Science — AI-generated practice question

Transport of Water in Tall Plants

Water absorbed by root hair cells moves into the xylem and is transported upward through two main mechanisms:

1. Root Pressure:
Cells in the root actively absorb mineral ions, lowering the water potential inside. Water enters by osmosis, generating a pressure that pushes water upward into the stem. Root pressure is sufficient only for short-distance transport in small/young plants.

2. Transpiration Pull (main force):
Leaves continuously lose water vapour through stomata (transpiration). This creates a suction force that pulls water upward through the xylem as a continuous column — from roots to leaves. This cohesion-tension mechanism is strong enough to transport water to the tops of tall trees.

Thus, root pressure provides an initial push, while transpiration pull is the dominant force responsible for upward water movement in tall plants.

---

• The question asks you to distinguish two roles — so clearly label and contrast both mechanisms. Examiners award marks for: (1) root pressure explained with osmosis, (2) transpiration pull explained with stomatal water loss/suction, (3) correct conclusion about which dominates in tall plants.
• The source passages focus on coordination/hormones; water transport is standard CBSE Class 10 Life Processes (Chapter 6, NCERT). Use correct terms: xylem, osmosis, transpiration, cohesion-tension.
• Do not write more than shown — boards penalise padding.