Effects of Zinc on Metallicolous and Non-Metallicolous Populations of Noccaea caerulescens

The aim of this study was to evaluate whether intraspecific differences in zinc (Zn) tolerance and accumulation in the hyperaccumulator <i>Noccaea caerulescens</i> are linked to Zn-induced changes in transpiration and mineral composition. At 500 µM Zn in the nutrient solution, a decrease in the root and shoot biomass, the water content in roots, and the contents of photosynthetic pigments in shoots was observed only in the non-metallicolous population Wilwerwiltz, whereas in the calamine population Prayon, root growth was stimulated. Zinc-induced impairment of mineral nutrition was greater in Wilwerwiltz than in Prayon, which determined the manifestation of Zn toxicity in Wilwerwiltz. The absence of signs of Zn toxicity and the stimulation of root growth in Prayon may be due to lower Zn accumulation in Prayon than in Wilwerwiltz, as well as more effective mechanisms of Zn detoxification. The higher Zn content in the shoots and, in particular, in the water-storage cells of the leaf epidermis in Wilwerwiltz compared to Prayon may be partly due to the higher transpiration rate in Wilwerwiltz, at least at 500 µM Zn. These findings suggest that the metallicolous population maintains better control over Zn accumulation, which may be a part of the adaptive response to Zn-enriched media.