Root Tip Squash (AS Biology Unit 2 Topic 3 Edexcel)

"Describe the stages of mitosis and how to prepare and stain a root tip squash in order to observe them practically." spec point 2.3.7

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Root Tip Preparation

  • Cut 1cm of a root tip of a growing plant (e.g. onion) 
    => this is because the root tips are the area where unspecialised cells are going through mitosis, which is what we want to observe
  • Place 2cm(3) of HCl into a 60ºC waterbath until it reaches the temperature 
  • Place into a testube of 2cm(3) of HCl for 5 minutes 
    => this breaks down the middle lamella between the plant cells
    => allows more of the stain to be absorbed making observation of the cells easier
  • Remove and place into cold distilled water for 5 minutes
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Observation

  • Place root tip onto a microscope slide
    => this is used to observe the root tip on
  • Using a glass rod, smooth out, or "squash", the root tip cell 
    => too thick will make it hard to differenciate cells above and below
    => too thin may cause it to break
  • Put a drop of a dye, e.g. acetic orecin on the root tip and leave for 2 minutes
    => this is to allow time for the dye to run through the cells
  • Place cover slide on top of the root tip and, using filter paper, blot any excess dye that runs from the cover slide
  • When observing under the microscope you should be able to view the different stages of mitosis
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