↑ Back to Topics
1. Introduction to Plant Tissues
Tissue kya hota hai?
Tissue = Cells ka ek group jo ek saath kaam karta hai ek specific function perform karne ke liye.
Type 1
🌿 Plant Tissue
Type 2
🐾 Animal Tissue
Tissues ki Importance kyun hai?
- Multicellular organisms mein division of labour create karta hai.
- Individual cells ka workload kam karta hai.
- Tissues → Organs → Organ Systems → Improved body organization.
↑ Back to Topics
2. Classification of Plant Tissues
🌿 Plant Tissues
Meristematic Tissue
Apical Meristem
Lateral Meristem
Intercalary Meristem
Permanent Tissue
Simple Permanent
Parenchyma
Collenchyma
Sclerenchyma
Complex Permanent
Xylem (Tracheids, Vessels, Xylem Fiber, Xylem Parenchyma)
Phloem (Sieve Tubes, Companion Cells, Phloem Parenchyma, Phloem Fiber)
Protective Tissue
Epidermis
Cork
Yaad rakho: Meristematic = dividing cells (growth ke liye) | Permanent = mature, non-dividing cells (specific kaam ke liye)
↑ Back to Topics
3. Meristematic Tissue
Meristematic tissues wo cells hain jo continuously divide kar sakte hain — plant growth ke liye responsible!
Characteristics (Pehchaan)
- 📍 Occurrence: Plant ke growing regions mein — root, shoot etc.
- 🔷 Shape: Spherical, oval, ya rectangular.
- Dense cytoplasm + Large nuclei hote hain.
- Intercellular spaces aur vacuoles absent hote hain.
- Active cells hote hain.
- Cell wall cellulose se bani hoti hai.
| Type | Location | Function |
|---|---|---|
| Apical Meristem | Shoot apex aur Root apex pe | Root aur shoot ki length badhata hai |
| Lateral Meristem | Bark ke neeche | Root aur stem ki thickness badhata hai |
| Intercalary Meristem | Leaves ki base ya internodes (grasses) mein | Leaves aur internodes ki length badhata hai (e.g. leaf blades) |
📌 Important Points
- Protoderm: Apical meristem ka ek part jo root aur shoot mein hota hai → Epidermis banata hai.
- Cambium: Xylem aur Phloem ke beech ka lateral meristematic tissue → Secondary xylem + Secondary phloem banata hai → Secondary growth (plant ki girth badti hai).
↑ Back to Topics
4. Permanent Tissue
Kya hota hai?
- Non-dividing cells jo mature ho gaye hain aur specific functions perform karte hain.
- Meristematic tissue differentiation process se permanent tissue mein convert hota hai.
- 📍 Occurrence: Roots, stem, leaves etc.
- 🔷 Shape: Round, oval, elongated, polygonal ya irregular.
- Cell wall thin ya thick hoti hai — large central vacuoles hote hain.
- Functions: Support, storage, conduction, aur protection.
↑ Back to Topics
5. Simple Permanent Tissue
Simple Permanent Tissue = Homogenous tissue — ek hi type ke cells, same origin, structure aur function.
Type 1
🟢 Parenchyma
Type 2
🔵 Collenchyma
Type 3
⬛ Sclerenchyma
↑ Back to Topics
6. Parenchyma Tissue
Basic Info
- 📍 Occurrence: Puri plant body mein — cortex, pith of roots & stems, leaf mesophyll, vascular bundles.
- Living cells hote hain.
- Large lumen hota hai.
Functions
- 🍎 Food storage tissue hai — main function.
- Kuch mein chlorophyll hota hai → Chlorenchyma kehte hain (photosynthesis karta hai).
- Loosely packed hone par intercellular spaces hote hain → Aerenchyma kehte hain.
- Aerenchyma buoyancy provide karta hai — plant parts ko float karne mein help karta hai (e.g. water plants).
↑ Back to Topics
7. Collenchyma Tissue
Basic Info
- 📍 Occurrence: Leaf stalks, stem of dicots epidermis, vascular bundle of dicot leaf.
- Cells living, elongated hote hain — corners pe irregularly thickened.
- Intracellular spaces bahut kam hote hain.
- Narrow (moderate) lumen hota hai.
Functions
- 💪 Mechanical tissue — plant ko mechanical strength deta hai.
- 🌀 Flexibility deta hai — plant parts ko bend hone deta hai.
- Example: Tendrils aur climbing plants ke stems.
↑ Back to Topics
8. Sclerenchyma Tissue
Basic Info
- 📍 Occurrence: Stems, vascular bundles ke around, leaf veins, hard coverings (e.g. Bark, Coconut husk).
- Dead Tissue — bahut hard aur rigid hoti hai.
- Lumen bahut narrow ya almost absent (obliterated) hota hai.
- Toughness provide karta hai.
Functions
- 🏋️ Mechanical support aur rigidity deta hai plant ko.
- Sclereids: Seeds ki hardness ke liye aur walnut ke shell ke liye responsible.
