Differences Between Sensitivity of Mycobiont and Photobiont of Cladonia sp. Lichens to Different Types of Nitrogen Exposure

Abstract

Lichens absorb water, gases, dissolved substances, and especially pollutants by the entire surface, and they are considered to be the indicators of air quality. In our experiment, a sensitivity of Cladonia arbuscula subsp. mitis and Cladonia furcata lichens with the same photobiont Trebouxia was tested to nitrogen excess through a sensitivity of both the photobiont and mycobiont. Lichen ecophysiological parameters like chlorophyll a fluorescence, chlorophyll a integrity, the content of photosynthetic pigments, ergosterol, soluble proteins, thiobarbituric acid reactive substances, and secondary compounds were measured during two experiments that differed in time of nitrogen exposure. In the short-term experiment, also higher nitrogen concentrations were used to evaluate the dependence of different nitrogen concentrations. In the short-term experiment, lichens were soaked at the different solutions of ammonium nitrate (NH 4 NO 3 ) for describing an immediate effect of range of NH 4 NO 3 concentrations. In the long-term experiment, lichens were sprayed with low NH 4 NO 3 concentrations for 3 months for evaluating the effect of naturally occurring low nitrogen concentrations. Results showed that lichens responded differently in spite of having the same photobiont. The mycobiont of C. arbuscula subsp. mitis was more sensitive than mycobiont of C. furcata. In higher nitrogen concentrations, the photobiont of C. furcata was more sensitive than C. arbuscula subsp. mitis photobiont. Both lichens exhibited signs of damage; therefore, we conclude that they are sensitive to nitrogen excess, while C. arbuscula subsp. mitis is more sensitive species. The secondary compound content did not change in neither of lichen species. Cladonia sp. response to nitrogen excess depends on length and nitrogen dose exposure.

The Impact of Nitrogen Pollution in the Agricultural Landscape on Lichens: A Review of Their Responses at the Community, Species, Biont and Physiological Levels

“…According to Munzi et al [48], the fungal partner is more affected by nitrogen stress than the autotroph biont. Masla ňáková et al [12] also confirmed that it is the fungal partner in lichen thalli that governs the sensitivity of lichens to excess nitrogen. The greater sensitivity of the mycobiont than the photobiont to fertilization was evidenced by lower losses of chlorophyll a than ergosterol when exposed to 0.34 M NH 4 Cl [31].…”

“…Schrad. [12]. Nitrogen fertilization probably lowered the content of photosynthetic pigments (chorophyll a, b and carotenoids) in Evernia prunastri [18].…”

“…The main sources of nitrogen in the agricultural landscape are ammonia (NH 3 ) and the ammonium cation (NH 4 + ). Agricultural activities, principally livestock farming, the application of organic and mineral fertilizers, and biomass burning, contribute significantly to emissions of these compounds [5][6][7][8][9][10][11][12].…”

“…Nitrogen oxides NO X are further important, deposited atmospheric nitrogen compounds [12]. These reactive gases are derived from natural and anthropogenic sources, the main ones being road vehicle exhausts and industrial processes based on high-temperature combustion [3,5,12,[16][17][18][19]. In contrast to NH 3 , nitrogen oxides are only slowly deposited but can be transported over considerable distances [5,19].…”

“…Masla ňáková et al [12] found that the photosynthetic parameters in Cladonia arbuscula ssp. mitis (Sandst.)…”