plant tissues & organs

B IBIBIBIO 101 Labo ra t o ryO 101 Labo ra t o ryO 101 Labo ra t o ryO 101 Labo ra t o ry Th i s s e rv es a s a su pp l em en t in th e l a bo ra to ry .Th i s s e rv es a s a su pp l em en t in th e l a bo ra to ry .Th i s s e rv es a s a su pp l em en t in th e l a bo ra to ry .Th i s s e rv es a s a su pp l em en t in th e l a bo ra to ry .

Don ’ t Don ’ t Don ’ t Don ’ t u s e th i s i n y ou r l e c tu r e c l a s s .u s e th i s i n y ou r l e c tu r e c l a s s .u s e th i s i n y ou r l e c tu r e c l a s s .u s e th i s i n y ou r l e c tu r e c l a s s .

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EXERCISE VIIEXERCISE VIIEXERCISE VIIEXERCISE VII PLANT TISSUESPLANT TISSUESPLANT TISSUESPLANT TISSUES

A. MERISTIMATIC TISSUES / MERISTEMSA. MERISTIMATIC TISSUES / MERISTEMSA. MERISTIMATIC TISSUES / MERISTEMSA. MERISTIMATIC TISSUES / MERISTEMS

� composed of mitotically dividing cells � responsible for elongation & widening the diameter of plant organs 1. Apical MeristemApical MeristemApical MeristemApical Meristem

� found at the tips of stems (shoot apical meristem) & roots (root apical meristem); produce primary tissues

� account for primary growth → elongation of roots & shoots

Root Apical MeristemRoot Apical MeristemRoot Apical MeristemRoot Apical Meristem

(RAM)

Shoot Apical MeristemShoot Apical MeristemShoot Apical MeristemShoot Apical Meristem

(SAM)

2. Intercalary MeristemIntercalary MeristemIntercalary MeristemIntercalary Meristem � occur between mature tissues � most common in grasses → occur at the bases of the nodes

� help regenerate parts removed by grazing herbivores � for rapid elongation of the internodes in monocots

3. Lateral MeristemLateral MeristemLateral MeristemLateral Meristem

� cylindrical meristems that form the subapical regions of the roots & shoots of woody plants � produce secondary growth → increases the girth of the plant

� secondary growth makes the plant sturdier enabling it to grow taller & intercept light � it includes the vascular cambium & cork cambium (also, phellogen) � vascular cambiumvascular cambiumvascular cambiumvascular cambium → forms the wood (secondary xylem) & secondary phloem

� cork cambiumcork cambiumcork cambiumcork cambium (phellogenphellogenphellogenphellogen) → forms the periderm which in turn forms a layer of dead, suberized cells that protects the inner tissues of the secondary plant body



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Intercalary MeristemIntercalary MeristemIntercalary MeristemIntercalary Meristem

(found only in monocots)

Lateral MeristemLateral MeristemLateral MeristemLateral Meristem

(Vascular cambium & Cork Cambium) B. PROTECTIVE TISSUESB. PROTECTIVE TISSUESB. PROTECTIVE TISSUESB. PROTECTIVE TISSUES / DERMAL TISSUES/ DERMAL TISSUES/ DERMAL TISSUES/ DERMAL TISSUES

� comprise the outermost layer of the plants 1.1.1.1. EpidermisEpidermisEpidermisEpidermis

� dermal tissue that covers the primary body of the plant, protecting the underlying tissues � regulates the movement of gases between the plant and the atmosphere � sheet of cutinized cells covering the plants to protect it against rapid water loss & mechanical injury

� modified epidermal cells: � Guard CellsGuard CellsGuard CellsGuard Cells

� kidney-shaped in dicots � dumbbell-shaped in monocots

� TrichomesTrichomesTrichomesTrichomes � single-celled or multicellular outgrowths of epidermal cells � found in leaves, stems, flowers, & fruits � e.g.: cotton fibers → from the epidermis of cotton seeds

2.2.2.2. CorkCorkCorkCork � the outermost part of the periderm � secondary tissue produced by the cork cambium

Epidermis with Guard Cells & Epidermis with Guard Cells & Epidermis with Guard Cells & Epidermis with Guard Cells &

