Question

How is water exchanged between cells even though lignified secondary cell walls are impermeable to water?

Answer 1

Lignified walls:

1. Lignin is a waterproof polymer which is present in cell wall to strengthen the cell.
2. Water and other dissolved minerals enter the plants through the soil from the roots and are transported up the plant through the xylem.
3. Water reaches the lignified walls that are impermeable with water.
4. So for the exchange of water takes place through the small minute opening called as pits.
5. Pits are thin areas on the secondary cell walls of plants. They have depressions on the wall.
6. They help in transport of water and minerals up to the top of the plant.
7. Pits are of two types: simple pits and bordered pits.
8. Bordered pits are thickened over the pit cavity.
9. Simple pit does not have borders.