Question

Apoplast pathway is faster than the symplast pathway because

• A. it is composed of living parts of the plant
• B. it is blocked at the endodermis by the casparian strip
• C. water movement occurs by osmosis
• D. water movement occurs by passive diffusion

Answer 1

The correct option is D water movement occurs by passive diffusion

Apoplast constitutes the non-living parts of the cell. There is no barrier to water movement (since the cortical cells are loosely packed) and water moves in bulk by diffusion through cell wall and intercellular spaces. However, when the water reaches the endodermis which has a band of suberised matrix called the casparian strip, it chooses to follow the symplast pathway and not the apoplast pathway to reach the xylem vessels.

Since the apoplast pathway does not require the entry of water through the cell membrane, it is relatively faster than the symplast pathway.