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State Board · Class 11 · Biology

Lesson 8: Plant Tissues and Anatomy

7 concepts · 56 practice questions with answers · Free to read

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Tissues and meristematic tissue

Link to Std 9–10

Std 9–10 introduced tissues simply; here we study each tissue and the internal structure of root, stem and leaf in detail.

From daily life

Fresh bricks raise a new wall; likewise a group of young, dividing cells builds new parts of a plant – the meristematic tissue.

Simple definition

Tissue = a group of cells with a common origin and function. By ability to divide: meristematic and permanent.

Classification of meristemsApicalIntercalary (node)Lateral (girth)root apicalOriginPromeristem → Primary → SecondaryPositionApical = length growthIntercalary = at nodes (monocots)Lateral = girth (cambium)FunctionProtoderm → epidermisProcambium → primary xylem, phloemGround meristem → cortex, pithCells: thin wall, dense cytoplasm,big nucleus, tiny vacuoles, no gaps

In the figure : Classification of meristems: origin, position and function.

Rule 1 : Features of meristematic tissue — Young, living, dividing cells; polyhedral (isodiametric); no intercellular spaces; thin cellulose wall; dense cytoplasm; large nucleus; tiny vacuoles; high metabolism.

  • Easy : Thin wall + dense cytoplasm + big nucleus = meristem.
  • Medium : Cells just behind a root tip divide.
  • Exam-type (CET) : Meristem cells lack a large vacuole.

Rule 2 : Classification: origin, position, function — Origin: primordial (promeristem) → primary → secondary. Position: apical (length), intercalary (near nodes, monocots), lateral (girth; e.g. cambium). Function: protoderm → epidermis; procambium → primary xylem/phloem; ground meristem → cortex, pith.

  • Easy : Secondary meristem is always lateral; e.g. cork cambium.
  • Medium : Intercalary tissue is short-lived; seen in grasses.
  • Exam-type (CET) : Shoot apex is terminal; root apex lies behind the cap (subterminal).
Remember

Three criteria: origin, position, function; apical = height, lateral = girth.

Common mistake and CET trap

‘Lateral meristem increases length’ is wrong (girth). Trap: ‘meristem cells have a large vacuole’ is wrong.

Shortcut

Memory clue : "A-L-I: Apical = Ascend, Lateral = Large girth, Intercalary = Internode".

Spot the difference

TypeRoleExample
ApicalLength growthShoot/root tip
IntercalaryNode growthGrass
LateralGirth growthCambium

Practice questions

Easy
  1. 1What is a tissue?
  2. 2Two features of meristem.
  3. 3Role of apical meristem?
Medium
  1. 4Example of lateral meristem.
  2. 5What does protoderm form?
  3. 6Procambium forms?
Challenging
  1. 7Where is intercalary meristem?
  2. 8Primary vs secondary meristem.
Show answers (try them yourself first)
  1. 1A group of cells with common origin and function.
  2. 2Thin wall; large nucleus.
  3. 3Increases length.
  4. 4Cambium; cork cambium.
  5. 5Epidermis.
  6. 6Primary xylem and phloem.
  7. 7Near nodes; mostly monocots.
  8. 8Primary at tips from the start; secondary arises later from permanent tissue, lateral.

Simple permanent tissues

From daily life

Brick, sand and rope each do a different job; in plants parenchyma fills, collenchyma gives flexible support, sclerenchyma gives hard support.

Simple definition

Permanent tissue = cells that lost the ability to divide and took a fixed shape and function. Simple = one cell type: parenchyma, collenchyma, sclerenchyma.

Parenchyma, collenchyma, sclerenchymaParenchymaCollenchymaSclerenchymaliving; thin wallhas air spacesstores food, water; photosynthesisliving; corner thickeningno spacessupports young stem, petioledead; lignified thick wallfibres and sclereidsmain support; jute, flaxAll three are simple tissues: one cell typeParenchyma, collenchyma = living | sclerenchyma = deadCollenchyma is usually absent in monocots and roots

In the figure : Three simple tissues: wall structure and function.