StomaStomaStomaStomatatatata

TrichomesTrichomesTrichomesTrichomes CorkCorkCorkCork



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C. C. C. C. FUNDAMENTAL/ GROUND TISSUESFUNDAMENTAL/ GROUND TISSUESFUNDAMENTAL/ GROUND TISSUESFUNDAMENTAL/ GROUND TISSUES � more variable in function & type � it constitute the mesophyll in leaves & the cortex & pith in stems & roots 1. ParenchymaParenchymaParenchymaParenchyma

� isodiametric or polyhedral cells with prominent protoplast & thin walls � common examples are: � Chlorenchyma Chlorenchyma Chlorenchyma Chlorenchyma – contains chloroplasts � Aerenchyma Aerenchyma Aerenchyma Aerenchyma – cells with prominent intercellular spaces

2. CollenchymaCollenchymaCollenchymaCollenchyma � consists of cells with unevenly thickened cell walls � functions for support

3. SclerenchymaSclerenchymaSclerenchymaSclerenchyma � consists of cells which are devoid of protoplast upon maturity but has thick lignified walls � two types of cells: � Sclerids Sclerids Sclerids Sclerids – short & polygonal

� e.g.: stone cells in pears gives it a gritty texture (rough) � Fibers Fibers Fibers Fibers – long and with tapering ends

� e.g.: hemp fibers for making ropes

ParenchymaParenchymaParenchymaParenchyma CollenchymaCollenchymaCollenchymaCollenchyma SclerenchymaSclerenchymaSclerenchymaSclerenchyma Distinguishing

Features � made up of parenchyma cells parenchyma cells parenchyma cells parenchyma cells → usually many sided

� made up of collenchyma collenchyma collenchyma collenchyma cells cells cells cells → elongated in shape

� made up of fibers fibers fibers fibers (long slender cells typically occurring in strands) & sclerids sclerids sclerids sclerids (variable shape, shorter than fibers)

Cell Wall � primary or secondary; may be lignified, suberized, or cutinized

� alive at maturity

� unevenly thickened primary cell wall only; not lignified

� alive at maturity

� primary & thick secondary; usually lignified

� maybe alive or dead at maturity

Location on the Plant Body

� Throughout the plant body

� beneath the epidermis in young elongating stems often seen as a cylinder of tissue or only in patches in ribs along veins in some leaves

� Fibers: Fibers: Fibers: Fibers: usually associated with xylem & phloem; in leaves in monocots; sometimes in cortex of stems

� Sclerids: Sclerids: Sclerids: Sclerids: throughout the plant

Function � for metabolic processes such as respiration & photosynthesis; storage & conduction; wound healing & regeneration

� support in primary plant body

� Fibers → for support

� Sclerids → for protection & mechanical support



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Parenchyma CellsParenchyma CellsParenchyma CellsParenchyma Cells

Chollenchyma CellsChollenchyma CellsChollenchyma CellsChollenchyma Cells

Sclerenchyma CellsSclerenchyma CellsSclerenchyma CellsSclerenchyma Cells

Sclerenchyma (Fiber Cells)Sclerenchyma (Fiber Cells)Sclerenchyma (Fiber Cells)Sclerenchyma (Fiber Cells)

Sclerenchyma (Stone Cells)Sclerenchyma (Stone Cells)Sclerenchyma (Stone Cells)Sclerenchyma (Stone Cells)

D. Vascular / Conducting TissuesD. Vascular / Conducting TissuesD. Vascular / Conducting TissuesD. Vascular / Conducting Tissues

� Vascular tissues are complex → i.e. composed of four types of cells 1. XylemXylemXylemXylem

� for transport of water & dissolved minerals absorbed by the roots from the soil � composed of fibers, parenchyma cells, vessels (large), & tracheids (small, devoid of protoplast) � Vessels & TracheidsVessels & TracheidsVessels & TracheidsVessels & Tracheids

� main water-conducting elements � exhibit secondary wall thickenings which can be annular, spiral, scalariform,

reticulate, or pitted

Xylem showing vessel elements & tracheids



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in longitudinal (left) and transverse (right) sections.

2. PhloemPhloemPhloemPhloem � for transport of food materials from the leaves to all plant parts � in woody stems, phloem tissues constitute the greater bulk of the bark � consists of fibers, parenchyma cells, & sieve tube cells (devoid of protoplast) � Sieve Tube CellsSieve Tube CellsSieve Tube CellsSieve Tube Cells

� main food-conducting elements � thick-walled & provided at both ends with perforated sieve plates

� companion cells companion cells companion cells companion cells → associated with sieve tube cells

Phloem showing sieve tube members & companion cells

in longitudinal (left) & transverse (right) sections.



