Abstract (eng)
Copper, although an essential micronutrient, is generally toxic in large quantities. In mosses, the exclusion mechanisms known from higher plants can not be applied analogously due to the different morphology. Nevertheless, there are some genres that are apparently equipped to tolerate this heavy metal stress and naturally occur on copper-containing substrate - eg. Former mining heaps.
In this work, the effects of copper on morphology, Chlorophyll a/b ratio and oxidative stress levels were examined in the copper-sensitive species Aphanoreghma patens and the two copper-tolerant species Mielichhoferia elongata and Pohlia drummondii. The mosses were growing on medium supplemented with 0.1 mM CuCl2, 0.1 mM CuSO4, 0.1 mM or 10 mM CuEDTA. Growth height, copper uptake and oxidative stress were examined after six weeks treatment with copper. Cell size and Chlorophyll a/b ratio were additionally measured in the first week of copper treatment and after six weeks of regeneration on copper-free medium.
A. patens showed reduced growth as well as increased staining by oxygen radicals in the CuCl2 and CuSO4 treatments; there was also highly enriched copper found along the stems. In the two adapted mosses M. elongata and P. drummondii the copper showed, however, a beneficial effect for plant height. In addition, the copper enrichments were found only in the base of the stems. In M. elongata a much faster decrease in the amount of copper along the stems was measured than in P. drummondii.
In treatments with CuEDTA, A. patens had larger plants than in the copper-free medium. Despite the high enrichment of copper, which was found in all moss-species, there was less oxidative stress observeable. M. elongata also showed large plants, but it had much more stress and also relatively more chlorophyll b than in the control. Common in all species was a strong increase in cellsize and a strong shift to more chlorophyll a in the regeneration after CuEDTA treatments.
It could be shown that the copper-tolerant species M. elongata and P. drummondii were better adapted to the CuCl2 and CuSO4 than the copper-sensitive species A. patens. In CuEDTA treatments, M. elongata responded more negatively to CuEDTA than A. patens.