The duckweed Lemna minor was cultivated under laboratory conditions with the amount of incident light as limiting growth factor. The fronds were found to double every 3 days under the highest radiation intensity. The plants were exposed to Cu and Cr(III) solutions of 0.25 and 1.0 mg ℓ−1 during 10 days. The plants needed to adapt for app. 8 days before attaining maximal, steady state removal. Cr(III) was removed more efficiently from the solution (75-100% in terms of concentration or load reduction) than Cu (35-40%), the higher efficiencies pertaining to the more dilute solutions. Uptake rates were 80-333 and 250-667 mg d−1 m−2 for Cu and Cr(III), respectively. The plants accumulated 1-2 g metal kg−1 plant (dry weight) when exposed to the high concentration. Cu seemed toxic at 1.0 mg ℓ−1, resulting in plant mortality after 8 days.

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