Estimation of DNA Synthesis Period (s) by Different Methods in Root Meristem Cells of Zea mays L.: Inhibition of DNA Synthesis by Several Antimetabolites

Abstract

The duration of DNA Synthesis period (S) is estimated by three different methods by autoradiography with ³H-TdR in Zea mays L. root meristem cells. It is concluded that the three methods yielded similar results. It is presumed that the accuracy of estimating S period by any of three methods depends on the sample size and the mechanics of plotting the curve. The duration of DNA Synthesis was prolonged in roots treated with cycloheximide, chloramphenicol, mitomycin C (MC) or hydroxylamine sulphate (HAS). The incorporation of ³H-TdR) after treatment with MC and HAS was also observed. It was found that MC reduces the incorporation of the radioactive precursor (₃H-TdR) into DNA, not only during the time of treatment, but also after the treatment. HAS was also found to inhibit the incorporation of ³H-TdR into DNA but the incorporation increased soon after the removal from HAS. The action of HAS on inhibition of DNA Synthesis is different from that of MC. Furthermore, it was found that the effect of HAS on nhibition of DNA Synthesis is easily reversible.