Rule 1 : Parenchyma and collenchyma — Parenchyma: living, thin cellulose wall, large vacuole; intercellular spaces; linked by plasmodesmata; stores food and water; photosynthesis; gas exchange. Collenchyma: living; extra cellulose and pectin at corners; no spaces; flexible support to young stems and petioles; absent in monocots and roots.

  • Easy : Parenchyma = least specialised.
  • Medium : Collenchyma = living mechanical tissue.
  • Exam-type (CET) : Dedifferentiated parenchyma forms cambium and cork cambium.

Rule 2 : Sclerenchyma — Dead, thick lignified wall, no nucleus. Two types: fibres (long, tapering, in bundles; jute, flax, hemp) and sclereids (short, deep pits; seed coats, shells). The main supporting tissue; stiffens leaves.

  • Easy : Sclerenchyma is dead; lignin gives hardness.
  • Medium : Commercial fibres = sclerenchyma fibres.
  • Exam-type (CET) : Sclereids arise by thickening of parenchyma.
Remember

P living filler; C living flexible; S dead hard.

Common mistake and CET trap

‘Collenchyma is dead’ is wrong. Trap: ‘sclerenchyma has nucleus and vacuole’ is wrong.

Shortcut

Memory clue : "P-C-S: Plenty-space, Corner-thick, Stone-hard".

Spot the difference

TissueCellSupport
ParenchymaLiving, spacesLittle
CollenchymaLiving, corner-thickFlexible
SclerenchymaDead, ligninRigid

Practice questions

Easy
  1. 1Two groups of permanent tissue.
  2. 2Two functions of parenchyma.
  3. 3Collenchyma supports?
Medium
  1. 4Sclerenchyma is hard due to?
  2. 5Two examples of fibres.
  3. 6Is collenchyma in monocots?
Challenging
  1. 7Fibres vs sclereids.
  2. 8How does parenchyma form cambium?
Show answers (try them yourself first)
  1. 1Simple and complex.
  2. 2Food storage; photosynthesis.
  3. 3Young stems, leaf petiole.
  4. 4Lignin.
  5. 5Jute and flax.
  6. 6Usually absent.
  7. 7Fibres long, tapering; sclereids short, broad.
  8. 8Dedifferentiation (regains division).

Complex permanent tissue: xylem

From daily life

Like a city water pipeline, xylem carries water and minerals from root to leaf; the pipe is made of dead cells.

Simple definition

Complex tissue = more than one cell type acting as one unit. Xylem (hadrome) = water- and mineral-conducting, mostly dead tissue: tracheids, vessels, xylem parenchyma, xylem fibres.

Xylem and thickeningXylem = dead complex tissue (hadrome)Tracheiddead; 95% wood (gymno)Vesseldead; wide, angioParenchymaliving; storageFibredead; supportThickening patterns on tracheidsAnnularSpiralScalariformReticulatePittedProtoxylem = formed first, small (annular/spiral)Metaxylem = formed later, larger (reticulate/pitted)Endarch (stem): protoxylem towards pithExarch (root): protoxylem towards periphery

In the figure : Xylem components and thickening patterns of tracheids.

Rule 1 : Components of xylem — Tracheids: long, dead, oblique ends; 95% of gymnosperm wood, 5% of angiosperm. Vessels: wider than tracheids, end walls dissolved into a tube; angiosperms. Xylem parenchyma: the only living part; stores starch; lateral conduction. Xylem fibres: dead, lignified; mechanical support.

  • Easy : Gymnosperms = tracheids; angiosperms = vessels.
  • Medium : Only parenchyma is living in xylem.
  • Exam-type (CET) : Vessel = many dead members joined.

