Core Practicals Flashcards
(7 cards)
What is the method for CP5: observing mitosis and prepare and stain root tip? (8)
- Add 1 mole of HCL into a bijou jar and place in water bath of 40 degrees for 5 minutes.
- Place growing roots of garlic bulb into the heated acid for 5 minutes.
- Place the roots into a beaker of distilled water and rinse the root tips gently.
- Cut about 2-3mm of root tip of about 8 roots and transfer 2 onto a watch glass.
- Add 1 drop of 1% toluidine blue and stain for exactly 2 minutes.
- Rinse with distilled water until the water runs clear and then place on microscope slide and break apart with mounted needle.
- Add 1 drop of water and remove excess with filter paper and place on cover slip then gently press down to separate the cells.
- View under microscope and identify the stages of mitosis.
What are the 3 evaluation points for CP5 observing mitosis root stain?
- Resolution of microscope
- Human error of counting
- Sufficient time in solutions to enable staining and maceration.
What is the mitotic index calculation?
Number of cells in mitosis (PMAT) ➗ total number of cells counted.
Why is the end of the root tips used to observe mitosis?
Because the end of the root is meristematic meaning the cells are unspecialised to are continuously divided to produce specialised cells so there is lots of mitosis going on.
Why is the garlic bulb roots heated with acid in CP5?
To soften and break up the tissues into individual cells. The cellulose cell walls of plant cells are held together by pectins and so HCL breaks this down.
Why are the root tips stained with toluidine blue?
To stain the chromosomes in each cell to make them visible under the microscope. Toluidine blue used rather than acetic orcein as it is easier and safer.
Why are the root tips squashed in CP5?
To separate the cells in the meristem tissue into individual cells in 1 layer, so that light passes through more easily and easier to identify stages under microscope.
