Root, Stem and Leaves

📚

TISSUE SYSTEM

📖

Epidermal tissue system

▢ Definition: Outer covering of plants

▢ Includes:

Epidermis
Stomata
Trichomes / hairs

📝

Epidermis

Root	Stem	Leaves

▢ Definition: Epi = upon; derma = skin → continuous outer layer interrupted by stomata + lenticels

▢ Layering:

Table 1: Epidermis layering

Type	Occurrence / Example
Generally	Single-layered
Multilayered epidermis	Phylloclades of Casuarina; leaves of Nerium + Ficus; hygroscopic roots of epiphytes
Velamen	Multiple epidermis on hygroscopic roots; cells dead

▢ Cuticle:

•
Present on epidermis of stem + leaves
•
Absent in root
•
Protection to epidermis
•
Checks excessive transpiration

▢ Chloroplast:

•
Epidermal cells living
•
Generally no chloroplast
•
Exceptions → shade plants / sciophytes, hydrophytes, some ferns
•
Guard cells contain chloroplast
•
Guard cells living but heteromorphic due to absence of RUBISCO

▢ Special Epidermal Cells / Contents:

Table 1: Special epidermal points

Structure / Content	Occurrence	Function / Note
Bulliform / motor / bubble-like cells	Upper epidermis of isobilateral leaves / monocots	Rolling + unrolling of leaves; mainly rolling
Epiblema / piliferous layer / rhizodermis	Outermost layer of root	Not cutinised/suberised; no stomata
Stomata + lenticels	Epidermis	Confined to epidermis
Silica	Epidermal cells of grasses + Equisetum	Mechanical strength
Lithocysts	Epidermal cells containing cystoliths	Cystolith = \(CaCO_3\)

📝

Stomata

▢ Definition: Minute pores on epidermal surface of leaves + some herbaceous stems

▢ Structure:

•
Each stoma guarded by 2 guard cells
•
Guard cells = specialized epidermal cells
•
Subsidiary / accessory cells surround guard cells

▢ Guard Cell Shape:

Table 1: Guard cell shape

Plant group	Guard cell shape
Dicots	Kidney-shaped / bean-shaped
Some monocots e.g., doob grass / Cynodon dactylon, maize	Dumb-bell / barbell-shaped

▢ Distribution:

Table 1: Stomatal distribution

Plant / Leaf type	Stomata distribution
Dicot leaves	Scattered; generally lower epidermis
Monocot leaves	Scattered in rows; both surfaces
Free-floating hydrophytes e.g., lotus, Nymphaea	Upper epidermis
Submerged hydrophytes	Absent / non-functional
Algae + fungi	Totally absent

▢ Leaves Based on Stomata:

Table 1: Leaves by stomatal distribution

Leaf type	Stomata found on	Examples
Epistomatic	Upper surface	Free-floating hydrophytes e.g., lotus, Nymphaea
Hypostomatic	Lower surface	Common dicot leaves
Amphistomatic	Both surfaces	Common monocot leaves

📝

Trichome / Hairs

Table 1: Trichomes

Type	Occurrence	Function
Unicellular	Roots	Absorption / protection
Multicellular	Stems	Checks excess water loss + protection

📖

Ground tissue system

▢ Definition: Tissue system between epidermis and vascular tissue

▢ Components:

Hypodermis
Cortex
Endodermis
Pericycle
Medulla / pith
Medullary rays / pith rays
Conjunctive tissue

📝

Hypodermis

Table 1: Hypodermis

Point	Data
Position	Outermost layer of cortex
Herbaceous dicot stem	Collenchymatous
Monocot stem	Sclerenchymatous

📝

Cortex

•
Present inside hypodermis
•
Usually parenchymatous
•
Abundant intercellular space
•
Innermost layer → endodermis

📝

Endodermis / Starch Sheath

▢ Definition: Single-layered tissue separating cortex from stele

▢ System: Part of extrastelar ground tissue system

▢ Cell Features:

•
Barrel-shaped
•
No intercellular spaces
•
Living
•
Starch-containing → starch sheath

▢ Casparian Strips:

•
Radial + tangential wall thickening; mainly radial wall
•
Made of lignin + suberin + cutin
•
Stripes/bands → Casparian strips / Casparian bands
•
Casparian strips + passage cells also found in exodermis

▢ Passage Cells:

•
Present just against protoxylem in root
•
Exodermis may occur in some roots e.g., hygroscopic roots of epiphytes

▢ Root Point: Well-developed endodermis = constant feature of roots; not constant in stem

📝

Pericycle

▢ Position: Inside endodermis

▢ Layers: Single-layered or few-layered

▢ Cell Type: Thin-walled parenchymatous or rarely thick-walled sclerenchymatous

▢ Occurrence:

•
Present in most roots
•
Absent in roots of parasitic plants + hydrophytes

▢ Special Cases:

Table 1: Pericycle special cases

Plant / Case	Pericycle feature
Smilax root / monocot	Multilayered + sclerenchymatous
Sunflower stem	Heterogeneous → thick-walled + thin-walled cells

▢ Functions:

Table 1: Pericycle functions

Pericycle type	Function
Thick-walled	Mechanical
Thin-walled	Storage
Dicot root pericycle	Can form cambium

📝

Medulla / Pith and Medullary Rays

▢ Definitions:

Table 1: Pith and pith rays

Term	Meaning
Medulla / pith	Core of plant axis occupied by parenchymatous tissue
Medullary rays / pith rays	Pith radiating between vascular bundles

▢ Functions:

Table 1: Functions

Structure	Function
Pith	Food storage
Medullary rays	Lateral transportation

▢ Distribution:

Table 1: Pith distribution

Plant part	Pith status
Dicot stem	Distinct / developed
Monocot root	Distinct / developed
Monocot stem	Scattered
Dicot root	Indistinct / small / absent
Triticum stem	Central region hollow → pith cavity
Ricinus	Pith cavity among dicots

📝

Conjunctive Tissue

Parenchymatous tissue between xylem and phloem bundles

📝

Cortex and Stele

Table 1: Cortex vs stele

Region	Meaning
Cortex	Ground tissue outside endodermis
Stele	All tissues inside endodermis
Monocot stele	Atactostele
Dicot stele	Eustele

Endodermis absent in monocot stem → ground tissue not differentiated into cortex and stele

📝

MCQ Point

📖

Vascular tissue system

▢ Definition:

•
Central column of root/stem axis = stele
•
Stele made of vascular bundles
•
Stelar region includes all tissues inside pericycle
•
Vascular bundle = xylem + phloem + cambium if present
•
Cambium = strip of primary meristem

▢ Types of Vascular Bundles:

❖ Radial:

•
Xylem + phloem in separate bundles
•
Present on different radii
•
Alternate arrangement
•
Equal in number
•
Example → roots of dicots + monocots

❖ Conjoint:

▢ Definition: Xylem + phloem in same bundle and same radius

▢ Example: Stem

▢ Types:

❖ Collateral:

Table 1: Collateral vascular bundle

Type	Cambium	Example / Note
Open collateral	Present between xylem + phloem	Dicot stem; conjoint, collateral, open
Closed collateral	Absent	Monocot stem; conjoint, collateral, closed

Phloem outside/pericycle side; xylem towards centre/pith

❖ Bicollateral:

▢ Definition: Phloem present on both sides of xylem

▢ Bundle Nature: Always open

▢ Arrangement: Phloem → cambium → xylem → cambium → phloem

▢ Examples:

•
Stem of Cucurbitaceae
•
Stem of Solanaceae
•
Stem of Convolvulaceae

▢ MCQ Point:

❖ Concentric:

▢ Definition: Xylem + phloem arranged in definite circle

▢ Nature: Always closed

▢ Occurrence: Characteristic of pteridophytes + few monocots

▢ Types:

Table 1: Concentric vascular bundles

Type	Arrangement	Examples
Amphicribal / hadrocentric	Xylem central; phloem surrounds xylem	Ferns, some aquatic angiosperms, Lycopodium, Selaginella
Amphivasal / leptocentric	Phloem central; xylem surrounds phloem	Underground stem of some monocots e.g., dagger plant / Yucca, dragon plant / Dracaena, sweet flag / Acorus

📚

ROOT-STEM TRANSITION

•
Conversion: radial + exarch vascular bundle → conjoint + endarch vascular bundle
•
Xylem swings during transition
•
Phloem remains stationary
•
Transition zone present in hypocotyl

📚

ORIGIN OF LATERAL ROOTS AND LATERAL BRANCHES OF STEM

Table 1: Origin of lateral organs

Structure	Origin	Source / Seat
Lateral root	Endogenous	Pericycle
Seat of lateral root origin	Just against protoxylem	Pericycle opposite protoxylem
Lateral branch of stem	Exogenous	Outer part of cortex

📚

ANATOMY OF STEM

▢ Dicot Stem vs Monocot Stem:

Table 1: Anatomy of dicot and monocot stem

Feature	Dicot stem	Monocot stem

Epidermis	Epidermis with multicellular hairs + stomata with kidney-shaped guard cells	Outer epidermis cutinized; stomata with dumb-bell-shaped guard cells
Hypodermis	Collenchymatous	Sclerenchymatous
Internal tissue arrangement	Concentric	Concentric arrangement absent
Ground tissue	Differentiated into hypodermis, general cortex, endodermis, pericycle, pith	Not differentiated
Stem centre	Almost always solid	Usually hollow centre; exception maize
Vascular bundle arrangement	Ring around pith	Scattered throughout ground tissue
Vascular bundle number/size	Few + similar size	Numerous; smaller at periphery, larger towards central axis
Vascular bundle type	Conjoint, collateral, open	Conjoint, collateral, closed
Bundle sheath	Absent	Sclerenchymatous bundle sheath present
Bundle outline	Wedge-shaped	Oval / rounded
Phloem parenchyma	Present	Absent
Protoxylem cavity	Absent	Present; exception Asparagus
Vessel arrangement	Rows/chains; linear fashion	Y-shaped manner
Stele	Eustele / dictyostele	Atactostele; most advanced stele
Pericycle	Alternating zones of parenchyma + sclerenchyma	Mostly absent
Medullary rays	Present	Absent
Secondary growth	Present	Absent

📚

ANATOMY OF ROOT

▢ Common Features of Dicot and Monocot Roots:

•
Wide cortex made of thin-walled cells
•
Vascular bundle radial
•
Xylem exarch
•
Distinct endodermis + passage cells
•
Lateral roots arise opposite protoxylem points from pericycle → endogenous

▢ Dicot Root vs Monocot Root:

Table 1: Anatomy of dicot and monocot root

Feature	Dicot root	Monocot root

Cortex	Narrow	Very wide
Outer tissues during secondary growth	Epiblema, cortex, endodermis peeled off and replaced by cork	Cork not formed; only epiblema peeled off; cortex + endodermis persist
Endodermis	Less thickened; Casparian strips prominent	Casparian strips visible only in young roots; later endodermal cells highly thickened
Passage cells	Generally absent	Generally present in endodermis opposite protoxylem
Pericycle produces	Lateral roots + cork cambium + vascular cambium	Lateral roots only
Xylem and phloem bundles	Diarch to hexarch / \(2-6\)	Polyarch / \(>8\)
Conjunctive tissue	Parenchymatous	Parenchymatous or sclerenchymatous
Conjunctive parenchyma	Forms cambium	Does not form cambium
Pith	Small or absent	Well-developed
Protoxylem and metaxylem	Linear fashion	Linear or V-shaped
Secondary growth	Present	Absent