Rule 2 : Thickening, protoxylem and endarch/exarch — Wall thickening: annular (rings), spiral, scalariform (ladder), reticulate, pitted (most advanced). Protoxylem = formed first, small; metaxylem = formed later, larger. Endarch = protoxylem towards pith (stem); exarch = towards periphery (root).

  • Easy : Annular → spiral → scalariform → reticulate → pitted.
  • Medium : Stem = endarch; root = exarch.
  • Exam-type (CET) : Protoxylem small, metaxylem larger.
Remember

Xylem = dead pipe; only parenchyma is alive; stem endarch, root exarch.

Common mistake and CET trap

‘Xylem conducts food’ is wrong (water + minerals). Trap: ‘angiosperms have only tracheids’ is wrong.

Shortcut

Memory clue : "X-ylem = water eXpress up; EnDarch = pith (Inner Door)".

Spot the difference

ComponentLiving/DeadRole
TracheidDeadConduction + support
VesselDeadConduction
Xylem parenchymaLivingStorage
Xylem fibreDeadSupport

Practice questions

Easy
  1. 1What is complex tissue?
  2. 2Four components of xylem.
  3. 3Living component of xylem?
Medium
  1. 4Who conducts in gymnosperms?
  2. 5What is annular thickening?
  3. 6Example of endarch.
Challenging
  1. 7Tracheid vs vessel.
  2. 8Protoxylem vs metaxylem.
Show answers (try them yourself first)
  1. 1A tissue of more than one cell type working together.
  2. 2Tracheid, vessel, parenchyma, fibre.
  3. 3Xylem parenchyma.
  4. 4Tracheids.
  5. 5Ring-like wall thickening.
  6. 6Stem.
  7. 7Vessel wider with dissolved ends; tracheid narrow and tapering.
  8. 8Earlier/later; small/large; annular-spiral/pitted.

Phloem, epidermal and ground tissue systems

From daily life

Food made in leaves is distributed to fruits, roots and shoots; this food channel is the phloem.

Simple definition

Phloem (bast, leptome) = living tissue that conducts organic food: sieve tubes, companion cells, phloem parenchyma, phloem fibres. Tissue systems: epidermal, ground, vascular.

Phloem and stomataPhloem (bast, leptome)Sieve tube(no nucleus)CompanioncellSieve plate = poresPhloem parenchyma, fibres (dead)Stomatal apparatuspore2 guard cells (dicot: kidney)+ subsidiary cellsmonocot: dumbbellEpidermis: outer layer; cuticle saves waterRoot hairs absorb; stem has trichomesGround tissue = all except epidermis and vascularVascular system = xylem + phloem

In the figure : Structure of phloem and the stomatal apparatus.

Rule 1 : Components of phloem — Sieve tubes: living tubes joined end to end; sieve plates with pores; no nucleus when mature. Companion cells: nucleus and dense cytoplasm; control the sieve tube; both arise from one cell. Phloem parenchyma: stores food, latex (absent in most monocots). Phloem fibres: dead; ropes. Sieve cells: pteridophytes and gymnosperms.

  • Easy : Phloem is living (only fibres are dead).
  • Medium : Sieve tube + companion cell are a pair; if one dies, so does the other.
  • Exam-type (CET) : Phloem: proto (first) and meta (later).

Rule 2 : Epidermal and ground tissue systems — Epidermis: single outer layer, no gaps; cuticle saves water; root hairs in roots absorb; trichomes on stems. Stoma = pore with two guard cells (dicot: kidney; monocot: dumbbell) + subsidiary cells. Ground tissue = everything except epidermis and vascular tissue (cortex, pith, mesophyll).

  • Easy : Guard cells change turgor to open/close the stoma.
  • Medium : Stomatal apparatus = stoma + guard + subsidiary cells.
  • Exam-type (CET) : Root hair = unicellular; trichome = multicellular.
Remember

Phloem = living food channel; guard cells = doors of the stoma.

Common mistake and CET trap

‘Sieve tube has a nucleus’ is wrong. Trap: ‘phloem carries water’ is wrong (food).

