1,721,004 research outputs found
How nitrogen changes protein expression in Cladonia portentosa: the effect of form, dose, time of exposure, and PK addition
No full textChlorophyll degradation and inhibition of polyamine biosynthesis in the lichen Xanthoria parietina under nitrogen stress
No full textThis study investigated if some nitrogen (N) compounds commonly used as fertilizers (KNO3, NH4NO3, (NH4)2SO4) cause chlorophyll degradation in the N-tolerant lichen Xanthoria parietina and if polyamines are responsible for the N-tolerance of this species. The results showed that N excess does not cause chlorophyll degradation and suggested the absence of kinetics in the mode of action of the N compounds tested. External supply of inhibitors of polyamine biosynthesis prior to N treatments did not cause any change in the response of chlorophyll integrity, suggesting that at least chlorophyll integrity is not controlled by polyamines
Epiphytic lichens as indicators of environmental quality in Rome
No full textA synthesis of the studies on lichen diversity carried out in Rome over the period 1982-2003 is presented. In this work, the Lichen Diversity (LD) method has been applied. Besides air pollution, the most important variable affecting the epiphytic lichen flora of Rome, currently updated to 102 taxa, is the influence of the Tyrrhenian Sea. Significant changes in the lichen flora have been noted over the past 20 years, with the lowest diversity now being found in the urban centre and in the eastern and southern sectors, while the "lichen desert" area has decreased in parallel with decreasing concentrations of CO, NOx and SO2
The integrity of lichen cell membrane is a suitable parameter for monitoring early biological effects of nitrogen pollution
No full textThis study aimed at testing the suitability of cell membrane integrity in the lichen Evernia prunastri (L.) Ach. as sensitive indicator of nitrogen (N) stress, to set up a rapid and effective method for monitoring biological effects of acute N pollution. Lichen samples were incubated in solutions of potassium nitrate, ammonium nitrate and ammonium sulphate at different concentrations, and cell membrane damage, expressed in terms of increased electrolyte leakage, was measured after 0, 24, 48 and 96 h. Cell membrane damage was observed in E. prunastri in the presence of high or very high N concentrations, irrespective of the compound supplied. Since the mycobiont represents the large majority of a lichen biomass, it is reasonable to assume that ion leakage mainly occurred from fungal cells. Although in biomonitoring studies the photobiont is usually regarded as the most sensitive partner of the lichen symbiosis, our findings suggest that the mycobiont is most affected in the case of N-excess, and that this feature can be used as suitable indicator of acute N stress episodes
Time- and dose-dependency of the effects of nitrogen pollution on lichens
No full textThe present work aims at testing if exposure time and dose play a role in the response of lichen species to nitrogen (N) pollution. To this purpose, samples of the N-sensitive Evernia prunastri and the N-tolerant Xanthoria parietina were treated for 5 weeks either with solutions of NH4NO3 0.05 and 1M, or (NH4)2SO4 0.025 and 0.5M. Photosynthetic efficiency was measured as an indicator of sample vitality. The results showed that the lowest concentrations were ineffective at the beginning, but after several supplies both compounds inhibited photosynthetic activity of E. prunastri. The highest concentrations had a deleterious effect, but with a temporal trend. For X. parietina no effect was found for the lowest concentrations, while the same trend shown by E. prunastri was instead observed following treatments with the highest concentrations. It was concluded that the response of lichens to N supply is not only species-specific, but also time- and dose-dependent. The results give a clue on field studies on the relationships between lichens and N pollution
Do polyamines alter the sensitivity of lichens to nitrogen stress
No full textThe sensitivity of lichens measuring photosynthetic efficiency and polyamines as modulator of nitrogen stress tolerance was investigated. Two lichen species with a markedly different tolerance to nitrogen compounds, namely Evernia prunastri (L.) Ach. and Xanthoria parietina (L.) Th.Fr., were incubated with deionized water (control) and solutions of KNO3, NH4NO3 and (NH4)2SO4 and then exposed to different light conditions. The Fv/Fm parameter (maximum quantum efficiency of photosystem II) was used as stress indicator. The results showed that Fv/Fm values, in the produced experimental conditions, were independent from the light gradient. Photosynthetic efficiency of E. prunastri was impaired by high ammonium concentrations, while nitrate had no effect; X. parietina was hardly influenced by nitrogen compounds. External supply of polyamines reduced the sensitivity of E. prunastri, while polyamine inhibitors reduced the tolerance of X. parietina to NH4+, suggesting that polyamines play an important role in modulating the sensitivity/tolerance to nitrogen stress
Physiological effects of a geothermal element: boron excess in the epiphytic lichen Xanthoria parietina (L.) TH. FR.
No full textThe results of a study aimed at investigating the effects of boron excess on a set of ecophysiological parameters in the lichen Xanthoria parietina, to set up a monitoring system to trace early biological effects of boron pollution in geothermal areas, are reported. To this purpose, lichen thalli have been incubated for 24 h in solutions at boron concentrations of 0.1, 1, 10 and 100 ppm, which were within the range in bulk deposition and geothermal fluids. The results showed a general trend of decreasing sample viability and increasing cell membrane damage and membrane lipid peroxidation under increasing boron concentrations, while photosynthetic efficiency, chlorophyll degradation and the contents of H2O2 and water-soluble proteins were not affected. It was argued that the fungal partner, that represents the large majority of the lichen biomass, is more sensitive to boron excess than the algal partner
Physiological response of the epiphytic lichen Evernia prunastri (L.) Ach. to ecologically relevant nitrogen concentrations
No full textThis study investigated the physiological response of the epiphytic lichen Evernia prunastri to ecologically relevant concentrations of nitrogen compounds. Lichen samples were sprayed for 4 weeks either with water or 50, 150 and 500 μM NH4Cl. The integrity of cell membranes and chlorophyll a fluorescence emission (FV/FM and PIABS) were analyzed. No membrane damage occurred after the exposure period. FV/FM, a classical fluorescence indicator, decreased during the second week of treatment with 500 μM \{NH4Cl\} and the third week with 50 and 150 μM NH4Cl. PIABS, an overall index of the photosynthetic performance, was more sensitive and decreased already during the first week with 500 μM \{NH4Cl\} and the second week with 150 μM NH4Cl. Since E. prunastri has been exposed to ammonium loads corresponding to real environmental conditions, these findings open the way to an effective use of this species as early indicators of environmental nitrogen excess
Physiological effects of a geothermal element: Boron excess in the epiphytic lichen Xanthoria parietina (L.) TH. FR
No full textThe results of a study aimed at investigating the effects of boron excess on a set of ecophysiological parameters in the lichen Xanthoria parietina, to set up a monitoring system to trace early biological effects of boron pollution in geothermal areas, are reported. To this purpose, lichen thalli have been incubated for 24 h in solutions at boron concentrations of 0.1, 1, 10 and 100 ppm, which were within the range in bulk deposition and geothermal fluids. The results showed a general trend of decreasing sample viability and increasing cell membrane damage and membrane lipid peroxidation under increasing boron concentrations, while photosynthetic efficiency, chlorophyll degradation and the contents of H2O2 and water-soluble proteins were not affected. It was argued that the fungal partner, that represents the large majority of the lichen biomass, is more sensitive to boron excess than the algal partner. © 2009 Elsevier Ltd. All rights reserved
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