Anatomy of Flowering Plants | NEET Quality Hinglish Notes | Class 11 Biology

1. Introduction to Tissues

Jab hum living organisms ko dekhte hain, to unke external structures me similarities aur differences easily notice kiye ja sakte hain, chahe wo plants ho ya animals. Similarly, agar hum internal structure examine karein, to bhi bahut saari similarities aur variations milti hain. Ye chapter focus karta hai higher plants ke internal structure aur functional organisation par, jo plant anatomy kehlata hai. Plants me, cell basic unit hai, aur cells tissues me organized hote hain, jo aage jaake organs banate hain. Har organ me plant ka distinct internal structure hota hai. Angiosperms me, monocots aur dicots ke beech noticeable anatomical differences hote hain. Plants ke internal structures sirf different nahi hote, balki ye various environments ke liye adapt bhi hote hain, jo plant ko uske habitat me survive aur effectively function karne me help karte hain.

2. Cellular Tissue Organization in Plants

Plants me, tissues sirf cell types ke basis par classify nahi hote, balki ye plant body me unke location ke hisaab se bhi vary karte hain. Inka structure aur function closely related hota hai jahan ye paye jaate hain. Structure aur position ke basis par, plants me teen main tissue systems hote hain.

Pehla, epidermal tissue system, jo plant ka outer protective layer banata hai.
Dusra, ground ya fundamental tissue system, jo plant body ka major hissa banata hai aur support, storage, aur photosynthesis me involved hota hai.
Teesra, vascular ya conducting tissue system, jo plant me water, minerals, aur nutrients ka transport karta hai.

In teeno tissue systems me special adaptations hoti hain jo unke specific functions ko efficiently perform karne me help karti hain.

Plant Surface Protective Layer i.e. Epidermal Tissue

The system of epidermal tissue plants ke poore plant body ki outermost protective covering banata hai aur yeh epidermal cells, stomata, aur epidermal appendages jaise trichomes aur hairs se bana hota hai. Epidermis primary plant body ki outer layer hoti hai aur usually single-layered hoti hai, jo elongated, compactly arranged parenchymatous cells se bani hoti hai jisme cell wall ke saath thoda cytoplasm aur ek bada central vacuole hota hai. Epidermis ka outer surface aksar waxy, thick layer se covered hota hai, jise cuticle kehte hain, jo water loss ko rokta hai, lekin roots me yeh cuticle nahi hota. Leaves ke epidermis me special structures hote hain, jise stomata kehte hain, jo transpiration aur gaseous exchange ko control karte hain. Har stoma do bean-shaped guard cells se bana hota hai jo stomatal pore ko surround karte hain; lekin grasses me, guard cells dumbbell-shaped hote hain. Guard cells ki outer walls patli hoti hain, jabki inner walls thickened hoti hain, jo pore ko open aur close karne me help karti hain. Guard cells me chloroplasts bhi hote hain jo stomatal movements ko regulate karte hain. Guard cells ke around kuch specialised epidermal cells hote hain, jise subsidiary cells kehte hain, aur milke stomatal pore, guard cells, aur subsidiary cells stomatal apparatus banate hain. Epidermis me hairs bhi hote hain: roots me yeh unicellular root hairs hote hain jo soil se water aur minerals absorb karne me help karte hain, jabki stem me yeh trichomes kehlate hain. Trichomes usually multicellular hote hain aur branched ya unbranched, soft ya stiff, aur kabhi kabhi secretory bhi hote hain. Yeh excessive transpiration ko rok kar water loss ko kam karte hain aur plant ko protection bhi dete hain.

Internal Support and Storage Tissue in Plants, Ground Tissue

Plant ke saare tissues, epidermis (outer covering) aur vascular bundles (xylem aur phloem) ko chhod ke, milke ground tissue banate hain. Yeh tissue mainly simple tissues jaise parenchyma, collenchyma, aur sclerenchyma se bana hota hai.

