Accumulation of Nickel by Excluder Thlaspi arvense and Hyperaccumulator Noccaea caerulescens upon Short-Term and Long-Term Exposure

The ability to accumulate nickel (Ni) was compared in hyperaccumulator Noccaea сaerulescens F.K. Mey and excluder Thlaspi arvense L. after a short-term (1, 2, or 3 days) and long-term (8 weeks) exposure. T. arvense and four accessions of N. сaerulescens (La Calamine (LC), Saint Félix de Palliéres (SF), Monte Prinzera (MP), and Lellingen (LE)) were grown on a half-strength Hoagland`s solution in the presence of 25 µM Ni(NO₃)₂ (N. сaerulescens and T. arvense) and 250 µM Ni(NO₃)₂ (N. сaerulescens; T. arvense for only 1–3 days). Metal content in the roots and shoots was determined by atomic absorption spectroscopy. The Ni content per unit mass in the roots and shoots of N. сaerulescens in most cases did not differ significantly after the short-term incubation. At 25 µM Ni in the nutrient solution, its content in the roots of LC plants after 2–3 days of incubation was lower than in T. arvense, whereas Ni content in the shoots of these plants was similar. In the plants of other accessions of N. сaerulescens, Ni content in the roots and shoots in most cases was higher than in T. arvense. At 250 µM Ni, the differences in metal content in the roots were insignificant, and its content in the shoots in all the accessions of the hyperaccumulator was much higher than in the excluder. The Ni translocation factor was higher in N. сaerulescens than in T. arvense and exceeded unity only in the plants of MP accession. After the long-term exposure, the Ni translocation factor was higher than 1 in plants of all accessions of N. сaerulescens and decreased in the following order: MP ≈ LC > LE ≥ SF; in T. arvense, it did not exceed 0.3. Upon both long-term and short-term exposure, the ability to accumulate Ni by N. сaerulescens plants of different accessions generally increased in the following order: LC < SF < LE < MP. However, minor changes were observed depending on the duration of exposure and Ni concentration in the medium. Thus, considerable differences in the ability to accumulate Ni among the plants of different accessions of hyperaccumulator N. сaerulescens became apparent as early as during the first days of exposure to Ni and hardly depended on the duration of incubation or metal concentration in the medium. The obtained data confirm the assumption about a constitutive or genetically predetermined ability of plants of different N. сaerulescens accessions to accumulate Ni.