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Microscopy of root tip mitosis

In plants, cell division by mitosis takes place in specific tissues, called meristems, that are found at the growing root and shoot tips and in the cambium between the xylem and phloem of the vascular bundle. The cells in the meristems are undifferentiated. In this practical, students will prepare and observe dividing cells from the meristems of actively growing garlic root tips.

In this practical protocol, toluidine blue is used to stain the DNA in the meristem cells, instead of the more traditionally-used acetic orcein. This is because:

  • Toluidine blue has been found to produce a level of contrast within the cells that allows chromosomes to be clearly seen

  • The protocol developed here, using toluidine blue, is a simpler process than protocols involving acetic orcein

  • The use of toluidine blue in a school laboratory is less hazardous than the use of acetic orcein

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