Parenchyma cells commonly plant ke kai parts me paye jate hain, jaise cortex (stem ya root ki outer layer), pericycle (endodermis ke andar wali layer), pith (stem ka central part), aur medullary rays (vascular bundles ke beech ka tissue). Primary stems aur roots me yeh cells support aur storage provide karte hain.

Leaves me, ground tissue thin-walled cells se bana hota hai jo chloroplasts contain karte hain. Yeh specialised tissue mesophyll kehlata hai aur mainly photosynthesis ke liye responsible hota hai.

Vascular Tissue System – Transport and Support in Plants

Plants ka vascular system complex tissues jaise xylem aur phloem se bana hota hai, jo milke vascular bundles banate hain. Dicotyledonous stems me ek special layer hoti hai jise cambium kehte hain, jo xylem aur phloem ke beech hoti hai. Cambium ki presence ki wajah se yeh vascular bundles secondary xylem aur phloem produce kar sakte hain, jo plant ko thickness me grow karne me help karta hai. Isliye inhe open vascular bundles kehte hain.

Iske contrast me, monocotyledonous stems me vascular bundles me cambium nahi hota. Kyunki yeh secondary tissues nahi bana sakte, inhe closed vascular bundles kehte hain.

Xylem aur phloem ka arrangement bhi vary kar sakta hai. Jab xylem aur phloem alag-alag radii ke along alternate placed hote hain, toh pattern ko radial arrangement kehte hain, jo usually roots me dekha jata hai. Dusri taraf, conjoint vascular bundle me xylem aur phloem ek hi radius ke along saath hote hain, jo commonly stems aur leaves me paya jata hai. Aise bundles me, phloem generally xylem ke outer side me located hota hai.

3. Plant Anatomy – Structure of Dicot and Monocot Plants

Ye clearly samajhne ke liye ki tissues plant ke alag-alag parts me kaise arranged hain, roots, stems, aur leaves ke transverse sections (cross-sections) ko examine karna helpful hota hai. In organs ke mature zones ke sections study karne se different tissues, jaise epidermis, ground tissue, aur vascular tissues, ki organization aur arrangement ko dekhna easy ho jata hai. Ye approach samajhne me help karta hai ki har tissue plant parts ke structure aur function me kaise contribute karta hai.

Dicot Root – Structure and Organization

Agar hum sunflower root ko cross-section me dekhen, toh internal tissue organization layer by layer clearly samajh me aata hai. Sabse outer layer ko epiblema kehte hain, aur iske kai cells unicellular root hairs banate hain, jo water aur minerals ke absorption me help karte hain. Epiblema ke andar cortex hota hai, jo kai layers ke thin-walled parenchyma cells se bana hota hai jisme intercellular spaces hote hain jo gas exchange allow karte hain. Cortex ki innermost layer ko endodermis kehte hain, jo single layer ke barrel-shaped cells se bana hota hai bina kisi space ke. Endodermal cells ki walls me suberin hota hai, ek waxy, water-impermeable material, jo Casparian strips banata hai aur vascular system me water ke movement ko control karta hai.

Endodermis ke just andar, kuch layers ke thick-walled parenchyma cells hote hain, jise pericycle kehte hain, jo lateral roots aur vascular cambium ke formation me important role play karte hain during secondary growth. Center me jo pith hota hai, wo usually chhota ya barely visible hota hai. Xylem aur phloem ke beech me, parenchyma cells conjunctive tissue banate hain. Typically, 2-4 patches of xylem aur phloem hote hain, aur later, unke beech ek cambium ring develop hota hai.

Endodermis ke andar located saare tissues, including pericycle, vascular bundles, aur pith, milke stele banate hain, jo root ka central part hai aur transport aur support ke liye responsible hai.

