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Tissues and the Primary Growth of Stems (Internal Organization of Stems:…
Tissues and the Primary Growth of Stems
Basic Types of Cells and Tissues
Parenchyma
Most common type of cell and tissue
Alive at maturity
Types of parenchyma cells
Flower petals
Fruits
Cells that produce nectar, fragrances, resins, oils
Thin primary walls
Collenchyma
Unevenly thickened primary walls
Alive at maturity
Provide plastic support
Can be stretched
Produced in shoot tips and young petioles
Sclerenchyma
Primary cells plus secondary walls.
Dead at maturity
Elastic support and Tracheary elements
Involved in water trasnport
Supports cell by strength alone
Stretch to absorb water
Two types of Sclerenchyma
Mechanical "Nonconducting"
Sclereids
Isodiametric
Dead at maturity
Fibers
Long
Many types dead
Alive involved in storage
Conducting "Tracheary Elements"
Tracheids
Long and narrow with tapered ends
No perforations
Dead at maturity
Found in all vascular plants
Vessel Elements
Short and wide
Perpendicular end walls
One or two perforations
Dead at maturity
Exclusively in flowering plants
Nonflowering plants
Vessels
Ferns
Horsetails
Gymnosperms
External Organization of Stems
Shoot
Stem+leaves, flowers, or buds
Bulbs
Corms
Rhizomes
Tubers
Stem
An axis
Node
Internodes
Wide
Narrow
Intermediate
Phyllotaxy
Alternate
One per node
Opposite
Two per node
Decussate
Four rows
Whorled
Three or more per node
Spiral
Leaves not aligned with nearest neighbors
Distichous
Two rows only
Leaf axil
Axillary bud
Bud scales
Internal Organization of Stems: Arrangement of Primary Tissues
Epidermis
Single layer of thin parenchyma cells
Cutin "Cuticle"
Wax
Stoma "Stomata"
Guard cells
Stomatal pore
Trichomes "Hairs"
Cortex
Photosynthetic parenchyma and collenchyma cells
Fleshy stems
Parenchyma is aerenchyma
Vascular Tissues
Xylem
Conducts water and minerals
Dead hollow cells
Phloem
Distributes sugars and minerals
Living cells
Not a circulatory tissue
Xylem
Tracheids
Shape:
Long/Narrow
Ends pointed
Secondary Wall
Annular
Helical
Scalariform
Reticulate
Circular bordered pits
Perforations
None
Vessel Elements
Shape:
Short/Wide
Ends flat
Secondary Wall
Annular
Helical
Scalarform
Reticulate
Circular border pits
Perforations
Two
One in each end wall
Terminal members with only one
Phoelm
Sieve Cells
Shape:
Long/narrow
Ends pointed
Sieve areas:
Small
Located over all cell surface
Associated cells
Albuminous cells
Plant division:
All non angiosperm vascular plants
Sieve Tube Members
Shape:
Short/wide
Ends flat
Sieve areas:
On side walls
On end walls
Sieve plate
Large end wall
Associated cells:
Companion cells
Plant Division:
Angiosperm only
Vascular Bundles
Eudicots
Pith
Monocots
Scattered
Collateral
Xylem Strand
Primary Xylem
Phloem Strand
Primary Phloem
Stem growth and Differentiation
Apical Meristems
Subapical Meristem
Protoxylem
Cells dead at maturity
Metaxylem
Protopholoem
Cells short lived
Function for one day
Metaphloem
Large sieve areas
Conspicuous companion cells
