Science — AI-generated practice question

Water moves from soil to leaves through the following steps:

1. Absorption by Roots: Root hair cells absorb water from the soil by osmosis. The concentration of cell sap in root hairs is higher than soil water, so water enters by osmosis.

2. Root Pressure: Osmotic pressure in root cells pushes water upward into the xylem. This force, called root pressure, helps in the initial upward movement of water.

3. Role of Xylem: Xylem vessels form a continuous network of tubes from roots to leaves. Water travels upward through these hollow, dead cells. Xylem is responsible for transport of water and dissolved minerals.

4. Transpiration Pull: Leaves constantly lose water vapour through stomata (transpiration). This creates a suction force that pulls water upward through the xylem from roots to leaves. This is the most important force for water movement in tall trees.

Thus, root pressure pushes water up from below, while transpiration pull draws it upward from above, with xylem acting as the conducting channel.

Source: Chapter 5 – Life Processes, Section 5.4 Transportation

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• The examiner expects all three concepts — root pressure, transpiration pull, and xylem — each clearly explained. Missing any one costs marks.
• Root pressure alone cannot explain water rising to great heights in tall trees; transpiration pull is the dominant force — mention this.
• Xylem's role must be stated as the conducting tissue, not just named.
• Do not mix up xylem (water) and phloem (food) — a common error.
• Osmosis should be mentioned for root absorption to show understanding of the mechanism.