Shortcut

Memory clue : "Phloem = Plant food; sieve plate = a strainer".

Spot the difference

ComponentNatureRole
Sieve tubeLiving, no nucleusFood conduction
Companion cellLiving, nucleusRegulation
Phloem fibreDeadSupport

Practice questions

Easy
  1. 1Other name for phloem?
  2. 2What does phloem carry?
  3. 3Dead part of phloem?
Medium
  1. 4What is a sieve plate?
  2. 5Function of cuticle?
  3. 6Trichome vs root hair.
Challenging
  1. 7Shape of guard cells?
  2. 8What is ground tissue?
Show answers (try them yourself first)
  1. 1Bast / leptome.
  2. 2Organic food (source → sink).
  3. 3Phloem fibres.
  4. 4Pore-bearing end wall.
  5. 5Reduces water loss.
  6. 6Trichome multicellular on stem; root hair unicellular on root.
  7. 7Dicot: kidney; monocot: dumbbell.
  8. 8All tissue except epidermis and vascular tissue.

Vascular bundles and secondary growth

From daily life

Pipes can run together or separately; the way xylem and phloem sit decides the type of vascular bundle.

Simple definition

Vascular bundle = a group of xylem and phloem. Secondary growth = girth increase by cambium in dicots and gymnosperms. Intrafascicular + interfascicular cambium = cambial ring.

Vascular bundles and secondary growthTypes of vascular bundlesRadialrootCollateralopen (cambium)CollateralclosedBicollateralCucurbitaceaeLeptocentricphloem insideHadrocentricxylem inside■ xylem■ phloem▬ cambiumSecondary growth (dicot stem)Intrafascicular + interfascicular cambium = cambial ringRing cuts inward → secondary xylem; outward → secondary phloemMore xylem than phloem formsMonocots: no cambium → no girth growth (exception: anomalous)

In the figure : Types of vascular bundles and the sequence of secondary growth.

Rule 1 : Types of vascular bundles — Radial: xylem and phloem on separate radii (root). Conjoint collateral: on the same radius, xylem inside, phloem outside (stem); open = cambium present; closed = absent. Bicollateral: phloem on both sides (Cucurbitaceae). Concentric: leptocentric (phloem inside), hadrocentric (xylem inside). Amphicribral / amphivasal.

  • Easy : Open = secondary growth possible; closed = not.
  • Medium : Radial = root; collateral = stem.
  • Exam-type (CET) : Concentric bundles are always closed.

Rule 2 : Secondary growth — Primary growth = length by apical meristem. In a dicot stem: intrafascicular cambium + dedifferentiated medullary ray cells → interfascicular cambium → cambial ring. The ring forms secondary xylem inward and secondary phloem outward; more xylem. Monocots lack cambium; exceptions: Dracaena, Agave (anomalous).

  • Easy : Dedifferentiation = permanent cells regain division.
  • Medium : More secondary xylem = wood.
  • Exam-type (CET) : Gymnosperms also show secondary growth.
Remember

Open = cambium = grows thicker; closed = does not.

Common mistake and CET trap

‘Monocot stem has cambium’ is wrong. Trap: ‘radial bundle in stem’ is wrong (root).

Shortcut

Memory clue : "Open = Operates cambium; Closed = Cannot grow".

Spot the difference

TypeExampleCambium
RadialRoot—
Collateral openDicot stemYes
Collateral closedMonocot stemNo

Practice questions

Easy
  1. 1Where is radial bundle?
  2. 2Conjoint collateral means?
  3. 3What is in an open bundle?
Medium
  1. 4Bicollateral occurs in?
  2. 5What is leptocentric?
  3. 6How does a cambial ring form?
Challenging
  1. 7Why is secondary xylem more?
  2. 8Why no secondary growth in monocots?
Show answers (try them yourself first)
  1. 1In roots.
  2. 2Xylem and phloem on the same radius.
  3. 3Cambium.
  4. 4Cucurbitaceae.
  5. 5Phloem inside, xylem outside.
  6. 6Intra- and interfascicular cambium join.
  7. 7Cambium cuts more cells inward.
  8. 8No cambium; bundles are closed.

