Calcium effect on number, dimension and activity of nucleoli in cortex cells of pea (Pisum sativum L.) roots after treatment with heavy metals

Abstract Calcium effect on nucleolar activity in the presence of heavy metals (Cd, Cr, Pb) was assessed by determining the variation in number and diameter of nucleoli in cortex cells of Pisum sativum . The ability of cells to incorporate 3 H-uridine and 3 H-lysine into nuclei, nucleoli and cytoplasm was also determined. The presence of metals increased the number of cells with one nucleolus and lowered the number of cells with two but mostly with three nucleoli. Calcium added to chromium diminished the number of cells with one nucleolus increasing those with two nucleoli when this ion was present in cadmium solution. The size of a single nucleolus as well as a total nucleolar dimension in the nucleus of cells both in calcium and those treated with metals underwent reduction as its number increased. Calcium alone and that added to metal solutions enhanced the size of a single nucleolus as well as the total nucleolar dimension. In material treated with heavy metals or after calcium addition the intensity of RNA synthesis in nucleolus and radioactivity of nucleus was positively correlated with the number of nucleoli. Disturbances in this relation within nucleolus and nucleus appeared in the presence of cadmium and lead as well as after calcium addition. No relation between the number of nucleoli and radioactivity of cytoplasm was seen in all experimental series except calcium alone. The lack of positive correlation between the number of nucleoli and radioactivity of nucleoli, nuclei and cytoplasm was also observed after incubation with 3 H-lysine. Exception was nucleolus in the presence of calcium or chromium and lead after calcium addition.