Hard and strong

The idea

Sclerenchyma cells, mostly dead, have thick walls due to lignin that make them hard and strong; the tissue occurs in stems, leaf veins and the hard coverings of seeds and nuts.

Why is a walnut shell so hard?

A walnut shell protects the seed. It is very hard to break with your fingers.

What could make plant cells so hard and strong?

• Very thick walls
• Thin soft walls
• Large watery vacuoles

Thicken the wall

Add lignin to the wall of a cell. Watch the cell and the strength bar.

Sclerenchyma

Sclerenchyma cells have thick walls because of the deposition of lignin. This makes them hard and strong; it forms the woody structure. Most of these cells are dead. The tissue is found in stems, leaf veins, and the hard coverings of seeds and nuts, such as coconut husk and walnut shell.

Notes

Sclerenchyma: cells with thick lignified walls, hard and strong, mostly dead. Found in stems, leaf veins and hard coverings like coconut husk and walnut shell.

Check yourself

What makes the walls of sclerenchyma thick and hard?

Most sclerenchyma cells are…

Which of these is made largely of sclerenchyma?

• Pectin. Pectin thickens the corners of collenchyma cells.
• Cutin. Cutin forms the waxy cuticle.
• Lignin — correct. Yes.
• dead — correct. Yes. Thick walls and little inside.
• actively dividing. That describes meristematic cells.
• full of air spaces. That describes some parenchyma.
• The air spaces of a pond plant. Those are formed by parenchyma.
• A walnut shell — correct. Yes. NCERT names the coconut husk and walnut shell.
• A tendril that bends easily. Bending without breaking is the job of collenchyma.