Post by ruth on May 3, 2009 11:04:31 GMT -5
Abstract
Thallus pieces of the Mn-sensitive epiphytic lichen Hypogymnia physodes and of the Mn-resistant Lecanora conizaeoides were incubated in 5 mM MnCl2 for 1 h. Element concentrations and thallus structure were subsequently studied with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray microanalysis. Mn concentrations both in fungal and algal cell walls and cell lumina were much lower in L. conizaeoides than in H. physodes, because the former immobilised Mn in the thallus (e.g. in polyphosphate granules) and in apothecia. Within the apothecia, Mn was deposited with phosphate in the hypothecium and in an unknown form in the asci. Effective immobilisation could cause the high Mn tolerance of L. conizaeoides. H. physodes also immobilised some Mn in extracellular particles in the upper cortex and in intracellular polyphosphate granules in the lower cortex. However, extra- and intra-cellular Mn concentrations in H. physodes increased much more during incubation with Mn compared with L. conizaeoides. The highest Mn concentrations were found in the upper and the lower cortex (i.e. in the cell walls and in the interhyphal polysaccharide matrix). The photobiont of H. physodes took up considerably less Mn than the mycobiont; this suggests that the latter is capable of protecting the photobiont to a certain extent from Mn invasion. Mn uptake released much Ca and Mg from H. physodes, especially from cortical cell walls and polysaccharide matrices. In the medulla, Mn was incorporated in Ca oxalate crystals especially on the surface of young growing hyphae. On a long-term basis, this is suspected to affect the integrity of the crystals, which fulfil important structural and physiological functions. Mn exposure decreased the Fe/Mn ratio more in H. physodes than in L. conizaeoides. As Fe is known to alleviate Mn toxicity in H. physodes, this could be a mechanism causing the higher Mn sensitivity of this species. Si/Mn ratios decreased in all thallus layers of H. physodes, but not of L. conizaeoides. Previous studies with soredia of H. physodes suggested possible alleviating effects of Si on Mn toxicity in lichens. Structural changes were observed in neither the mycobiont nor the photobiont of either lichen species.
Author Keywords: Ca oxalate crystals; Fe/Mn ratio; Heavy metal tolerance; Mn immobilisation; Polyphosphate granules; Trebouxia jamesii
Concentrations of chlorophylls a and b decreased with increasing MnCl2 supply in the epiphytic lichen Hypogymnia physodes, but not in Lecanora conizaeoides. The reduction of chlorophyll concentrations in H. physodes was as strong (chlorophyll a) or even stronger (chlorophyll b) as in samples treated with CuCl2. FeCl3 compensated for MnCl2-induced chlorophyll degradation in H. physodes. Furthermore, MnCl2-induced growth inhibition of soredia cultivated on agar plates was alleviated by FeCl3. These results suggest that Mn causes intracellular Fe deficiency in H. physodes. A soredia growth test with MnCl2 and KCl in combination proved that mitigating effects of FeCl3 were not just caused by reduced chemical activity of Mn2+ due to the addition of another salt. Furthermore, the test showed that Cl? did not inhibit soredia growth. High FeCl3 concentrations applied alone or in combination with MnCl2 were even more detrimental to H. physodes than MnCl2. MnCl2 did not affect the concentrations of ATP, ADP and AMP in H. physodes. This suggests that Mn uptake does not induce intracellular P deficiency in H. physodes despite that Mn is known to be immobilized with P in H. physodes in intracellular polyphosphate granules and in extracellular encrustations.
