Path of Water Across the Root

Estimated time: 5 minutes

Maharashtra State Board: Class 12

Key Points: Path of Water Across the Root

Water enters root hair cells via imbibition → diffusion → osmosis; cell becomes turgid, TP increases, DPD decreases.
Water moves inward due to a DPD gradient - each inner cortical cell has higher DPD and pulls water from the outer cell, continuing up to the pericycle → xylem.
Root Pressure - hydrostatic pressure built in root cells forces water into the xylem and conducts it upward against gravity.
Apoplast Pathway - water moves through cell walls & intercellular spaces (non-living); fast but non-selective; blocked at endodermis by Casparian strip.
Symplast Pathway - water moves cell to cell via plasmodesmata (living); slower but selective and controlled.
Casparian Strip (suberized layer in endodermis) blocks the apoplast pathway, forcing water into the symplast before entering the vascular tissue.
Secondary roots (from pericycle) bypass the Casparian strip, providing a direct apoplastic route to xylem and phloem.