Plant Tissues
NCERT Class 9 • Science • Chapter "Tissues"
Plant Tissues
A tissue is a group of cells with a similar structure that work together to perform a particular function. In plants, growth is limited to certain regions, so plant tissues are divided first into those that divide and those that have stopped dividing.
Meristematic and Simple Permanent Tissues
- Meristematic tissue consists of actively dividing cells with thin walls, dense cytoplasm and no vacuole.
- Apical meristem is at the tips of roots and shoots and increases length; lateral meristem increases girth; intercalary meristem lies at the base of leaves or internodes.
- Permanent tissue is formed when meristematic cells lose the ability to divide and take up a fixed role.
- Parenchyma has thin walled living cells and stores food; with chloroplast it becomes chlorenchyma and with air spaces aerenchyma, which helps aquatic plants float.
- Collenchyma has cells thickened at the corners and provides flexibility, which is why a stem can bend without breaking.
- Sclerenchyma has dead cells with thick lignified walls and gives strength and hardness, as in the husk of a coconut.
Complex and Protective Tissues
- Complex permanent tissue is made of more than one type of cell working together.
- Xylem conducts water and minerals upward from root to leaf and also gives mechanical support; most of it is made of dead cells.
- Xylem consists of tracheids, vessels, xylem parenchyma and xylem fibres.
- Phloem conducts food from leaves to the rest of the plant in both directions and is made mostly of living cells.
- Phloem consists of sieve tubes, companion cells, phloem parenchyma and phloem fibres.
- Epidermis is the outer protective layer, often covered by a waxy cuticle that reduces water loss.
- Small openings called stomata in the epidermis allow exchange of gases and loss of water vapour in transpiration.
- In older stems the epidermis is replaced by cork, whose dead cells give strong protection against injury and water loss.
| Tissue | Function | Living or Dead |
|---|---|---|
| Parenchyma | Storage and basic packing | Living |
| Collenchyma | Flexibility | Living |
| Sclerenchyma | Strength and hardness | Dead |
| Xylem | Water transport upward | Mostly dead |
| Phloem | Food transport both ways | Mostly living |
Meristematic tissue — plant tissue made of actively dividing cells, responsible for the growth of the plant.
Hindi me samjhein
जाइलम जल ऊपर की ओर ले जाता है और इसकी अधिकांश कोशिकाएं मृत हैं। फ्लोएम भोजन दोनों दिशाओं में ले जाता है और इसकी अधिकांश कोशिकाएं जीवित हैं।
Exam me kaise aata hai
- Which tissue conducts water upward — xylem
- Which tissue conducts food both ways — phloem
- Which tissue gives flexibility to a stem — collenchyma
- Openings in the epidermis for gas exchange are — stomata
UPSC/State PSC ke liye
- Xylem can be made of dead cells because water moves through hollow tubes by physical pull, whereas phloem must stay alive since food transport needs energy.
- Aerenchyma gives aquatic plants buoyancy, which is a clear example of a tissue shaped by the environment the plant lives in.
Yahan confuse hote hain
✗ Phloem conducts water | Phloem conducts food; xylem conducts water | ✓
✗ Sclerenchyma is a living tissue | Sclerenchyma cells are dead | ✓
✗ Xylem transports in both directions | Xylem moves water upward; phloem moves food both ways | ✓
Ek nazar me
- Meristematic tissue divides; permanent tissue has a fixed role.
- Parenchyma stores, collenchyma bends, sclerenchyma strengthens.
- Xylem carries water upward and is mostly dead; phloem carries food both ways and is living.
- Epidermis with cuticle protects; stomata allow gas exchange.