Wood, cork cambium and periderm

From daily life

Look at a cut tree trunk: dark centre, lighter outside, rings and bark on top – all evidence of years of secondary growth.

Simple definition

Wood = secondary xylem. Phellogen (cork cambium) forms phellem (cork) outside and phelloderm inside; together they are the periderm.

Wood and peridermHeartwood (duramen): dead, tyloses, durableSapwood (alburnum): conducts sapCambium ringBark / cork: protectionAnnual ring: spring wood + autumn woodSpring: wide lumen, light, few fibresAutumn: narrow, dark, many fibresPeriderm = phellogen + phellem + phellodermPhellem (cork) outsidePhellogen (cork cambium)Phelloderm insideLenticels = aerating pores on the barkCork: suberin makes it waterproof

In the figure : Section of a trunk: heartwood, sapwood, cambium, bark and periderm.

Rule 1 : Wood: annual rings, heartwood, sapwood — In favourable seasons spring wood forms: wide lumen, thin wall, light colour, few fibres. In unfavourable seasons autumn wood: narrow, dark, thick walls, many fibres. Together they form one annual ring (clear in cold places like Kashmir). Heartwood: plugged by tyloses, oils and tannins, dead, durable; sapwood: living, conducts sap.

  • Easy : One ring = one year (spring + autumn).
  • Medium : Durable heartwood is used for furniture.
  • Exam-type (CET) : Tyloses plug the xylem tubes.

Rule 2 : Cork cambium, periderm and bark — When the epidermis ruptures, outer cortex cells become meristematic as phellogen. Outside: cork (phellem), waterproof due to suberin; inside: phelloderm (secondary cortex). Bark = everything outside the vascular cambium. Lenticels = gas-exchange pores in the bark. Roots too show secondary growth.

  • Easy : Periderm = phellogen + phellem + phelloderm.
  • Medium : Cork is dead; suberin makes it waterproof.
  • Exam-type (CET) : Bark is a non-technical term for all outer tissues.
Remember

Spring = wide light; autumn = narrow dark; periderm = P-P-P.

Common mistake and CET trap

‘Phellem forms inside’ is wrong (outside). Trap: ‘heartwood is living’ is wrong.

Shortcut

Memory clue : "Phellem = Perimeter (outside); Phelloderm = Deep (inside)".

Spot the difference

PointSpring woodAutumn wood
LumenWideNarrow
ColourLightDark
DensityLowHigh

Practice questions

Easy
  1. 1What forms an annual ring?
  2. 2Other name for heartwood?
  3. 3Function of sapwood?
Medium
  1. 4What are tyloses?
  2. 5Job of phellogen?
  3. 6What is a lenticel?
Challenging
  1. 7Why faint rings in Maharashtra?
  2. 8Why is cork waterproof?
Show answers (try them yourself first)
  1. 1Spring and autumn wood.
  2. 2Duramen.
  3. 3Conducting sap.
  4. 4Parenchyma outgrowths that plug xylem tubes.
  5. 5Forms cork and phelloderm.
  6. 6Gas-exchange pore on bark.
  7. 7Less seasonal difference.
  8. 8Due to suberin.

Anatomy of root, stem and leaf

From daily life

Under the microscope a section is identified like a puzzle: bundles in a ring = dicot; scattered = monocot.

Simple definition

Anatomy = internal structure. T.S. of root, stem and leaf differs in dicots and monocots; leaf: dorsiventral (dicot) and isobilateral (monocot).

