identifying mitosis in plant cells

• aim 


  To be able to prepare and stain a root tip to observe the stages of mitosis under a microscope.
• • Growth in plants occurs in specific regions calledmeristems
  • The root tip meristem can be used to study mitosis
  • The root tip meristem can be found just behind the protective root cap
  • In the root tip meristem, there is a zone of cell division that contains cells undergoing mitosis
• hydrochloric acid

  • breaks down middle lamaella so the plant lies one cell thick
• staid eg toluidine blue

  • makes the chromosomes visible
  • so you can see which stage of mitosis is occuring
• method

  • Garlic or onion root tips are most commonly used 
  • Prepare a boiling tube of 1M hydrochloric acid and place in a water bath at 60oC for 10 minutes
  • Remove the tips of the roots (about 1cm) and place in the warmed hydrochloric acid for 5 minutes
  • Rinse the tips well in cold water and blot dry with a paper towel 
  • Cut approximately 2mm off the tip and place onto a microscope slide
  • Add a drop of a suitable stain (eg. warm, acetic orcein, which stains chromosomes a deep purple)
• method contiued

  1. The stained root tip is gently squashed on a glass slide using a blunt instrument (eg. the handle of a mounting needle or a cover slip using your fist to gently apply pressure in a rolling motion)
  2. View the slide under the microscope
  3. Cells undergoing mitosis (similar to those in the images below) can be seen and drawn
  4. Annotations can then be added to these drawings to show the different stages of mitosis
• calculating mitotic index

  • The mitotic index is the proportion of cells (in a group of cells or a sample of tissue) that are undergoing mitosis
  • The mitotic index can be calculated using the formula below:

  mitotic index = number of cells with visible chromosomes ÷ total number of cells

  • You can multiply the answer by 100 if you need to give the mitotic index as a percentage