core practical 6: observing the stages of mitosis

what are meristems

where growth in plants occur

• The root tip meristem can be found just behind the protective root cap

how root tips can be studied

• temporary slides can be prepared using the squash technique (root tips are stained and then gently squashed, spreading the cells out into a thin sheet and allowing individual cells undergoing mitosis to be clearly seen)

apapratus

• Roots of onion or garlic

• Microscope slide

• Cover skip

• 1 M hydrochloric acid

• Stain (acetic orcein, toluidine blue for example)

• Paper towel

• Scalpel blade

• Cutting tile

• Water bath at 60^oC

• Boiling tube

• Optical microscope

method fro observing root cells

1. grow roots on in control and one in soluiton being tested

2. Prepare a boiling tube of 1M hydrochloric acid and place in a water bath at 60^oC for 10 minutes

3. Remove the tips of the roots (about 1cm) and place in the warmed hydrochloric acid for 5 minutes/

4. Rinse the tips well in cold water using a pipette and blot dry with a paper towel 

5. Cut approximately 2mm off the tip and place onto a microscope slide

6. Add a drop of a suitable stain (eg. warm, acetic orcein, which stains chromosomes a deep purple, toluidine blue)

7. then root tip placed on a microscope slide and macerated / teased / described} and squashed

8. use of high power (on a microscope)

wearing gloves / goggles

why root tups placed in acetic orcin in a water bath at 55 degrees celcius and left for five minutes?

to stain/dye/colour the chromosomes

why a coverslip was placed over the root tips and squashed gently?

to spread/ separate the cells out

the slide was then viewed first using low power and then high power of a microscope why?

to locate and then magnify the cells

describe procedure to investigate the effect of pH on mitotic index?

• use range of pH solutions

• in which plants grown

• several root tips from each pH

• take cells from same part of root tips

• count num of cells undergoing mitosis and total num of cells

• in several fields of view