Required Practical 2 - Preparation of Stained Root Tip Squash Flashcards
Suggest why an optical microscope is used
Has a high enough magnification to view chromosomes
Suggest why root tip is gently squashed onto microscope slide
- gently to avoid damage to cells
- thin layer of cells to take up better stain and for light to penetrate easily to clear observation
Suggest why root tip is soaked in hydrochloric acid
- necessary to dissolve middle lamella
- cells spread easily for clear observations
Suggest why root tip is heat treated
Allows chromosomes to take a deeper stain
Suggest the purpose of a stain and give an example
- Toluidene/Orcein
- easily identify chromosomes with DNA due to contrast
Suggest why a root tip is used to observe mitosis
- contain meristem tissue
- cells undergo regular mitosis
Suggest why the root tip of onion, garlic or shallot is usually used
- easy to grow in large numbers
- can take up stain and be flattened onto slide
Suggest why it is important the coverslip is not moved side to side
- avoid breaking chromosomes
- avoid overlapping/rolling cells
Suggest why it is sensible to mount both sides of root tip
- easy to confuse ends
- cells behind the meristem elongate and are easier to differentiate under the microscope
Describe how you could make a temporary mount of a piece of plant tissue to observe starch grains using an optical microscope
- cut a thin slice of plant tissue
- place on a glass side using forceps and add a drop of water
- add a few drops of iodine (or other appropriate stain)
- lower coverslip using a mounting needle