Cells and Tissues of the Plant Body
Vital charts and figures:
Pages 519, 526-527
Figures 23-12, 23-16, 23-22

Some terms:
•	Meristem:  a part of the plant body in which new tissue is added
–	apical meristems (primary growth)
–	lateral meristems (secondary growth)
•	Growth: irreversible increase in size
–	In plants, growth is often indeterminate (apical growth, especially)

•	Morphogenesis-- as plants grow they assume a particular form
•	Differentiation-- process by which genetically identical cells become different types
–	differential expression of genes

Primary Meristems
•	Protoderm gives rise to covering tissue 
•	Ground meristem gives rise to filling (ground) tissue
•	Procambium gives rise to vascular tissue

•	Collections of cells that provide a certain structure or function are tissues
–	tissues may be of one or several cell types
–	e.g., ground tissue is often of a single cell type (parenchyma)
–	e.g., vascular tissues (xylem and phloem) are of several cell types
Cells have primary and secondary walls
Ground Tissues
•	Parenchyma

Parenchyma
Ground Tissues
•	Parenchyma

Collenchyma

Ground Tissues
•	Parenchyma

Fibers
Sclereids
See Table pp. 526-527 
•	Parenchyma-- living at maturity, most often with primary wall, “flexible”, storage, reproduction
•	Collenchyma--living at maturity, thickened walls in corners, support
•	Sclerenchyma--dead at maturity, lignified secondary walls, support and defense
•	Fibers-- elongate, support
•	Sclereids-- branched or globular, defense

Vascular Tissues
•	Xylem
–	 Conduction of water, dissolved minerals, support.  Dead at maturity.
–	Tracheary elements (conduction), dead at maturity:  
•	tracheids
•	vessel elements
–	Parenchyma (storage)
–	Sclerenchyma fibers (support)
Vessels vs. Tracheids

A matter of pits and perforations

Tracheids
Annular and helical thickenings of vessels

Vascular Tissues
•	Phloem
–	Conduction of sugars, amino acids, lipids, hormones.  Living at maturity.
–	Sieve elements (conduction)
•	Sieve cells
•	Sieve tubes
–	Sclerenchyma  (support)
–	Parenchyma (storage and short distance transport)

•	Sieve cells have endwalls that are not as open as sieve tube elements
•	Sieve plates at ends of sieve tube elements
•	P protein
•	Companion cells

Dermal Tissues
•	Epidermal tissue
–	Unspecialized parenchyma
–	Stomata 
–	Trichomes (hairs)
•	Root hairs
•	Other hairs
•	Periderm (secondary tissue, much of this is “bark”)
Onion epidermis
Leaf epidermis has a waxy cuticle
Guard cells around stomata regulate the passage of gasses

Trichomes: root hairs
Trichomes 

Growth necessitates more covering tissue
Periderm formation
Periderm formation
Formation of Periderm