What is transpiration? Draw well labelled diagram showing structure of stomatal apparatus in dicotyledons? Mention any three advantages of transpiration.

Answer: Transpiration is the loss of water in the form of water vapour from the aerial parts of a living plant, mainly through the stomata of leaves (also through cuticle and lenticels).

[Diagram to be drawn: surface view of a dicot stomatal apparatus showing two kidney (bean) shaped guard cells enclosing the stomatal pore (aperture); each guard cell with a nucleus, chloroplasts, a thick inner (ventral) wall facing the pore and a thin outer (dorsal) wall; surrounded by subsidiary (accessory) cells and ordinary epidermal cells.]

Advantages of transpiration:

1. It creates the transpiration pull (suction), which is the main force for the ascent of sap (water) in tall plants.
2. It helps in the absorption and upward transport (distribution) of water and dissolved minerals.
3. It has a cooling effect and regulates the temperature of leaves in hot sunlight.
4. It maintains the turgidity of cells and the shape of leaves, and keeps the cell walls moist for gaseous exchange.