| Summary: | Lead uptake by young cucumber (Couches satires L.) seedlings growing in 10-4 and 10-3 M PbCl2 solution caused δ-aminolevulinic acid synthesis inhibition, reduced the activity of δ-aminolevulinic acid dehydratase and the chlorophyll centent in the cotyledons. Lead mainly accumulated in the roots (ca 93-96% of Pb uptake) and hypocotyls (ca 4-6%), whereas only trace Pb amounts were found in the cotyledons when 10-3 M solution was used. It is supposed that one of the causes of the reduction of chlorophyll synthesis by lead is its influence on tissue hydration which diminished to about 50 per cent as compared with the control. The direct effect of lead on the examined steps of chlorophyll synthesis cannot, however, be ruled out.
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