Monocot Root – Structure and Organization

Monocot root apni basic structure me dicot root ke kaafi similar hoti hai. Isme saare major tissues hote hain jaise epidermis, cortex, endodermis, pericycle, vascular bundles, aur pith. Lekin, kuch differences bhi hote hain. Monocot roots me usually 6 se zyada xylem bundles hote hain (jise polyarch kehte hain), jabki dicot roots me xylem bundles kam hote hain. Monocot roots me pith bada aur well-developed hota hai, jabki dicots me yeh chhota ya inconspicuous hota hai. Ek aur important difference yeh hai ki monocot roots secondary growth show nahi karte, matlab yeh age ke saath utni thick nahi hoti jitni dicot roots hoti hain.

Dicot Stem – Structure and Organization

Transverse section of a young dicotyledonous stem uske tissues ki organization ko clearly reveal karta hai. Epidermis stem ki outermost protective layer banata hai. Yeh thin cuticle se covered hota hai aur isme trichomes (hair-like structures) aur kuch stomata gas exchange ke liye ho sakte hain. Epidermis ke just neeche cortex hota hai, jo multiple layers se bana hota hai aur teen sub-zones me divided hota hai.

Outer hypodermis kuch layers ke collenchyma cells se bana hota hai, jo young stem ko mechanical support provide karte hain. Hypodermis ke neeche cortical layers rounded, thin-walled parenchyma cells se bani hoti hain jisme noticeable intercellular spaces hote hain. Cortex ki innermost layer ko endodermis kehte hain, jo starch grains me rich hoti hai aur isliye isse starch sheath bhi kehte hain.

Endodermis ke inner side aur phloem ke just upar pericycle hota hai, jo semi-lunar patches ke form me sclerenchyma present hota hai. Vascular bundles ke beech kuch layers radially arranged parenchyma cells ki hoti hain, jise medullary rays kehte hain, jo water aur nutrients ke radial transport me help karte hain.

Vascular bundles khud ek ring me arranged hote hain, jo dicot stems ka typical feature hai. Har bundle conjoint hota hai, matlab xylem aur phloem saath hote hain, open (secondary growth ke liye cambium ke saath) aur endarch protoxylem hota hai (protoxylem center ki taraf). Stem ka central portion pith se occupied hota hai, jo rounded parenchyma cells se bana hota hai jisme bade intercellular spaces hote hain, providing storage aur support.

Monocot Stem – Structure and Organization

Monocot stem me dicot stem ke comparison me kuch distinct features hote hain. Iska hypodermis sclerenchyma cells se bana hota hai, jo mechanical strength provide karta hai. Andar, ek large amount ka parenchymatous ground tissue hota hai, jo loosely arranged hota hai aur stem ka majority occupy karta hai, jo storage aur support provide karta hai.

Vascular bundles monocot stems me ground tissue me scattered hote hain, ring me arranged nahi hote. Har vascular bundle conjoint (xylem aur phloem saath) aur closed hota hai, matlab isme cambium nahi hota aur yeh secondary tissues nahi bana sakta. Peripheral bundles jo edge ke near hote hain, usually smaller hote hain, jabki central bundles bade hote hain. Dicot stems ke opposite, phloem parenchyma absent hota hai, aur kuch water-containing cavities vascular bundles ke andar hoti hain, jo water storage aur transport me help karti hain.

Dicot Leaf (Dorsiventral) – Structure and Organization

Vertical section of a dorsiventral (dicot) leaf uske lamina ke through teen main parts show karta hai: epidermis, mesophyll, aur vascular system. Epidermis leaf ke upper surface (adaxial epidermis) aur lower surface (abaxial epidermis) dono ko cover karta hai aur water loss se protection ke liye noticeable cuticle hoti hai. Abaxial epidermis me usually adaxial side ke comparison me zyada stomata hote hain, aur kabhi-kabhi adaxial epidermis me stomata completely absent bhi ho sakte hain.

