Transpiration
- ICSE Class 10, Unit 2 Plant Physiology
Transpiration is the loss of water as water vapour from the parts of a plant above the ground, mainly through the stomata of its leaves.
Water vapour leaves a plant in three ways. Through the stomata of leaves, through the waxy cuticle, and through lenticels, small pores on woody stems. As water leaves the leaves, it pulls more water up from the roots.
Guttation is different. There, water leaves as liquid drops from the edges or tips of leaves, through pores called hydathodes.
A small example
On a hot, dry, windy afternoon a leafy plant loses water fast. On a rainy day the air already holds a lot of water vapour. So vapour moves out of the leaf more slowly, and transpiration falls.
Where marks go
The ICSE 2027 specimen paper gives 2 marks for defining transpiration. Its draft marking scheme reads: the loss of water as water vapour from the aerial parts of the plant. Say both "water vapour" and "aerial parts".
The 2024 ICSE Biology paper asked for two advantages of transpiration. Accepted answers included a cooling effect, a suction force that pulls water up, and the spread of water and minerals. CISCE's report on the 2024 ICSE Biology paper names "transpiration removes excess water from plants" as an incorrect answer. The same report names "osmosis" given where "guttation" was the answer.
Sources
Facts last checked against these sources on 30 September 2026.
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