Is the Binding Pattern of Zinc(II) Equal in Different Bryophyte Species?

Bryophytes are usually taken as good bioindicators. However, they represent a large group of terrestrial plants and they express an enormous range of peculiarities within the plant kingdom. With the aim to search for a common pattern of zinc binding, we established axenical in vitro cultures of a dozen bryophyte species that include hornworts, thallose, and leafy liverworts, as well as acrocarp and pleurocarp mosses. The species were grown free of contaminants for many years prior to the application of different treatments, i.e. offering Zn(II) from solid and liquid media and in combination with different anions. The localization and binding of zinc was detected by confocal microscopy using the zinc-specific dye FluoZin™-3. In one of the species, Hypnum cupressiforme (which is widely used for atmospheric heavy metal deposition studies in biomonitoring), semi-quantitative analyses of zinc were performed by energy dispersive X-ray microspectrometry (EDX) in a scanning electron microscope. The results suggest no common pattern of Zn(II) binding in different bryophyte species. Instead, the binding pattern seems to be species specific. Zinc is located in certain areas or cellular compartments, as clearly shown by the EDX measurements in H. cupressiforme.