Calcium has protective impact on cadmium-induced toxicity in lichens

Mercury Content and Amelioration of Its Toxicity by Nitric Oxide in Lichens

“…The same ROS stimulation has been observed in the green alga exposed to 100 µM Hg, but not Pb [ 14 ], or in plant roots exposed to Hg [ 30 ], providing evidence that Hg is more toxic than many other common metallic contaminants. It is also known that oxidative stress markers differ in lichens treated by metals in relation to morphology and even depleted H 2 O 2 content was observed after spray application of Cd [ 31 ], while immersion in Cd-enriched solutions led to enhanced ROS or H 2 O 2 formation detected by fluorescence microscopy and standard spectrophotometry [ 18 ].…”

“…Their considerably lower accumulation in Hg-exposed thalli ( Figure 3 ) may be a reason for Hg-enhanced ROS formation ( Figure 2 ); the same was observed in algae, also exposed to 100 µM Hg but not to Pb [ 14 ]. Higher toxicity of Hg may also be deduced from the fact that 100 µM Cd in the similar fruticose lichen Ramalina stimulated accumulation of AsA [ 24 ], while the foliose lichen Hypogymnia responded to 100 µM Cd excess by depleting AsA and thiols [ 18 ]. The negative effect of Hg is concentration- and species-dependent, and no changes in AsA and/or thiols were observed in vascular species Medicago treated with 30 µM Hg for 24 h [ 2 ] or in Arabidopsis leaves treated with 10 µM Hg for 72 h [ 22 ]; but even increased accumulation was observed in the cyanobacterium Nostoc , exposed to 0.5–3 µM Hg for 72 h [ 1 ] or in rice roots exposed to 100 µM Hg, as we also used [ 3 ].…”

“…Phenolic metabolites (soluble phenols) remained unaffected by SNP application alone or in combination with Hg, as previously observed in the green microalga [ 16 ], but were depleted by more than 50% due to Hg excess ( Figure 3 ). This is a further indication of higher toxicity of Hg alone, as, e.g., 100 µM Cd had no effect on phenols in the foliose lichen Hypogymnia [ 18 ], and may also indicate specific interaction of Hg with specific lichen metabolites, many of which are (chemically) phenolic in nature. Amino acids, as a basic part of proteins, are often affected by excess metals in plants and lichens and were strongly depleted by the excess Hg ( Figure 3 ), with similar depletion also evoked by the 100 µM Cd excess in Hypogymnia [ 18 ].…”

“…This is a further indication of higher toxicity of Hg alone, as, e.g., 100 µM Cd had no effect on phenols in the foliose lichen Hypogymnia [ 18 ], and may also indicate specific interaction of Hg with specific lichen metabolites, many of which are (chemically) phenolic in nature. Amino acids, as a basic part of proteins, are often affected by excess metals in plants and lichens and were strongly depleted by the excess Hg ( Figure 3 ), with similar depletion also evoked by the 100 µM Cd excess in Hypogymnia [ 18 ]. In the green microalga, proteins were strongly depleted by 100 µM Hg excess [ 14 ].…”

“…To cope with ROS overproduction, all cells use mainly non-enzymatic antioxidant ascorbic acid and thiol metabolites, and its significance under metal excess is also known in lichens [ 17 ]. Phenolic metabolites as additional antioxidants and amino acids as basic metabolic/enzymatic components are also affected by the excess of metals in lichens [ 18 ], but the impact of Hg and regulation of metal-induced ROS formation is not well understood.…”