Pre-Treatment and fixation
A pre-treatment chemical is used to increase the proportion of metaphases in
the root tip meristem by inhibiting the formation of the spindle (12). The root tips were
treated in either 1-bromonapthalene (MBN saturated aqueous solution, at 4°C, for 24
hours) or 8-hydroxyquinolene (OQ aqueous solution, 0.002-0.02M, at 13°C, for 5-7
hours). Pre-treatment is very important since the success rate of staining depends
directly on the good metaphases rather than the dyes used in the staining stage (13).
Fixation is necessary to kill the material rapidly in such a way that the internal
structures are preserved in a life-like form. In this study, the root tips were treated in
Farmer’s fluid for 24 hours. Dyer (12) suggests a fixation period of 5 minutes to ethanol and 1 part glacial acetic acid.