Root, stem and leaf anatomyDicot stemMonocot stemLeaf (dorsiventral)pithbundles scatteredring, openStomata mostly belowDicot root2–6 xylem, exarch; small pith; Casparian stripMonocot rootMore than 6 xylem (polyarch); large pithDicot stemHypodermis collenchyma; pith present; openMonocot stemHypodermis sclerenchyma; no pith; closedMonocot leafisobilateral; stomata both sides; bulliform cells

In the figure : Dicot and monocot stems, leaf layers and a root-stem-leaf comparison.

Rule 1 : Root and stem — Dicot root: epiblema (root hairs) → cortex → exodermis → endodermis (Casparian strip, passage cells) → pericycle → stele; 2–6 xylem, exarch; small pith; later secondary growth. Monocot root: more than 6 xylem (polyarch); large pith; no secondary growth. Dicot stem: epidermis (trichomes), collenchymatous hypodermis, cortex, endodermis (starch sheath), pericycle (hard bast), bundles in a ring, collateral open, endarch; pith present. Monocot stem: sclerenchymatous hypodermis; scattered closed bundles with bundle sheath; no pith; lysigenous cavity.

  • Easy : Endodermis: Casparian strip (suberin) regulates water.
  • Medium : Root is exarch; stem is endarch.
  • Exam-type (CET) : Monocot stem: scattered closed bundles.

Rule 2 : Leaf — Dorsiventral (dicot): upper epidermis (few stomata) → palisade (long, many chloroplasts) → spongy (loose, spaces) → lower epidermis (more stomata, sub-stomatal chamber). Bundles closed; xylem above, phloem below; bundle sheath. Isobilateral (monocot): stomata on both sides; mesophyll not differentiated; parallel veins; bulliform cells help rolling.

  • Easy : No cambium in leaves → no secondary growth.
  • Medium : Palisade is above and makes food.
  • Exam-type (CET) : Amphistomatic = stomata on both surfaces.
Remember

Dicot = ring, pith; monocot = scattered, no pith; root polyarch > 6.

Common mistake and CET trap

‘Monocot stem has cambium’ is wrong. Trap: ‘dicot leaf stomata only above’ is wrong (more below).

Shortcut

Memory clue : "Mono = Many scattered; Di = Disciplined ring".

Spot the difference

PointDicotMonocot
Stem bundlesRing, openScattered, closed
Root xylem2–6More than 6
LeafDorsiventralIsobilateral

Practice questions

Easy
  1. 1What is epiblema?
  2. 2Casparian strip is made of?
  3. 3What is polyarch?
Medium
  1. 4Bundles in dicot stem?
  2. 5Is there pith in monocot stem?
  3. 6Where is palisade parenchyma?
Challenging
  1. 7Function of bulliform cells?
  2. 8Dicot vs monocot leaf.
Show answers (try them yourself first)
  1. 1Outermost root layer with root hairs.
  2. 2Suberin; in endodermal walls.
  3. 3More than six xylem groups (monocot root).
  4. 4Ring, conjoint, collateral, open, endarch.
  5. 5No.
  6. 6Below upper epidermis.
  7. 7Help leaf rolling.
  8. 8Dorsiventral/isobilateral; stomata mostly below/both; palisade-spongy/none.

Quick revision of the whole lesson

ConceptKey fact
MeristemApical = length; lateral = girth
Simple tissuesP living; C living; S dead (lignin)
XylemDead; water; tracheid, vessel; endarch/exarch
PhloemLiving; food; sieve tube + companion
BundlesRadial; collateral open/closed; concentric
Secondary growthCambial ring; periderm = P-P-P
AnatomyDicot ring; monocot scattered

🎯 Most important points for the exam

  • Classification of meristems.
  • Parenchyma, collenchyma, sclerenchyma comparison.
  • Xylem vs phloem.
  • Types of vascular bundles.
  • Secondary growth, annual ring, periderm.
  • T.S. of dicot/monocot root, stem, leaf.
Study mantra

Understand the concept → draw the figure → memorise the key points → solve questions yourself.