Botany Lecture - Chapter 5

8/12/2019 Botany Lecture - Chapter 5

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ChapterTissues and the

primary growth ofstems

Rossdvasquez 2013


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The tallest living tree is the Stratosphere Giant in

Humboldt Redwoods State Park, California. At 112.34

meters (308.62 feet) , it is five stories taller than the

Statue of Liberty.


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Plant Body is composed of primary and secondary tissues

PRIMARY PLANT BODY:- herbaceous plant body

SECONDARY PLANT BODY:

- woody plant body


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Plant Body is composed of primary and secondary tissues


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Tissuegroup of of cells that perform specific

function or functions.

Classification:

1. Based on stage of development

a. Embryonic or meristematic

b. Permanent

2. Based on composition

a. Simple

b. complex


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Meristematic tissues where the cells are in the mitotic

state

Classification:

1. Based on initiating cells

a. Primary meristem (primordial meristem)

b. Secondary meristem

2. Based on position in the plant body

a. Apical

b. Intercalary

c. lateral

3. Based on function

a. Protoderm (DERMATOGEN)

b. Procambium (PLEROME)

c. Fundamental or ground (PERIBLEM)


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Overview of primary meristems and tissues


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Permanentcells are stable, no longer dividing

- differentiated into 2 types

Types:

1. Simple permanent tissue

- composed of one type of cells

- differentiated into dermal or protective and

ground or fundamental

2. Complex permanent tissue- composed of different kinds of cells but

perform similar function.


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Epidermis(simple dermal)

Outermost surface ofa herbaceous stem,leaf, root

Uses: protection Regulate exchange of

materials

Encrusted with cutin(cuticle)

Contains guard cells,Guard cells


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Epidermis Accessory cellsserves as

reservoir of water and ions

Bulliform cellslongitudinal rows of

vacuolated cells

- Loses loss turgor pressure Epidermal hairelongation of the

epidermal cell outward

(trichome and root hairs)

Differences:

1. Location 3. structure

2. Function
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-shade leaves from excess light

-protect plants from insects

-aid in nutrient uptake

-help disperses seeds

Cotton trichomes canbe made into threads,

which are then woven

into cloth

TrichomesEpidermal Outgrowths / Hairs


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Epidermal hairs

GLANDULAR STINGING

BRISTLE SCALE STELLATE BRANCHING

1. Glandular or Secretory

2. Non-Glandular / Non-secretory


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Root hairs epidermal outgrowth of roots epidermis

- increase surface area for absorption

Root hairs of

germinated seed


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Cork or Phellem(simple dermal)

Outer covering of woody

stems and roots

Cell wall impregnated with

suberin Produced by the cork

cambium (secondary

meristem)

No intercellular spaces

L ti l l h d t di t t f


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Lenticels lens-shaped spot or pores on dicot stem for gaseous

exchange

HARVESTING OF CORK FROM PHELLODENDRON TREE


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HARVESTING OF CORK FROM PHELLODENDRON TREE

P h ll h if l thi ll ll


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Parenchyma cells have uniformly thin cell walls.

Thin walled primary wall

Alive at maturity

Isodiametric shape

large vacuole

Specialized for photosynthesis(chlorenchyma)

Specialized for gas exchange

capacity - large intercellular

spaces (aerenchyma)

Specialized for short distancetransport of solutes (transfer cells)

Storage (storage parenchyma)

Chl h ll h i l d i


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Chlorenchyma cells are parenchyma involved in

photosynthesis

Cross section of a leaf blade (dicot)


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Storage parenchyma cells

of potato

Other types of parenchyma cells are glandular cells,

transfer cells, storage cells.

Mucilage from

Venus Flytrap

Mucilage from Okra

C ll h ll h i ll th t thi k d


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Elongated cells with

unevenly thickened non

lignified primary wall Plasticity

Found in elongating tips and

vines

Aerial roots of epiphytes

Collenchyma cells have primary walls that thickened

in the corners.

