Role of ploidy in cadmium and nickel uptake by Matricaria chamomilla plants

Cadmium and nickel uptake by diploid and tetraploid chamomile (Matricaria chamomilla L.) cultivars (Novbona and Lutea, respectively) exposed to 60 μM solutions of individual metals over 7 days was studied. Diploid plants accumulated higher amount of Cd in both shoots and roots compared to tetraploid plants while Ni accumulation was ploidy-independent. Cd presence caused higher accumulation of total soluble phenols and flavonoids and higher phenylalanine ammonia-lyase and guaiacol-peroxidase activities in diploid cultivar in comparison with tetraploid but phenolic acids did not show direct correlation with metal accumulation and even decreased in the leaves of Ni-exposed plants. Lignin content was preferentially elevated in the roots of diploid cultivar. Among 17 free amino acids, their sum increased mainly in the leaves of Cd-exposed plants (owing to increase in serine, alanine and proline). Potassium decrease in both cultivars in response to Cd was ploidy-independent and Ca, Mg and Fe accumulation were almost unaffected. It is concluded that Cd accumulation in chamomile may be mediated by the accumulation of phenols but they have no active role in shoot Ni accumulation. Present findings in the context of our previous studies and limited available literature about ploidy effect on metal accumulation are discussed.