Seed germination and seedling growth of Ailanthus altissima, Acer negundo, Pinus silvestris, and Picea abies in elevated concentrations of Zn, Pb and Cd under laboratory conditions

Abstract

Phytoremediation and phytostabilisation of abandon open miming sites is very important process for rehabilitation of land and watercourses to an acceptable standard. Seed germination and seedling establishment in post-mining sites is of great importance for early succession and restoration patterns. Several of early colonizers are tree species, but they could be very important elements of early successions and influence dynamic of early revegetation in disturbed areas. Spontaneous colonization of mining spoils is difficult due to extremely difficult condition such as extremely low or high pH, mineral soil, low water capacity and nutrient deficiency. Besides this, high concentration and solubility of toxic metals in mining areas could be the most limiting factor for plant establishment. We analyzed parameters of seed germination and seedling growth of early successional tree species (two broad leaf and two pine species species against): Ailanthus altissima, Acer negundo, Pinus silvestris, Picea abies in several experimental systems with three different concentration of toxic metals (Pb, Cd, Zn) to assess influence of metal toxicity in early phase of plant development. Lead in applied concentrations (25, 50 and 100 mu M) did not affect significantly the seed germination percentage in Ailanthus altissima and Acer negundo while cadmium in highest concentrations (100 mu M) caused reduction of the germination percentage, germination index and vigor index in both species. Analysis of the parameters of early seedling development indicates the most pronounced toxic effects of cadmium. In Ailanthus altissima Zn treatments caused significant inhibition of shoot growth and repress development of assimilating organs in concentrations of 25, 100 and 250 mu M. In concentration of 25 mu M Zn caused an inhibition of the root growth. The spruce and Scot pine seeds which were developed on substrates with addition of heavy metals solutions showed significant tolerance to presence of all metals, but percentage of germinating seeds depended on the type of metal and its concentration. The seed of P. abies demonstrated higher tolerance to presence of heavy metals in lower concentrations, then seed of Pinus sylvestris and germinated in all variants. In the conditions of highest concentrations, the seeds of both species did not sprout regardless of the type of metal. The P. abies seedlings were very tolerant to the presence of all metals. The highest concentrations of cadmium had a significant influence on the decrease of the number of the seedlings which survived, as well as on the decrease of biomass in comparison to lead. Zinc had the least adverse effect on the growth and survival of seedlings. P. sylvestris seedlings did not exhibit the same tolerance for the presence of heavy metals.