Author Keywords: Adenylate energy charge; ATP; Chlorophyll content; Heavy metal tolerance; Mn/Fe ratio; Soredia
Soredia of the lichen Hypogymnia physodes cultivated with Bold's basal medium on agar plates for 8 days exhibited decreasing growth rates along with increasing Mn concentrations above 3 mM. Ca and Mg added separately or in combination, alleviated Mn toxicity. The chlorophyll a and b content of the soredia was reduced under the influence of Mn and was positively correlated with the rate of grown soredia. Trebouxia cells of the soredia grown with excess Mn were smaller than control cells, had reduced chloroplasts and were partly collapsed; fungal hyphae were shortened and strongly swollen. Disintegrated cell walls occurred both in algal and fungal cells. Excess Mn was sequestered in extracellular encrustations together with phosphate as corresponding anion. Intracellularly, Mn was accumulated in polyphosphate granules both in algal and fungal cells. Mn uptake was correlated with significant loss of Na, Mg and Ca, particularly from the mycobiont. Fungal cell walls also lost significant amounts of P. The same damage symptoms occurred in cells of soredia both grown or not, but the former had a higher share of intact cells. Damaged cells of both types of soredia had equally increased Mn concentrations, whereas the total Mn content was higher in not grown soredia than in the grown ones due to the greater amount of damaged cells in the former. The Si-Mn ratio in cell walls of intact Trebouxia cells was significantly higher than in collapsed cells. The experimental evidence of Mn sensitivity of H. physodes soredia corresponds to studies of epiphyte vegetation in montane spruce forests of northern Germany that revealed decreasing cover values of H. physodes with an increasing Mn content of the substrate.
Author Keywords: Chlorophyll content; Heavy metal tolerance; Polyphosphate granules; Soredia; Trebouxia; X-ray microanalysis
Article Outline
1. Introduction
2. Materials and methods
2.1. Soredia growth
2.2. Chlorophyll content of soredia
2.3. Preparation for transmission and scanning electron microscopies
2.4. X-ray microanalysis in the transmission electron microscope
2.5. X-ray microanalysis in the scanning electron microscope
2.6. Statistics
3. Results
3.1. Soredia growth
3.2. Chlorophyll content of soredia
3.3. SEM studies
3.4. TEM studies
4. Discussion
Acknowledgements
References
www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T66-47PP6H3-4&_user=10&_origUdi=B6T66-4FRB7RW-1&_fmt=high&_coverDate=04%2F30%2F2003&_rdoc=1&_orig=article&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=7717e83604ee381dedbef93010f5579e
www.fs.fed.us/wildflowers/interesting/lichens/glossary.shtml
www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GX0-4K7WJ28-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=46fb80930d8d68f30497f80d76dc5ffc
Thallus pieces of the Mn-sensitive epiphytic lichen Hypogymnia physodes and of the Mn-resistant Lecanora conizaeoides were incubated in 5 mM MnCl2 for 1 h. Element concentrations and thallus structure were subsequently studied with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray microanalysis. Mn concentrations both in fungal and algal cell walls and cell lumina were much lower in L. conizaeoides than in H. physodes, because the former immobilised Mn in the thallus (e.g. in polyphosphate granules) and in apothecia. Within the apothecia, Mn was deposited with phosphate in the hypothecium and in an unknown form in the asci. Effective immobilisation could cause the high Mn tolerance of L. conizaeoides. H. physodes also immobilised some Mn in extracellular particles in the upper cortex and in intracellular polyphosphate granules in the lower cortex. However, extra- and intra-cellular Mn concentrations in H. physodes increased much more during incubation with Mn compared with L. conizaeoides. The highest Mn concentrations were found in the upper and the lower cortex (i.e. in the cell walls and in the interhyphal polysaccharide matrix). The photobiont of H. physodes took up considerably less Mn than the mycobiont; this suggests that the latter is capable of protecting the photobiont to a certain extent from Mn invasion. Mn uptake released much Ca and Mg from H. physodes, especially from cortical cell walls and polysaccharide matrices. In the medulla, Mn was incorporated in Ca oxalate crystals especially on the surface of young growing hyphae. On a long-term basis, this is suspected to affect the integrity of the crystals, which fulfil important structural and physiological functions. Mn exposure decreased the Fe/Mn ratio more in H. physodes than in L. conizaeoides. As Fe is known to alleviate Mn toxicity in H. physodes, this could be a mechanism causing the higher Mn sensitivity of this species. Si/Mn ratios decreased in all thallus layers of H. physodes, but not of L. conizaeoides. Previous studies with soredia of H. physodes suggested possible alleviating effects of Si on Mn toxicity in lichens. Structural changes were observed in neither the mycobiont nor the photobiont of either lichen species.