- Cell walls mein Lignin deposit hota hai → cement ki tarah kaam karta hai → extreme hardness.
Lignin ek chemical hai jo cell walls mein thicken ho jaata hai → Sclerenchyma ko bahut hard aur rigid banata hai. Ise cement of cell wall bhi kehte hain!
| Feature | Parenchyma | Collenchyma | Sclerenchyma |
|---|---|---|---|
| Cell type | Living | Living | Dead |
| Cell wall | Thin | Thickened at corners | Thick (Lignin) |
| Lumen | Large | Narrow/Moderate | Very narrow/Absent |
| Main function | Food storage | Flexibility + Strength | Mechanical support |
| Intercellular space | Present (sometimes) | Very little | Absent |
↑ Back to Topics
9. Complex Permanent Tissue
Kya hota hai?
Alag-alag cell types mile hue hote hain jo ek unit ki tarah kaam karte hain ek specific function ke liye.
Type 1: Xylem Type 2: Phloem
Vascular Bundles = Xylem + Phloem ek saath — collectively inhe vascular bundles kehte hain!
↑ Back to Topics
10. Xylem
Kya kaam karta hai?
- 🚿 Water + Nutrients roots se leaves tak transport karta hai — One-way conduction (upward).
- Transpiration pull se kaam karta hai.
- Plant ko support bhi deta hai.
Composition (Kya kya hota hai isme?)
Component 1
Tracheids
Component 2
Vessels
Component 3
Xylem Fiber
Component 4 ✅ Living
Xylem Parenchyma
⚠️ Sirf Xylem Parenchyma hi living tissue hai — baaki sab dead hote hain.
Transpiration Pull kaise kaam karta hai?
- Leaves se water evaporate hota hai → Transpiration creates pull.
- Cohesion (same molecules ke beech attraction) — water molecules ek doosre se chipke rehte hain.
- Adhesion (dissimilar molecules ke beech attraction) — water xylem walls se chipkta hai.
- Osmosis roots mein water push karta hai — column banta hai.
↑ Back to Topics
11. Phloem
Kya kaam karta hai?
- 🍎 Food (prepared) leaves se plant ke different parts tak transport karta hai — Two-way conduction (upward + downward).
Composition
Component 1
Sieve Tubes (Non-nucleated at maturity)
Component 2
Companion Cells
Component 3
Phloem Parenchyma
Component 4 ❌ Dead
Phloem Fibre
⚠️ Sirf Phloem Fibre dead tissue hai — baaki sab living hote hain.
| Feature | Xylem | Phloem |
|---|---|---|
| Conducts | Water + Minerals | Food (Sugars) |
| Direction | One-way (Root → Leaf) | Two-way |
| Cell wall | Thick (Lignin) | Thin (Cellulose) |
| End walls | No end walls between cells | End walls with perforations |
| Dead part | All except Xylem Parenchyma | Only Phloem Fibre |
↑ Back to Topics
12. Protective Tissue
Kya hoti hai?
Specialized tissues jo plant body ki outermost layers banate hain — mechanical damage, pathogens aur water loss se protect karte hain.
Epidermis Cork
↑ Back to Topics
13. Epidermis
Basic Info
- Plant organs ki outermost layer of cells.
- 📍 Occurrence: Sabhi plant parts — leaves, flowers, stem, roots.
Desert Plants mein
Cuticle
- Cutin — waxy material, water resistant.
- Layer of cutin = Cuticle.
- Water loss, injury aur fungi se protection.
- Dry habitats → thicker epidermis.
Roots mein
Root Hair
- Epidermal cells hair-like structures banate hain.
- Root ki surface area badhate hain.
- Water absorption zyada efficient hoti hai.
Leaves mein
Stomata
- Epidermal cells stomata banate hain.
- Stomata Guard Cells se guarded hote hain.
- Guard cells = kidney-shaped structures.
- Gaseous exchange regulate karte hain.
↑ Back to Topics
14. Cork
Kya hota hai?
- Plant ka external protective tissue.
- Dead cells hote hain — compactly arranged.
- Cell walls Suberin se coated hoti hain.
- 📍 Occurrence: Stem aur tree trunks ki outer covering.
Functions
- Mature roots aur shoots ko protection deta hai.
- Suberin ek protective barrier ki tarah kaam karta hai.
- Suberin water aur gases ko cork cells se bahar nahi jaane deta.
Phellem = Cork cells | Phellogen = Cork cambium (jo cork banata hai) | Phelloderm = Inner layer
↑ Back to Topics
15. Transpiration vs Guttation
| Feature | Transpiration | Guttation |
|---|---|---|
| Water lost as | Water vapour | Water droplets |
| Through | Stomata, cuticle aur lenticels | Hydathodes (present on leaf sides) |
| Effect on turgidity | Turgidity loss → Wilting | No effect on turgidity |
| Plant body | Cools the plant | No cooling |
| Time | Day time | Night time |
Quick Trick: Transpiration = T for Thinning vapour, daytime, turgidity loss | Guttation = G for Gross drops, night time, no cooling!