1. Experiment No.9
Preparation of temporary mount of leaf epidermis to study the structure of stomata
Measurement of transpiration rate using Ganong’s potometer

2. Temporary mount of stomata
This is not the exact image.
The dark dots represent stomatal pore surrounded by two bean shaped guard cells.
Stomata
Peel can be taken from either surface as Aloe vera is a monocot( equal distribution of stomata)
Place a drop of water on the epidermal peel kept on the slide and visualize under the microscope

3. Transverse section of leaf
Structure of stomata
Stomatal pore acts as a site for diffusion of gases in and out of leaf surface

4. Definitions
Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as from leaves but also from stems and flowers (termed as necessary evil as inevitable to the process of photosynthesis)
It occurs chiefly at the leaves while their stomata are open for the passage of CO2 and O2 during photosynthesis.
Basically of 3 types:
i) Cuticular – Accounts for 10% of water loss through transpiration
ii) Lenticular – Accounts for 1% water loss through transpiration
iii) Stomatal - Accounts for 80-90% water loss through transpiration
There is a difference in distribution of stomata in monocots and dicots.
Monocots(equal no. of stomata on both adaxial and abaxial surfaces)
Dicots(More no. of stomata on abaxial surface(lower).

5. Uses of Transpiration Provides a cooling effect to the plant
Enables mass flow of nutrients and minerals along with water to shoots and leaves from roots

6. Factors affecting the rate of transpiration
No. of leaves
No. of stomata
Temperature
Humidity
Intensity of sunlight
Wind
Water supply to the plant

7. Measurement of the rate of transpiration
Equipment used: Potometer(we would be using Ganong’s potometer)
A potometer( transpirometer) is a device used for measuring the rate of water uptake of a leafy shoot.

8. Points to remember…
Ganong’s potometer only measures the rate of water uptake ,it cannot give an idea of actual transpiration rate
Alterations to light intensity, wind and humidity should be avoided
Immediately after the twig it cut, immerse it under water to prevent entry of air to xylem vessels
Twig may not be active for long time.
Correct sealing by wax should be done to avoid any leakage.

9. Calculations