Are suspended cells of Viola tricolor L. less tolerant to zinc and lead than seedlings?

The Violaceae family is rich in metallophytes – heavy metal tolerant species with a numerous species in the genus Viola L., especially in Melanium section. In the Southern Poland, on the “old heaps”, Viola tricolor (heartsease) occurs and is classified as a facultative metallophyte – inhabits both contaminated and non-contaminated sites (Słomka et al., 2008). The main goal was estimating the tolerance to Zn and Pb of V. tricolor in the experimental, stable conditions using cells in suspension culture and seedlings. Cell suspension culture was treated with Zn or Pb in concentrations: 200, 500, 1000, 2000 μM (72 h exposure time). Cell viability was estimated using alamarBlue assay. The level of Zn and Pb accumulation in cells was estimated by Atomic Absorption Spectrometry. Cells which survive the highest concentrations of heavy metals were transferred on solidified medium to induce their divisions and callus proliferation. Seedlings tolerance was analyzed using PhytotoxKit test – seeds were treated with aqueous solutions of Zn or Pb in concentrations: 10, 100, 1000 ppm, and then the frequency of germination and root length after 14 days were estimated. Cells of V. tricolor showed high tolerance to Zn and Pb based on their viability after treatments and accumulation of heavy metals. Cells were able to divide after heavy metal stress and produce callus tissue. The toxic effect of heavy metals on seedlings was visible only at concentrations 100 and 1000 ppm. The research has shown that both cells in suspension and seedlings of V. tricolor have a high tolerance to heavy metals.