Calcium influence on the dry mass content and surface area of nuclei and cytoplasm during differentiation of cortex cells in pea (Pisum sativum L.) roots treated with heavy metals

The effect of Ca addition to Cd, Cr and Pb solutions on the nuclear and cytoplasmic dry mass content and its concentration as well as on these organelles dimensions were studied in cortex cells of pea roots. Ca alone, at the concentration 10(-8)M brought about a decrease (in comparison to water) in the dry mass content of nuclei and its concentration, but the increment was almost twice in the dry mass content of cytoplasm; however, it has no significant effect on its concentration. Ca ions addition does not change the surface area of nuclei except the 1st and 5th mm segments but causes a doubling of the area occupied by cytoplasm. In response to Ca addition to Cd or Cr solutions a further diminution of nuclear dry mass content takes place. Only in the case of Pb nuclear dry mass increases in the 7th mm or is similar in remaining root segments. The diminution of nuclear dry mass content due to Ca presence in metal solutions is accompanied by a lowering in its concentration, although in the presence of Cd and Pb the diminution is not significant. Ca ions addition results in an increase in cytoplasmic dry mass content. No such regularities were observed in the 1st (Cd, Pb) and 3rd (Cr) root segments. In response to Ca ions the concentration of cytoplasmic dry mass content increased insignificantly in differentiation zone and underwent reducation in the meristematic zone--in the 1st mm (Cr) and 3rd (Cd). After Ca addition to studied metal solutions the decrease in nuclear dimensions was visible only in Cd or Pb treated cells in the 3rd and 7th or in the 1st mm, respectively. An increase in nuclear size occurred only in Cr treated cells in the 7th mm. Enrichment of heavy metals with Ca caused the marked enlargement in cytoplasmic area in differentiation zone but the increment in it in meristematic zone was observed only in Cd (1st, 3rd) and Cr (1st) treated cells.