1

Plant Structure

1. What is a plant?

2. Meristems elaborate the plant body

3. Major Plant Organs: Morphology and anatomyRootsStemsLeaves

4. Tissues found in plantsGroundVascularDermal

Plant Form

Plant Organs

Shoot

Root

Leaf Anatomy

Stem Anatomy Root Anatomy

2

Cell WallApical Meristems

1. Shoot apical meristem forms 1o meristems– Protoderm– Procambium– Ground meristem

2. Root apical meristem forms 1o meristems– Protoderm– Procambium– Ground meristem

1. Primary Meristems– Protoderm, protocambium & ground meristem– Responsible for elongation growth– Types

• Shoot primary meristem• Root primary meristem

2. Secondary Meristem = Lateral meristem– Responsible for diameter growth– Types

• Vascular cambium• Cork cambium

Primary & Secondary Meristems Fig. 35.05a(TE Art)

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Apical meristemProtoderm

ProcambiumGroundmeristem

Lateralmeristems

Vascular cambiumCork cambium

Shoot Secondary Meristems

Shoot Secondary Growth

Vascular Cambium

Cork Cambium

Annual Ring

Shoot Secondary Growth

3

Root Secondary Growth

2

2. Secondary xylem

3

3. Periderm

4

4. Cork and cork cambium

1

1. Vascular cambium & 2o phloem

1

2

3

4ProtodermDermal Tissue System

EpidermisTrichomesStomatal Complexes

Ground MeristemGround Tissue System

CortexPith

ProcambiumVascular Tissue System

XylemPhloem

Apical Meristem

Primary Meristems

Primary MeristemsProduce Tissue

Systems

Ground (Fundamental) Tissue System

• Components– Parenchyma– Collenchyma– Sclerenchyma

Parenchyma

• Characteristics– Living cells– Thin, primary cell wall– Large vacuoles and thin band of cytoplasm– Store starch, oils, tannins crystals

• Where is it found?– Cortex of stems and roots– Pith of stems– Mesophyll of leaves

• Special types of parenchyma– Chlorenchyma– Aerenchyma

Parenchyma

• Special types and functions of parenchyma– Synthetic - mesophyll– Meristematic – apical meristems– Secretory – glands and nectaries– Structural - aerenchyma– Boundary - epidermis & endodermis– Transport - transfer cells

Aerenchyma in papyrus

Parenchyma

4

Leaf & Root Parenchyma

Palisade mesophyll(parenchyma)

Spongy mesophyll (parenchyma)

Root cortex (parenchyma)

Specialized Parenchyma

Aerenchyma in papyrus

Collenchyma

• Living cytoplasm• Unevenly thickened primary cell walls• Usually just beneath the epidermis• Function: flexible support

Collenchyma

Sclerenchyma

• Characteristics of sclerenchyma– Cells dead at maturity– Thick secondary cell walls– Lignified cell walls

• Types of sclerenchyma– Sclereids or stone cells - isodiametric– Fibers – very long sclerenchyma cells

Economic value: Ropes, string canvas

SclerenchymaSclereids

5

Sclerenchyma: Fibers

1. Xylem

2. Phloem

Vascular Tissue

Xylem: Tracheids and Vessel MembersVessel - Perforation

plates

Tracheid –Imperforate cell = No perforation plate

Xylem: Tracheids,Vessel Members & Perforation Plates

Simple ScalariformReticulate

Vessel MembersTracheids

Xylem Secondary Wall Architecture

Types of Secondary Wall Thickenings in Xylem1. Annular2. Helical3. Scalariform4. Reticulate5. Pitted

Xylem: Transverse section

Xylem: Longitudinal section

1 2

3

4

5

Xylem: Bordered PitsBordered Pit

6

Vascular Tissue

Xylem Phloem Fibers

Phloem

Phloem Cell CharacteristicsPhloem Anatomy

• Sieve elements– Sieve cells– Sieve tube members

• form sieve tubes

• Companion cells• Phloem parenchyma

Pores

PhloemParenchyma

1. Ordinary epidermal cells

2. Stomatal Complexes

3. Trichomes

Dermal Tissue System Types of epidermal cells

Dermal Tissue System - Ordinary Epidermal Cells

Epidermis of Galium aparine leaf

Epidermis of Zygochloa leaf (a grass)

Morphology: Wavy, elongated, tabular ≈ flattened

Tradescantia upper epidermis

7

Epidermis of Tulipa leafOleander upper epidermis

Guard cell expressing green fluorescent protein bound to talin, a protein that binds to actin filaments.

Red/orange structures are chloroplasts.

Dermal Tissue System Epidermal Cell Characteristics

Stomatal Complexes 1

2

1

3

1

34. Aglaophyton guard cells

Mullein Leaf SEM

Trichomes Trichomes

Stomatal Apparatus Cuticle

Dermal Tissue System

END