Comparison of cadmium and copper effect on phenolic metabolism, mineral nutrients and stress-related parameters in Matricaria chamomilla plants

Cadmium and copper uptake and its consequence for activity of selected enzymes of phenolic metabolism, phenolic acids accumulation, quantity of mineral nutrients and stress-related parameters in Matricaria chamomilla plants exposed to 60 μM and 120 μM for 7 days has been studied. Cu content in the above-ground biomass was ca. 10-fold lower compared to Cd and amount of Cd in the methanol-soluble fraction was lower than in the water-soluble fraction. “Intra-root” Cd represented 68% and 63% of total Cd content at 60 μM and 120 μM, but no difference was observed in Cu-exposed roots. Cu excess had more pronounced effect on shikimate dehydrogenase, cinnamyl alcohol dehydrogenase, polyphenol oxidase and ascorbate peroxidase activity mainly in the roots. Among eight detected benzoic acid derivatives and four cinnamic acid derivatives, the latter were preferentially accumulated in response to Cd excess. Content of salicylic acid increased in all variants. Amount of superoxide was elevated in both the rosettes (preferentially by Cu) and roots (preferentially by Cd). Accumulation of Ca and Mg was not affected by excess of metals, while potassium decreased in both the rosettes and roots (Cu caused stronger depletion). Amount of Fe increased in the roots in response to both metals (more expressively in Cu-treated ones). Present study using other metabolic parameters (and supplementing our previous studies) has confirmed higher Cu toxicity for chamomile plants, to support its strong pro-oxidant properties. These observations as complex metabolic responses are discussed.