C ll h ll ll f d b l th


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Collenchyma cells are usually found below the

epidermis or bands next to the vascular tissues

S l h h b th i d thi k


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Walls are elastic

Arise from parenchyma due totension

Dead at maturity (in some) Support and strengthening tissues

Two types of cells:

1. conducting

2. mechanical

2.1. sclereids

2.2. fibers

Sclerenchyma has both a primary and thick

secondary wall that is lignified.

S l id h t d i di t i ith t


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Sclereids are short and isodiametric, with strong

walls, brittle and inflexible, protective in function

Fib l fl ibl l h d f t


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Fibers are long, flexible sclerenchyma, wood of most

flowering plants

Flax fiberscommon source for paper and

linen cloth


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The Vascular Tissue System

Two complex tissues:

1. xylembrings water and mineral saltsfrom the roots to the rest of the

plants.

2. phloem- moves sugar and other

organic nutrients


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Complex permanent tissues

1. Xylem

- transport water and minerals from the roots to stemand to the leaves

- thick lignified wall , dead at maturity

- primary xylem - procambium- protoxylemshort lived, replaced by new

protoxylem (outer)

- metaxylem formed after elongation of stem/root(inner)

- secondary xylem (wood) vascular cambium- inner layer of the bark

- conducting cells (xylary elements) :

tracheids and vessel elements


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1.Tracheids

1. long cells with tapered

ends.

2. Only type of waterconducting cells in

ferns, conifers and

most other non

flowering plants.

3. Dead at maturity

4. Secondary wall has

pits

The conducting cells of Xylem


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Pits are the gaps in the

secondary walls.

Bordered pits make theopening narrower, acting

like a valve.


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Secondary Wall thickenings in Tracheids and

vessel elements


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Vessel elements

1. Dead at maturity

2. Cell walls formhollow tubes,

3. Wider, shorter, and

less tapered

4. With perforation

plate

5. Joined together to

form a pipe or

tube


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Phloemfood conducting tissues

1. Sieve tube members

- alive and active

- Presence of sieve

plates

- No nucleus- Forms continuous

connection of

cytoplasm from the

top to bottom

- 2. Companion cells

nucleated, supply

proteins to sieve

tubes


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Complex permanent tissues

1. Phloem- transport dissolved organic

compounds (sucrose)

- thin walled primary wall

- primary phloem - procambium

- protophloemelongating regions(outer); short - lived

- metaphloemnon elongatingregions (inner)

- secondary phloem vascular cambium

- inner layer of the bark

- sieve elements: sieve cells, sieve tubemembers (companion cell)


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Phloem

Companion cells small cells attached

to the sieve cells

-Possess a nucleus

-Regulate the loading and unloading ofcarbohydrates from the sieve

tubes

Sieve tubes vertical rows of

elongated cells

-Possess a protoplasm but

no nucleus

-Walls are perforated with pits

-Perforated end walls serve asstrainer (sieve plate)


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Secretory Cells

Not classified but incorporated

with other tissues Two types External (nectary, hydathodes,

digestive glands, salt glands)

Internal (resin ducts, laticifers)


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Nectary (Floral)

- secrete nectar or sugary

exudates

1. for attractionfloral

2. for protection

extrafloral


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hydathode

parenchyma

Hydathodes (water glands)

secrete water via guttation,

relieve p r e s s u r e b u i l d - u p


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Digestive glands

secrete enzymes

that digest

trapped insects


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Salt glands

Salt glands dump sites for excess salt absorbed from a

salty (saline) environment- leaf of mangroves.


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Secretory cells

(internal)

Internally located cells that exude

protoplasmic products influenced by

pressure or lysis of cell wall

Secretory cells large cells contain

substances ( oil, mucilage)


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Secretory cells

Basil oil and fragrances

Internal


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Internalresin ducts used as storage of

secreted oils and resins.

RESINS- AMBER

-flammable with

turpentine and rosins.

-aromatic


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LATICIFERSsecretory cells with primary

wall secreting latex; seal wounds

and protection


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Internallaticifers

Articulated laticifers Non articulated

laticifers


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End for Tissues!

Thank you FOR LISTENING!

Ross D. Vasquez Ph.D.

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Botany Lecture - Chapter 5