Plant Physiology for ICSE Class 10: Absorption by Roots

Plant Structure

• Root System: Underground part of a plant; essential for absorption and anchoring.
• Shoot System: Above-ground part; includes stem, leaves, flowers, fruits.

Functions of Roots

1. Anchoring: Holds the plant in the ground.
2. Absorption: Takes in water and minerals from the soil.
3. Transport: Moves water and minerals up to the stems via xylem.
4. Food Transport: Uses phloem to move prepared food from leaves to roots.
5. Storage: Some roots store food.

Importance of Water and Minerals

• Photosynthesis: Water is essential for glucose synthesis in leaves.
• Transpiration: Cooling mechanism via water loss as vapor, creates suction force.
• Transportation: Xylem and phloem transport nutrients and water.
• Mechanical Stiffness: Plants appear healthy and stiff when cells are turgid.

Characteristics of Roots for Absorption

1. Root Hairs: Increase surface area for absorption.
2. Cell Sap: Higher solute concentration inside root cells draws in water.
3. Thin Cell Walls: Permeable to water.

Phenomena Assisting Absorption

• Imbibition: Water absorption by surface attraction, e.g., swelling of wood.
• Diffusion: Movement from higher to lower concentration.
• Osmosis: Water movement through a semi-permeable membrane.
• Active Transport: Movement from lower to higher concentration using energy.

Terms

• Turgidity: Condition when plant cells are full of water.
• Flaccidity: Condition when plant cells are shrunken or dehydrated.