrease was observed only eight days after the exposure suggesting the relative resistance of the lichen photobiont to short-term exposure to high Cd concentration. Bačkor et al (2010) also reported relatively low toxicity of Cd, compared to other metals, e.g. Cu in lichens Peltigera rufescens and Cladina arbuscula 24 h after the exposure.…”

“…In the last 20 years, chlorophyll fl uorescence measurements were successfully employed in various lichen studies investigating heavy metal pollution (Bačkor et al 2010, Karakoti et al 2014, Paoli et al 2015a). The maximum quantum yield of PSII (F v /F m ), besides being an important indicator of photosynthetic effi ciency, can indicate the vitality of a lichen photobiont (Paoli et al 2015a).…”

“…However, physiological responses of lichens to metals and their tolerance mechanisms are species-specifi c, ranging from relative resistance to high sensitivity. Exposure of lichens to metals can affect membrane integrity (Garty et al 2003, Pisani et al 2010, chlorophyll content Zetíková 2003, Carreras andPignata 2007), photosynthetic performance (Karakoti et al 2014, Paoli et al 2015a) and secondary metabolites (Hauck et al 2013, Gauslaa et al 2016. Among heavy metals, cadmium (Cd) is considered to be particularly toxic for various lichen species causing adverse physiological changes (Sanità di Toppi et al 2005).…”

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

“…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.…”