Chemically induced alterations of the nuclear cycle and chromosomes in root meristem cells of maize

Abstract

Cycloheximide, chloramphenicol, and mitomycin C (MC) appear to act mainly on the G2 and S phases, resulting in lengthening the duration of the nuclear cycle in the S and G2 periods. Cycloheximide and chloramphenicol did not affect the duration of G1 at 25°C. However, at 30°C, G1 was extended considerably by both chemicals. No effect on mitosis was noted by these chemical additives; therefore, the prolongation of the duration of nuclear cycle was mainly because of a prolonged interphase. There was a significant reduction in mitotic indices after treatment in comparison with the control values. The results indicate that the mitotic inhibition was mainly in the G2 and S periods. MC produced a high frequency of chromosomal aberrations, mostly isochromatid breaks, chromatid breaks, and exchanges, and it was concluded that this drug is very active as a chromosome-breaking agent in Zea mays. The induced aberrations are not equally distributed among the chromosomes or within a single chromosome. The high frequency of damage occurred in the regions of the nucleolar constriction, centromeres, and heterochromatic areas. Mutagenicity of MC was also studied and the results indicated that it induced chlorophyll, waxy, and shrunken mutations in Zea mays.