Influence of additional Cd and Cu supply on Zn toxicity in compost-peat substrates

Since compost-peat substrates may be contaminated with more than one heavy metal, this study was carried out to determine the influence of additional Cd and/or Cu supply on Zn toxicity For this, Petunia X hybrida were grown in compost-pear substrates with Cd (1.4 mg kg(-1)), Cu (87 mg kg(-1)), and Zn (365 mg kg(-1)), Zn (365 mg kg(-1)) (all in aqua regia) supply in different combinations. The level of chlorosis and the dry matter yield were not affected by the combined application of Cd, Cu, and Zn compared to a single application. Plant Zn contents were reduced when Zn was given in combination with Cd and/or Cu. Plant Cu contents increased under Zn addition, whereas plant Cd contents remained unaffected by mixed heavy metal supply. The phytoavailable Zn, which was determined with Zn supply alone is valid for the case of combined Zn, Cd, and Cu supply, because chlorosis was not increased, plant Zn contents decreased, and the amount of CaCl2 extractable Zn was not altered under Cd and/or Cu addition.