“The primary cell wall in plants is capable of growth, which gradually diminishes.”
EXplnation of Lines – From NCERT
🌱 What is the Primary Cell Wall?
The primary cell wall is the first layer of the cell wall that is formed in young, growing plant cells. It is:
- Thin, flexible, and stretchable.
- Composed mainly of cellulose, hemicellulose, pectin, and some proteins.
- Located outside the plasma membrane.
🔁 “Capable of Growth” — What It Means
This refers to the ability of the primary cell wall to expand and stretch as the plant cell grows.
- As water enters the cell (via osmosis), the turgor pressure increases.
- The primary wall loosens and expands, allowing the cell to enlarge.
- Specialized proteins and enzymes (like expansins) help in wall loosening during this phase.
🔸 In essence: The primary wall supports cell enlargement and organ growth in young tissues (like shoot and root tips).
📉 “Which Gradually Diminishes” — What It Means
As the plant cell matures:
- The cell finishes growing in size.
- The primary wall stiffens and thickens.
- A secondary cell wall may be deposited inside the primary wall (in certain cells like xylem).
- The plasticity (ability to stretch) of the primary wall decreases or stops altogether.
🔸 Therefore: The growth ability of the primary wall is temporary, active only during cell expansion, and fades as the cell fully differentiates.
📌 Summary
| Phase | Primary Cell Wall Behavior |
|---|---|
| Young cell | Flexible and growing |
| Mature cell | Becomes rigid and growth stops |
💬 Clarification
Your doubt:
“so diminish means growth of primary wall instead of wall itself”
SiddSir’s Reply:
Exactly! ✅
When we say: “Growth of the primary cell wall gradually diminishes”
We do not mean that the primary wall itself disappears or reduces.
We mean that:
- 🔹 The ability of the primary wall to support cell expansion — its growth potential — diminishes over time.
“Diminish” refers to the reduction in the wall’s ability to expand, not the disappearance or shrinkage of the wall itself.