Author Keywords: Ca oxalate crystals; Fe/Mn ratio; Heavy metal tolerance; Mn immobilisation; Polyphosphate granules; Trebouxia jamesii
Concentrations of chlorophylls a and b decreased with increasing MnCl2 supply in the epiphytic lichen Hypogymnia physodes, but not in Lecanora conizaeoides. The reduction of chlorophyll concentrations in H. physodes was as strong (chlorophyll a) or even stronger (chlorophyll b) as in samples treated with CuCl2. FeCl3 compensated for MnCl2-induced chlorophyll degradation in H. physodes. Furthermore, MnCl2-induced growth inhibition of soredia cultivated on agar plates was alleviated by FeCl3. These results suggest that Mn causes intracellular Fe deficiency in H. physodes. A soredia growth test with MnCl2 and KCl in combination proved that mitigating effects of FeCl3 were not just caused by reduced chemical activity of Mn2+ due to the addition of another salt. Furthermore, the test showed that Cl? did not inhibit soredia growth. High FeCl3 concentrations applied alone or in combination with MnCl2 were even more detrimental to H. physodes than MnCl2. MnCl2 did not affect the concentrations of ATP, ADP and AMP in H. physodes. This suggests that Mn uptake does not induce intracellular P deficiency in H. physodes despite that Mn is known to be immobilized with P in H. physodes in intracellular polyphosphate granules and in extracellular encrustations.
Author Keywords: Adenylate energy charge; ATP; Chlorophyll content; Heavy metal tolerance; Mn/Fe ratio; Soredia
Soredia of the lichen Hypogymnia physodes cultivated with Bold's basal medium on agar plates for 8 days exhibited decreasing growth rates along with increasing Mn concentrations above 3 mM. Ca and Mg added separately or in combination, alleviated Mn toxicity. The chlorophyll a and b content of the soredia was reduced under the influence of Mn and was positively correlated with the rate of grown soredia. Trebouxia cells of the soredia grown with excess Mn were smaller than control cells, had reduced chloroplasts and were partly collapsed; fungal hyphae were shortened and strongly swollen. Disintegrated cell walls occurred both in algal and fungal cells. Excess Mn was sequestered in extracellular encrustations together with phosphate as corresponding anion. Intracellularly, Mn was accumulated in polyphosphate granules both in algal and fungal cells. Mn uptake was correlated with significant loss of Na, Mg and Ca, particularly from the mycobiont. Fungal cell walls also lost significant amounts of P. The same damage symptoms occurred in cells of soredia both grown or not, but the former had a higher share of intact cells. Damaged cells of both types of soredia had equally increased Mn concentrations, whereas the total Mn content was higher in not grown soredia than in the grown ones due to the greater amount of damaged cells in the former. The Si-Mn ratio in cell walls of intact Trebouxia cells was significantly higher than in collapsed cells. The experimental evidence of Mn sensitivity of H. physodes soredia corresponds to studies of epiphyte vegetation in montane spruce forests of northern Germany that revealed decreasing cover values of H. physodes with an increasing Mn content of the substrate.
Author Keywords: Chlorophyll content; Heavy metal tolerance; Polyphosphate granules; Soredia; Trebouxia; X-ray microanalysis
Article Outline
1. Introduction
2. Materials and methods
2.1. Soredia growth
2.2. Chlorophyll content of soredia
2.3. Preparation for transmission and scanning electron microscopies
2.4. X-ray microanalysis in the transmission electron microscope
2.5. X-ray microanalysis in the scanning electron microscope
2.6. Statistics
3. Results
3.1. Soredia growth
3.2. Chlorophyll content of soredia
3.3. SEM studies
3.4. TEM studies
4. Discussion
Acknowledgements
References
www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T66-47PP6H3-4&_user=10&_origUdi=B6T66-4FRB7RW-1&_fmt=high&_coverDate=04%2F30%2F2003&_rdoc=1&_orig=article&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=7717e83604ee381dedbef93010f5579e
www.fs.fed.us/wildflowers/interesting/lichens/glossary.shtml
www.sciencedirect.com/science?_ob=ArticleURL&_udi=B7GX0-4K7WJ28-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=46fb80930d8d68f30497f80d76dc5ffc