▢ Special Points:

•
Grafting not possible in monocots → cambium absent
•
Girdling not possible due to scattered vascular bundles

📚

HISTOLOGY OF LEAF

▢ General Points:

•
Dicot leaf horizontal; upper sun-facing part darker → dorsiventral leaf
•
Monocot leaf nearly vertical; both surfaces equally exposed → isobilateral leaf
•
Leaf anatomy → upper epidermis + lower epidermis + mesophyll + vascular bundle
•
Inverted vascular bundle → xylem upper side, phloem lower side

▢ Vascular Bundle:

•
Conjoint
•
Collateral
•
Mesarch xylem

▢ Dicot Leaf vs Monocot Leaf:

Table 1: Histology of dicot and monocot leaf

Feature	Dicot leaf	Monocot leaf

Cuticle thickness	Upper epidermis thicker than lower epidermis	Same in both epidermis
Bulliform / motor cells	Absent	Present
Number of stomata	Greater on lower surface than upper	Equal on both surfaces
Guard cells	Kidney-shaped	Dumb-bell-shaped
Mesophyll	Differentiated into upper tightly packed palisade parenchyma + lower loosely arranged spongy parenchyma	Not differentiated into palisade and spongy parenchyma
Bundle sheath extension	Present in larger veins; parenchymatous	Present; sclerenchymatous
Bundle sheath cells	Colourless
Lysigenous cavity in xylem	Absent	Usually present

Q1.

Plasmolysis in plant cells occur when they are placed in: [IOM 1998]

📅IOM 1998

Q2.

Fertilizers can kill plants due to: [IOM 1996]

📅IOM 1996

Q3.

When the fluid outside a cell has greater concentration of a given molecule than the fluid inside the cell, the external fluid is: [BPKIHS 2004]

📅BPKIHS 2004

Q4.

The process of imbibition can be noticed when: [BPKIHS 2004]

📅BPKIHS 2004

Q5.

An Amoeba survives in a hypotonic solution that destroys a human RBC. It is due to [BPKIHS 2004]

📅BPKIHS 2004

Q6.

Imbibition demonstrates the process of: [BPKIHS 2006]

📅BPKIHS 2006

Q7.

When a cell is fully turgid its: [BPKIHS 1997]

📅BPKIHS 1997

Q8.

The turgidity of the cell is maintained by: [MOE 2008]

📅MOE 2008

Q9.

Plasmolysis is defined as: [MOE 2063]

📅MOE 2063

Q10.

Selective permeability identifies the process of: [MOE 2062]

📅MOE 2062

Q11.

Imbibition theory for ascent of sap was given by: [MOE 2000]

📅MOE 2000

Q12.

Plant absorb water by: [MOE 2065]

📅MOE 2065

Q13.

Transpiration is high during following condition: [IOM 2007]

📅IOM 2007

Q14.

Potometer is used to measure: [IOM 2006]

📅IOM 2006

Q15.

Out of water absorbed by plants, water actually used by them is: [IOM 1997]

📅IOM 1997

Q16.

Opening of the stomata is because of: [IOM 1997]

📅IOM 1997

Q17.

K+ exchange theory is concerned with: [IOM 1997]

📅IOM 1997

Q18.

Transpiration is highest for ……… transpiration: [IOM 1996]

📅IOM 1996

Q19.

Loss of water in the form of vapour from the living tissue of aerial parts of the plant is termed as: [BPKIHS 2006]

📅BPKIHS 2006

Q20.

Rate of transpiration is affected by humidity in: [BPKIHS 2000]

📅BPKIHS 2000

Q21.

The pores specialized for guttation in plants are called: [BPKIHS 2001]

📅BPKIHS 2001

Q22.

Cells in the root having power of division: [BPKIHS 2003]

📅BPKIHS 2003

Q23.

