Development
Lecture Outline
Cells and Tissues of the Primary Plant Body
Primary Plant Body
Internal Organization
Tissue Systems
Ground tissue system
Vascular tissue system
Dermal tissue system
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The Big Picture
Development
Cells and tissues
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Cells and Tissues of Primary Plant Body
I. Primary plant body (herbaceous)
Primary tissue – tissue differentiated from primary meristems and
ultimately from apical meristems, herbaceous
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II. Internal Organization of Primary Plant Body
A. Cells – fundamental units of life.
B. Tissue – groups of specialized cells with common functions.
Simple tissue – tissues comprised of one cell type
Complex tissue – tissues comprised of two or more cell types
C. Tissue systems – groups of tissue that show continuity throughout plant
body.
1. dermal tissue system
epidermis (complex) tissue
2. vascular tissue system
xylem (complex) tissue
phloem (complex) tissue
3. ground tissue system
parenchyma (simple) tissue
collenchyma (simple) tissue
sclerenchyma (simple) tissue
D. Organs – Structures composed of different tissues, i.e., root, stem, leaf,
flower parts
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Distribution of tissue systems dependent on plant organ or taxon
4. General patterns:
a. Epidermis outermost in all parts
d. Leaves
-vascular tissue separate strands
(network), xylem above phloem
-ground tissue photosynthetic,
mesophyll
-phyll = leaf
b. Stem
-vascular tissue embedded in
ground tissue, forms network of
interconnected strands
-xylem internal to phloem
c. Root
-vascular tissue a solid cylinder
-xylem internal to phloem
-ground tissue only cortex
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Tissue systems/tissues
III. Ground tissue system
A. Parenchyma (simple)
B. Collenchyma (simple)
C. Sclerenchyma (simple)
IV. Vascular tissue system
A. Xylem (complex)
B. Phloem (complex)
V. Dermal tissue system
A. Epidermis (complex)
-chyma = infusion
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III. Ground Tissues
A. Parenchyma tissue (simple tissue)
1. generalized tissue in the plant body
-cortex and pith of roots and stem
-mesophyll of leaves
-flesh of fruits
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2. parenchyma cells in continuous masses
-living at maturity
-thin primary walls
-maintain ability to divide (cells with primary cell walls)
3. Used for:
-wound healing
-adventitious structures (structure arising from an unusual place,
such as roots from stems or leaves)
-photosynthesis
-storage
-secretion
-some involvement in water and solute transport (vascular tissue)
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-transfer cells involved in movement of solutes over short distances
-highly invaginated cell wall (and plasma membrane)
-in xylem and phloem of small veins of leaf
-reproductive structures: placenta, embryo sac, endosperm
-glandular structures: nectaries, salt glands, carnivorous plants
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-transfer cells -movement of substances between different symplasts (one
tissue type to another tissue)
symplats1
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B. Collenchyma tissue (simple tissue)
- in strands or cylinders beneath epidermis
- stems and petioles (leaf stalks)
- bordering veins of leaves
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4. collenchyma cells
-living at maturity
-elongated
-unevenly thickened, non-lignified primary walls
-soft and flexible
-flexible (plastic) support for elongating organs
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C. Sclerenchyma tissue (simple tissue)
1. sclerenchyma cells
-in continuous masses or small groups
-lack protoplast at maturity (dead)
-thick, lignified secondary wall
-strengthening and support (elastic)
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-fibers
long, slender
in bundles
0.8 to 70 mm
Fiber bundle
-sclereids
varied in shape
often branched
short
single or aggregated
seed coats, nut shells, endocarp of stone fruits
stone cells of pears
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IV. Vascular Tissues
A. Xylem (complex tissue)
1. principal water conducting tissue
2. nutrient conduction (via water)
3. support
4. food storage
5. several cell types involved
B. Phloem (complex tissue)
1. principal food conducting tissue
2. also composed of several cell types
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5a. tracheary elements – type of sclerenchyma (lignified)
- 2 types: vessel elements and tracheids
- elongated cells with 2nd walls
- lack protoplast at maturity (dead)
- pits in wall
- lateral movement of water
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-early formed (proto) xylem has elements with various thickenings in walls
annular – rings; weak structurally, good conductance (d,e)
helical – spirals (f)
scalariform – ladder like (g)
reticulate – network (h)
circular bordered pits (i); strong structurally, poor conductance
-later formed (meta) xylem elements tend to have reticulate to circular bordered
pits since cells do not elongate much (all such elements are tracheids)
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5b. tracheids
-only pits
-only type of water transport cell in ferns and gymnosperms
-considered less specialized than vessel elements
-sloping end walls
-occur in groups to allow water transport through pit pairs
tracheids
vessels
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5c. vessel element
-pits and perforation plates
simple perforation plate – single large opening
scalariform perforation plate – ladder-like bars
-principal water conducting cell in angiosperms
-derived from tracheids
-sloping to nearly horizontal endwalls
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-occur end to end to form vessels (several centimeters
to meters long)
-more efficient for water conduction
tracheids
vessels
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water)
6. fibers – for support
7. parenchyma – storage (mostly
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IV. Vascular Tissues
A. Xylem (complex tissue)
1. principal water conducting tissue
2. nutrient conduction (via water)
3. support
4. food storage
5. several cell types involved
B. Phloem (complex tissue)
1. principal food conducting tissue
2. also composed of several cell types
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3a. sieve elements
-2 types: sieve cells and sieve-tube elements
-have clusters of pores – sieve areas
-cytoplasma pass through sieve areas
-living cells
-newly formed cell, lose nucleus, vacuole, ribosomes, golgi, cytoskeleton
-remaining portion of cytoplasm along inside wall with ER, plastids,
mitochondria
sieve cells
sieve-tube
elements
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3b. sieve cells
-long narrow cells with sloping end walls
-pores narrow, sieve areas concentrated on
overlapping ends of cells but found over most of
cell
-less specialized cell
-food conducting in gymnosperms, ferns
-associated with albuminous cells –
specialized parenchyma cell, supports sieve cell
function
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3c. sieve tube elements
-long, broader cells with nearly horizontal end walls
-sieve areas on end walls have larger pores, make sieve plate
-sieve areas on other walls with narrow pores
-occur end to end to form sieve tubes
-considered specialized
-food conducting in angiosperms
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-associated with companion cells – specialized parenchyma cell
derived from same mother cell as sieve tube element
share many cytoplasmic connections
aids in function of sieve tube element
4. fibers – strength
5. parenchyma – storage
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V. Dermal Tissue - Epidermis (complex tissue)
1. outermost layer of cells of primary plant body
2. mostly consists of unspecialized cells without chloroplasts
3. support the cuticle
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3. other types
a. guard cells – control opening of pore (guard cell + pore = stoma or
stomate)
contain chloroplasts
associated with subsidiary cells
(reservoir of water for guard cells)
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b. trichomes – cells with appendages
root hairs – absorption of water
leaves/stems – reduce air movement or light
secretion = glands
herbivore defense (mechanical and chemical)
glands
root hairs
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4. all cells covered by cuticle on surface
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