Lead distribution in corn seedlings (Zea mays L.) and its effect on growth and the concentrations of potassium and calcium
2002
Malkowski, E. | Kita, A. | Galas, W. | Karcz, W. | Kuperberg, J.M.
It was observed that dry weight yield is not a sensitive parameter with which to assess lead toxicity to plants. Elongation growth of corn seedling roots was more sensitive to lead than shoot growth and was inhibited by all concentrations tested (10-5, 10-4, and 10-3 M). It was positively correlated with potassium concentration and negatively correlated with lead concentration in the roots. Negative correlation also was observed between lead concentration and potassium concentration in roots. It is postulated that inhibition of corn root growth is connected with potassium leakage from root cells. The toxic action of lead on corn seedling mesocotyl and coleoptile growth was not correlated with potassium concentration in plant tissue and correlation between growth and lead concentration was low. In seedlings treated with 10-4 and 10-3 M lead the growth of mesocotyl and coleoptile was affected similarly, although the concentration of lead was threefold higher in mesocotyl tissue than in coleoptile tissue. It is proposed that depression of corn seedlings shoot growth is not an effect of potassium leakage or lead accumulation but of an unknown signal induced in roots, as a response to exposure to lead, which is transmitted to shoots. The positive correlation between lead and calcium concentrations found in seedling roots might be connected with high constitutional tolerance of corn to lead. Since the first 8 mm of an apical root accounts for 50% of the lead accumulated by the whole root, it is postulated that rhizofiltration of lead contaminated waters should be more efficient when plant species with highly branched root systems are used.
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