RP 2 - Calculating Mitotic Index

• Plant cells undergo mitosis at shoot and root tips in areas called meristems.
• Cells in the meristems are totipotent and retain the ability to differentiate.
• The mitotic index of a sample is the ratio of cells undergoing mitosis to the total number of cells in a sample.
• To find the mitotic index, cells from the meristem must be viewed under an optical microscope.
• Equipment for the preparation of stained squashes of cells from plant root tips includes an optical microscope, microscope slides and cover slips, water bath, hydrochloric acid, toluidine blue O stain, distilled water, scalpel, forceps, 100 ml beaker, root tip.
• To prepare stained squashes of cells from plant root tips, heat 1 mol dm -3 HCl at 60 °C in a water bath, cut a small sample of the root tip using a scalpel, transfer root tip to HCl and incubate for 5 minutes, remove from HCl and wash sample in cold distilled water, remove the very tip using a scalpel, place tip on a microscope slide and add a few drops of stain (e.g. toluidine blue O), lower the cover slip down carefully onto the slide, place under a microscope and set the objective lens on the lowest magnification, use the coarse adjustment knob to move the lens down to just above the slid
• Risk assessment for the preparation of stained squashes of cells from plant root tips includes hazards such as hydrochloric acid which may cause harm/irritation to eyes or in cuts, toluidine blue O stain which may cause harm/irritation to eyes or in cuts, and cuts from a sharp object which can be prevented by using forceps to hold the sample while cutting and keeping away from the edge of the desk.
• If a cut does occur, it should be elevated, pressure should be applied, and medical assistance should be sought.