Water in plants is removed as water vapour through the process of

Step 1: Analyze the question The question asks about the process by which plants lose water as water vapour. The key words are "water in plants" and "water vapour."

Step 2: Explain the concepts Let's look at each option:

• Diffusion: The movement of particles from a region of high concentration to a region of low concentration. It is a general process, not specific to water loss in plants.
• Osmosis: The movement of water across a semi-permeable membrane from a region of high water potential to one of low water potential. It moves water into and between cells, but it is not the loss of water vapour.
• Evaporation: The change of liquid water into vapour. This is a physical process and it does occur inside the leaf (at the surface of mesophyll cells), but it is only one step in the overall process.
• Transpiration: The loss of water vapour from the aerial parts of a plant, mainly through the stomata of the leaves (also through the cuticle and lenticels).

Step 3: Work through the process

1. Roots absorb water from the soil by osmosis.
2. Water travels up the xylem to the leaves.
3. Water evaporates from the moist surfaces of mesophyll cells into the air spaces of the leaf.
4. Water vapour diffuses out through the stomata into the atmosphere.

The whole sequence of losing water vapour from the plant is called transpiration.

Step 4: Answer The correct answer is D. transpiration.

Tip: Remember that "trans" means across or through, and "spire" relates to breathing. So transpiration is like the plant "breathing out" water vapour. In exams, if the question says "water vapour lost from plants," think transpiration. If it says "water absorbed by roots," think osmosis.