Safety

• Wear eye goggles
• Avoid all skin contact with the stain
• Gloves
• Take care when using razor blades and mounted needles

Method

1. Cut a very thin section of the stem using a sharp scalpel
   1. thin so light can pass through
2. Transfer each section into a dish containing a toluidine blue O (TBO) stain
3. Rinse off each section with water and mount onto the microscope slide
4. Cover with a coverslip
5. Draw under low power on a microscope

Past Paper Questions

1. Suggest why a stain is used on the stem and root cells
   • The thin sections of the stem and root, do not absorb much light, this are difficult to see under a light microscope
   • The stains absorbs more light, making it easier to see the structures
   • Not all cells are stained to see the differences
2. Explain why it is important not to use too much stain
   • It will be difficult to see anything as the stain absorbs all the light
3. Describe a method for comparing the size of the xylem and the root and stem samples
   1. by using a micrometer slide and an eyepiece graticule.
   2. The graticule is calibrated using a micrometer slide, then the size of each sample can be measured in graticule units and converted to mm to be compared