Which one keeps its stomata open during night and closed during day? [BPKIHS 2004]

📅BPKIHS 2004

Q24.

The rate of transpiration during storm is [BPKIHS 1995]

📅BPKIHS 1995

Q25.

There is accumulation of water drops at the leaf margin of Colocasia early in the morning, this is the result of [BPKIHS 1996]

📅BPKIHS 1996

Q26.

If a plant kept in air free of CO_2 [BPKIHS 1998]

📅BPKIHS 1998

Q27.

The translocation of food in plants occurs in the form of: [IE 2001]

📅IE 2001

Q28.

Who proposed the 'Cohesion-Tension' and 'Transpiration pull theory'? [MOE 2062]

📅MOE 2062

Q29.

Root pressure is maximum when: [MOE 2062]

📅MOE 2062

Q30.

The nature of dry cobalt chloride paper which is used in transpiration is: [MOE 2058]

📅MOE 2058

Q31.

Minute pore-like opening found in cork that help in exchange of gases are called: [MOE 2052]

📅MOE 2052

Q32.

The region just behind the root apex is: [MOE 2061]

📅MOE 2061

Q33.

The maximum amount of solute present in the phloem sap is: [IE 2002]

📅IE 2002

Q34.

In roots, the tissue which helps in the absorption of water and minerals is: [IE 2002]

📅IE 2002

Q35.

Root tip is more distant than any other apical part of plant due to: [IE 2005]

📅IE 2005

Q36.

The lowest water potential in the xylem are in the: [IE 2007]

📅IE 2007

Q37.

Cell wall enlarges if kept in: [IE 2008]

📅IE 2008

Q38.

Chlorophyll contains which metal ion: [IE 2008]

📅IE 2008

Q39.

A micronutrient absorbed by foliage is [IE 2009]

📅IE 2009

Q40.

The immediate effect of destruction of ATP inside cell is in [BPKIHS 2016]

📅BPKIHS 2016

Q41.

When a plant cell is kept in water, water continues to move inside until the [BPKIHS 2016]

📅BPKIHS 2016

Q42.

Bacteria can't grow in honey because [BPKIHS 2016]

📅BPKIHS 2016

Q43.

Common disease caused due to deficiency of P, K, Mg, Mn, Ca "and" N is [BPKIHS 2014]

📅BPKIHS 2014

Q44.

Which of the following becomes difficult in absence of ATP? [BPKIHS 2012]

📅BPKIHS 2012

Q45.

Which of the following factors does not affect osmosis? [BPKIHS 2010]

📅BPKIHS 2010

Q46.

The device which is used to nullify the effect of gravity is called [IOM 2014]

📅IOM 2014

Q47.

Plasmolysis is caused when cell is placed in [IOM 2016]

📅IOM 2016

Q48.

Site of evaporation of water is [IOM 2012]

📅IOM 2012

Q49.

For plasmolysis, cell is placed in [IOM 2012]

📅IOM 2012

Q50.

The cell becomes turgid when placed in [MOE 2014]

📅MOE 2014

Q51.

Ascent of sap in plants is due to [MOE 2014]

📅MOE 2014

Q52.

Guttation is the manifestation of [MOE 2012]

📅MOE 2012

13Root, Stem and Leaves

Table 1: Epidermis layering

Table 1: Special epidermal points

Table 1: Guard cell shape

Table 1: Stomatal distribution

Table 1: Leaves by stomatal distribution

Table 1: Trichomes

Table 1: Hypodermis

Table 1: Pericycle special cases

Table 1: Pericycle functions

Table 1: Pith and pith rays

Table 1: Functions

Table 1: Pith distribution

Table 1: Cortex vs stele

Table 1: Collateral vascular bundle

Table 1: Concentric vascular bundles

Table 1: Origin of lateral organs

Table 1: Anatomy of dicot and monocot stem

Table 1: Anatomy of dicot and monocot root

Table 1: Histology of dicot and monocot leaf

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