(a) What is transpiration?
(b)(i) Name two types of transpiration
(ii) List two factors which affect the rate of transpiration.
(c) Describe the mechanisms of opening and closing of the stomata.
(d) State:
(i) two similarities and (ii) two differences between transpiration and sweating.
Explanation
(a) Transpiration: – This is the loss of water; in vapour form; from the aerial parts/stomata/lentice/stem/leaf of a petal.
(b) (i) Types of transpiration: – stomatal transpiration. – lenticular transpiration – cuticular transpiration
(ii) Factors affecting rates of transpiration: – light intensity/light – temperature – wind – availability of soil water/water -humidity – leaf surface area – leaf structure/thick cuticle – sunken stomata/hairy/spiny – root system (deep/shallow roots)
(c) Mechanism of stomata! opening: –
- when the solute concentration of the guards cells is high.
- water flows from neighboring epidermic/cells into the guard cells.
- by osmosis
- the volume and turgidity of the guard cells increase
- the thin outer walls of the guard cells stretch more than thicker inner walls.
- causing the guard cells/stomata to open
- when the solute concentration is low.
- water flows out of the guard cells by osmosis.
- the volume and turgidity decrease causing the guard cell to become flaccid; and the stomatal pore is closed.
(d) (i) Similarities between transpiration and sweating: –
- Both involve loss of water from the body of the organism.
- both processes result in cooling.
- water is lost through pores.
(ii) Differences:
| Transportation | sweating |
| Occurs in plants through stomata/lenticles | occurs in mammals/skin/through sweat pores |
| Transpiration involves only loss of water | loss of water, salts and nitrogenous waste |
| water is lost in the form of vapour | water is lost in liquid form |
| occurs during the day | occurs both day and night |