Physiological mechanisms of adaptation of Dianthus carthusianorum L. to growth on a Zn-Pb waste deposit - the case of chronic multi-metal and acute Zn stress

Abstract

Aims: This study investigates the response of metallicolous (M) and nonmetallicolous (NM) ecotypes of Dianthus carthusianorum L. to chronic multi-metal and acute Zn stress. Methods: Plants were cultivated on the Zn-Pb waste heap substrate and under Zn excess in hydroponics. Growth parameters as well as accumulation of organic acids and thiol peptides were determined as a function of metal accumulation. Results: When grown on the metalliferous substrate, the M plants showed less phytotoxicity symptoms, lower foliar metal (Zn, Pb, Cd) accumulation, higher malate and citrate but lower glutathione content than the NM plants. When exposed to Zn excess in hydroponics, the M ecotype was also more tolerant but accumulated more Zn in comparison with the NM ecotype, accompanied by greater malate and citrate concentrations in the shoots, which were however not affected by increasing Zn doses. No phytochelatins were detected under any experimental conditions. Conclusions: Both constitutive and adaptive tolerance was found in D. carthusianorum. Under chronic metal stress, enhanced tolerance results from restricted metal uptake to the shoots and probably from detoxification by organic acids; however, under acute Zn stress it is not related to diminished metal uptake or organic acids. Glutathione and phytochelatins are not implicated in adaptive metal tolerance.