High specificity in response of pea mutant SGECdt to toxic metals: Growth and element composition

Abstract The present report aimed to better understand the mechanisms of plant co-tolerance to various toxic metals, and relationships between metal tolerance and metal accumulation. The pea ( Pisum sativum L.) line SGE and its mutant SGECd t , having increased tolerance to and accumulation of Cd, but decreased tolerance to and accumulation of Hg, were cultivated in hydroponics at a range of toxic concentrations of heavy metals (Cd, Co, Cr, Hg, La, Ni, Pb and Zn), as well as Al, Fe, Mn, NaCl and H + ions. The SGECd t mutant showed increased tolerance to Co (increased root biomass at 12 and 25 μM Co and shoot biomass at 25, 50 and 100 μM Co), but similar root and shoot Co contents as SGE. No significant differences between SGE and SGECd t in biomass response to other metals and low pH were detected. However at particular metal concentrations, SGECd t tended to (Student's t test, P t . Generally, metal toxicity decreased macro- and micro-element (nutrient) concentrations in plants, however opposite effects were also observed particularly on Hg-treated plants. SGECd t had increased root Ca, Fe, Mg, Mn and S content and shoot B, Ca, Mg, Mn, Na and Zn content in Cd-treated plants. In the presence of toxic Hg the mutant contained less root and shoot Ca, K, Mg and S, but had increased root Co, Cr and Cu contents. Genotypic differences in individual nutrient elements were also observed following Ag, Al, La, Mn, Ni or Zn treatment. Taken together, the results indicate high specificity in phenotypic responses of SGECd t exposed to toxic metals and that the mutation might affect some regulatory genes, which could modulate nutrient (particularly Ca) homeostasis and regulation of ion transporters.