Upper aur lower epidermis ke beech ka tissue mesophyll kehlata hai, jo chloroplasts contain karta hai aur photosynthesis karta hai. Mesophyll parenchyma cells se bana hota hai aur do types ka hota hai: palisade parenchyma aur spongy parenchyma. Palisade parenchyma leaf ke upper side (adaxial) ke near hota hai aur elongated cells se bana hota hai, jo vertically aur parallel arranged hote hain, jo maximum light absorption me help karte hain. Palisade layer ke neeche spongy parenchyma hota hai, jo oval ya round, loosely arranged cells se bana hota hai aur lower epidermis tak extend karta hai. In cells ke beech me kai air spaces aur cavities hote hain, jo gas exchange me aid karte hain.

Vascular system me vascular bundles hote hain, jo veins aur midrib me dekhe ja sakte hain. Vascular bundles ka size veins ke size pe depend karta hai, aur dicot leaves me reticulate venation ke saath, veins ki thickness vary karti hai. Har vascular bundle thick-walled bundle sheath cells ke layer se surrounded hota hai for protection aur support. Vascular bundle me, xylem generally upper side me located hota hai, jabki phloem bundle ke lower side me hota hai.

Monocot Leaf (Isobilateral) – Structure and Organization

Isobilateral (monocot) leaf ka anatomy dorsiventral (dicot) leaf ke similar hota hai, lekin kuch important differences hote hain. Isobilateral leaf me stomata epidermis ke upper (adaxial) aur lower (abaxial) surfaces dono par present hote hain, unlike dorsiventral leaves jahan stomata mostly lower surface par hote hain. Mesophyll palisade aur spongy parenchyma me divided nahi hota; instead, yeh throughout uniform parenchyma cells se bana hota hai.

Grasses me, veins ke along kuch adaxial epidermal cells transform hokar large, empty, colourless cells ban jate hain, jise bulliform cells kehte hain. Yeh cells water conservation me help karte hain: jab turgid (paani se full) hote hain, leaf open rehti hai, aur jab flaccid (water-stressed) hoti hai, leaf andar curl karti hai taaki water loss kam ho.

Monocot leaves me jo parallel venation hoti hai, wo vascular bundles me reflected hoti hai, jo generally leaf ke throughout similar size ke hote hain, except main veins jahan bundles bade ho sakte hain. Yeh arrangement water aur nutrients ke efficient transport me help karta hai.

3. Chapter Overview – Key Points and Concepts

Ek plant ke anatomical view se pata chalta hai ki yeh different types ke tissues se bana hota hai, jo har ek specific functions perform karte hain. Broadly, plant tissues ko meristematic tissues aur permanent tissues me classify kiya jata hai. Meristematic tissues me apical, lateral, aur intercalary meristems shamil hote hain, jo growth ke liye responsible hote hain. Permanent tissues simple (jaise parenchyma, collenchyma, sclerenchyma) ya complex (jaise xylem aur phloem) ho sakte hain aur functions perform karte hain jaise food assimilation aur storage, water, minerals aur photosynthates ka transport, aur mechanical support.

Plant tissues teen main tissue systems me organized hote hain: epidermal, ground, aur vascular. Epidermal tissue system me epidermal cells, stomata, aur epidermal appendages shamil hote hain, jo plant ki outer protective layer banate hain. Ground tissue system plant ka bulk banata hai aur isme teen zones hote hain: cortex, pericycle, aur pith, jo storage, support, aur metabolic functions provide karte hain. Vascular tissue system xylem aur phloem se bana hota hai, jo conducting tissues ke tarah kaam karte hain, water, minerals, aur food transport karte hain.

Vascular bundles ka structure aur arrangement cambium ki presence aur xylem aur phloem ke position pe depend karta hai. Yeh variation especially monocotyledonous aur dicotyledonous plants ko compare karne par dikhai deta hai. Yeh plants vascular bundles ke type, number, aur location me different hote hain. Additionally, secondary growth, jo roots aur stems ki thickness increase karta hai, mostly dicotyledonous roots aur stems me hota hai, lekin generally monocotyledons me absent hota hai.