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