Mutachromosomic chemicals not only cause structrual changes in the chromo somes but also affect the rate of mitosis (Darlington and McLeish 1951, Bowen and Wilson 1954, Rossi 1955, Kihlman 1956, McManus 1959, Davidson 1964, Prasad and Das 1977. These active chemicals belong to divergent groups and vary in their action. Continuous attempts are being made to discover certain general principles of action among these numerous and divergent chemicals. A fruitful method in this field is to study their comparative effects under similar conditions. This paper reports the results of an experiment designed to study the effects of three chemicals of varying concentration and duration on the mitotic behaviour of Atlium cepa Linn. root tips. While the literature on MH and colchicine is large, work with IAA is still scanty. A comparative study of the effects of IAA with MH and col chicine was thus thought to be fruitful.
Materials and methodsThree chemicals namely, maleic hydrazide, MH (an antiauxine), indole-3 acetic acid, IAA (a growth substance) and colchicine (a mitoitc poison) were used for the treatment. The bulbs of Allium cepa Linn. were placed on the mouth of the specimen tubes filled with the aqueous solution of each chemical of 25, 50 and 75 ppm concentrations for 4, 8 and 12 hours and it was ensured that the base and roots of bulbs were dipping in the solution during the treatment. After this treat ment the bulbs were allowed a recovery period of 24 hours in distilled water. The root tips were fixed in 3:1 alcohol-acetic acid and stored in 70per cent alcohol in a refrigerator. For cytological preparations 0.5per cent haematoxylin was used.
ResultsThe effects were studied in two groups namely, the effects on mitotic index and the induction of abnormalities in dividing nuclei.The mitotic index and cell metabolism were greatly affected by all the three chemicals.