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PLANT ORGANSPLANT ORGANSPLANT ORGANSPLANT ORGANS

Vegetative Plant Organs: 1. Roots 2. Stems 3. Leaves Reproductive Plant Organs: 1. Flowers 2. Fruits 3. Seeds

A. ROOTSA. ROOTSA. ROOTSA. ROOTS

Root SystemRoot SystemRoot SystemRoot System



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Monocot RootMonocot RootMonocot RootMonocot Root

Young Eudicot RootYoung Eudicot RootYoung Eudicot RootYoung Eudicot Root

1. Epidermis – uncutinized cells with root hairs (to facilitate absorption) 2. Cortex – multi-layered parenchyma cells:

� Endodermis = inner most layer (endodermal cells) � Casparian strip = suberized � Passage cells = for water transport

3. Stele – innermost cylinder � Pericycle – made up of parenchyma cells; gives rise to the vascular cambium &

secondary/lateral roots � Xylem – 3-4 radial rows of thick walled cells alternating with thin phloem cells � Vascular cambium – meristimatic zone between phloem & xylem � Phloem – thin-walled; food conducting cells alternating with xylem rays � Pith – if present, composed of parenchyma cells



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B. StemsB. StemsB. StemsB. Stems MorphologyMorphologyMorphologyMorphology

Monocot stem (cross section)Monocot stem (cross section)Monocot stem (cross section)Monocot stem (cross section)



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C. LeafC. LeafC. LeafC. Leaf

MorphologyMorphologyMorphologyMorphology

Monocot Eudicot

VenationVenationVenationVenation

Monocot Eudicot (Parallel) (Netted/Reticulated)

Simple Simple Simple Simple LeafLeafLeafLeaf

Pinnately Compound LeafPinnately Compound LeafPinnately Compound LeafPinnately Compound Leaf

Palmately Compound LeafPalmately Compound LeafPalmately Compound LeafPalmately Compound Leaf



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Leaf ArrangementLeaf ArrangementLeaf ArrangementLeaf Arrangement

AlternateAlternateAlternateAlternate

OppositeOppositeOppositeOpposite

WhorledWhorledWhorledWhorled

Monocot:Monocot:Monocot:Monocot:

Eudicot:Eudicot:Eudicot:Eudicot:



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D. FlowerD. FlowerD. FlowerD. Flower MorphologyMorphologyMorphologyMorphology

� Complete Flower – has all 4 parts (sepals, petals, pistil, stamen) � Incomplete – lacks one or more of the 4 parts � Perfect Flower (bisexual) – has both stamens & carpels/ovary � Imperfect Flower (unisexual)– has stamen or carpel but not both

Imperfect flower = Incomplete Flower � Monoecious – male & female reproductive parts in separate flowers (e.g.: corn) � Dioecious – male & female reproductive parts in separate plants (e.g.: papaya)

InflorescenceInflorescenceInflorescenceInflorescence



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E. FruitE. FruitE. FruitE. Fruit

� matured / ripened ovary

� holds & protects seeds

� Simple Fruit – developed from a single ovary

� Aggregate – several ovaries of a flower (sugar apple)

� Multiple – several ovaries of several flowers (pineapple)

TERMS:

� Pericarp - the fruit wall (derived from the ovary of the pistil) which is composed of the exocarp,

mesocarp and endocarp (the three layers are not always recognizable, ex. dry fruit)

� Endocarp - the innermost layer of the pericarp (often hard, stony or papery)

� Mesocarp - the middle layer of the pericarp (often fleshy)

� Exocarp - the outermost layer of the pericarp (often like a skin or peel). (peach)



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Types of FruitsTypes of FruitsTypes of FruitsTypes of Fruits

FleshyFleshyFleshyFleshy



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Dry FruitsDry FruitsDry FruitsDry Fruits

Dry DehiscentDry DehiscentDry DehiscentDry Dehiscent

Dry Dry Dry Dry IndehiscentIndehiscentIndehiscentIndehiscent



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F. SeedF. SeedF. SeedF. Seed Albuminous (Endospermic) Seed :Albuminous (Endospermic) Seed :Albuminous (Endospermic) Seed :Albuminous (Endospermic) Seed :

Exalbuminous (NonExalbuminous (NonExalbuminous (NonExalbuminous (Non----endospermic) Seedendospermic) Seedendospermic) Seedendospermic) Seed

plant tissues & organs

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