EFFECT OF LEAD ON THE UPTAKE OF NUTRIENTS BY UNICELLULAR ALGAE

From batch growth experiments carried out with the alga Selenastrum ca pricornutum Printz the evolution of uptake of nitrogen and phosphorus with time in the absence and presence of lead 1 x 10(-6) M and at pH 7 and 4 has been considered. The change of pigments (chlorophylls a, b and vegetal carotenoids) with time, as well as the labile and total le ad in the medium and in the alga and the fluorescence compounds releas ed by the alga, have also been analysed. Relationships between phospho rus in the alga and the pigments and lead in the cell, as well as betw een phosphorus and fluorescence compounds exudated by each unit of the unicellular alga, have been examined in order to try to understand th e biochemical mechanism.