Impact of spiked concentrations of Cd, Pb, As and Zn in growth medium on elemental uptake of Nasturtium officinale (Watercress)

abstract

This study is aimed at investigating the impact of water quality on the uptake and distribution of three non-essential and toxic elements, namely, As, Cd and Pb in the watercress plant to assess for metal toxicity. The plant was hydroponically cultivated under greenhouse conditions, with the growth medium being spiked with varying concentrations of As, Cd and Pb. Plants that were harvested weekly for elemental analysis showed physiological and morphological symptoms of toxicity on exposure to high concentrations of Cd and Pb. Plants exposed to high concentrations of As did not survive and the threshold for As uptake in watercress was established at 5 ppm. Translocation factors were low in all cases as the toxic elements accumulated more in the roots of the plant than the edible leaves. The impact of Zn on the uptake of toxic elements was also evaluated and Zn was found to have an antagonistic effect on uptake of both Cd and Pb with no notable effect on uptake of As. The findings indicate that phytotoxicity or death of the watercress plant would prevent it from being a route of human exposure to high concentrations of As, Cd and Pb in the environment.

Keywords:

• Watercress
• toxic metals
• hydroponics
• antagonism
• synergism
• toxicity
• elemental uptake
• zinc
• cadmium
• lead
• arsenic

Funding

The authors are thankful to the University of KwaZulu-Natal and the National Research Foundation (NRF) for financial support and research facilities.