Comparative Effects of Colchicine, 8- Hydroxyquinoline and Paradichlorobenzene on the Lengths of Mitotic Chromosomes in Allium cepa L.
*1Ekong, N. J., 2Akpan, G. A., 2Akpabio, K. E. and 1Isa, R. T.
1. Department of Biological Sciences, Federal University Wukari, Taraba State, Nigeria.
2. Department of Botany & Ecological Studies, University of Uyo, Akwa Ibom State, Nigeria.
Abstract: Studies were carried out to assess the comparative effects that 0.5% aqueous solution of colchicine, 0.004M 8-hydroxyquinoline and saturated solution of paradichlorobenzene may have on the lengths of mitotic chromosomes. The somatic chromosomes were studied in root meristems of Allium cepa L. Karyometric analysis of the onion root tips chromosomes revealed a chromosome number 2n = 16. The highest mean haploid chromosomes length of 8.443μm was observed for chromosomes treated with 0.5% colchicine, while 7.168μm and 7.188μm were recorded for chromosomes treated with 0.004M 8-hydroxyquinoline and paradichlorobenzene respectively. Analysis of Variance showed that there were significant differences among the treatments (p<0.05) in the lengths of chromosome 1, 2, 3 and 4 while there were no statistically significant differences (p<0.05) in the lengths of relatively shorter chromosomes (5 – 8) due to the three pre-treatments. Least Significant Difference (LSD) test for chromosomes 1-4 showed that these chromosomes pre-treated with paradichlorobenzene where significantly shorter (p<0.05) than those treated with colchicine, however there were no significant differences between these chromosomes treated with paradichlorobenzene and 8-hydroxyquinoline. Although advantageous, the differential contraction rates due to the three pretreatments, which may have been due to differences in the concentrations of the reagents and position of the sampled cells in the cell cycle, calls for a standardization of measurements of pre-treated chromosomes.
Keywords: Chromosome lengths, mitosis, haploid complement, colchicine, 8-hydroxyquinoline, paradichlorobenzene.
Pages: 125 – 135 | Full PDF Paper