Answer reviewed 23/01/2023
There are a number of different stains available that are suitable for use in the science classroom, including toluidine blue, methylene blue, and aceto-orcein.
Toluidine blue is a very effective stain for the visualisation of mitosis in root tips of onions or garlic.
Science ASSIST recommends Toluidine blue as a stain, as it is cheaper and less hazardous than aceto-orcein stain. It has been found to produce a level of contrast within the cells that will allow your students to easily see the chromosomes. It also has a simpler process than Aceto-orcein.
You can find a full procedure for preparing the stain and completing a root tip mitosis practical at STEM Learning.
Aceto-orcein stain is an effective procedure for the visualisation of mitosis in root tips of onions or garlic.
Orcein can be purchased in solid form, the solution is prepared with acetic acid. A full method for stain preparation and procedure can be found at Mitosis in Growing Root Tips.
Alternatively, Aceto-orcein can be purchased as a 1% solution to be used undiluted. Each student group requires one drop of stain, so the prepared stain is cost effective. The cost of the stain and delivery charges vary between suppliers, and is moderately priced.
Aceto-orcein solution is suitable for laboratory use for students in Years 11 and 12.
Methylene blue will also show mitosis in root tips. It is easy to prepare, and the staining procedure is similar to Toluidine blue
Flinn Scientific has a good procedure for you to follow here.
Science ASSIST recommends you consult the relevant Safety Data Sheet first and our List of recommended chemicals for science in Australian schools to ascertain the suitability of these stains for your staff and students.
‘Mitosis in growing root tips’. Gene Technology Access Centre website. https://gtac.edu.au/wp-content/uploads/2016/01/Mitosis_Roottips_LabPreparation.pdf (Accessed 18 Jan 2023)
‘Aceto-orcein 1% SI1' product description. Chem Supply Australia. https://shop.chemsupply.com.au/documents/AL025.pdf (Link Updated August 2022)
Science ASSIST. 2016. List of recommended chemicals for science in Australian schools. https://assist.asta.edu.au/resource/4669/list-recommended-chemicals-science-australian-schools-2021
STEM Learning. N.d. Microscopy of root tip mitosis. Retrieved (09 January 2023) from STEM Learning website: https://www.stem.org.uk/resources/elibrary/resource/150333/microscopy-root-tip-mitosis (Login with a free account)
Making Mitosis Slides (with methylene blue stain solution). Retrieved (23 January 2023) from Flinn Scientific website: https://www.flinnsci.com/making-mitosis-slides/dc10945/