Influence of cadmium on the uptake, tissue accumulation and subcellular distribution of manganese in pea seedlings

Pea (Pisum sativum L. cv. Argona) plants were challenged with Cd in a pure hydroponic system to study the effects on the uptake, tissue accumulation and subcellular distribution of Mn and Fe. This subcellular partitioning was compared to that of maize (Zea mays L. cv. Paolo) plants. In a long-term exposure experiment, Cd was supplied continuously with 0.0 (control), 10 or 50 mu M Cd for 10 days. In a short-term treatment, pea plants were given 50 mu M Cd for 72 h; this was followed by removing Cd from the nutrient solution and investigating the changes in the plants during the period of recovery from Cd toxicity for 96 h. The Relative Growth Increment (RGI) showed that plants treated with 10 mu M Cd suffered moderate stress (70% of the control), whereas those given 50 mu M experienced an strong phytotoxic effect (ca. 30%). In both experiments, Cd accumulated mostly in the roots (90% of the total plant concentration) and almost completely inhibited the uptake of Mn. Only when Cd was removed from the nutrient solution Mn uptake resumed. The relative distribution (%) of Mn between shoots and roots revealed that more Mn was found in shoots as Cd concentration increased in the nutrient solution (from 20% to ca. 50% in Cd-treated plants). Iron concentration and uptake showed less correlation with the Cd treatments. The exposure of pea plants to 10 mu M and 50 mu M Cd caused the severe depletion of Mn in all root subcellular fractions of pea and maize (Zea mays) plants. However, the Mn relative content (%) between subcellular fractions increased in the cell-wall containing fraction, but decreased in the soluble fraction. This effect was also observed in maize plants. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.