26-Aug-13

1

Plant Anatomy and Tissue Structures

The Two Major

Plant Systems

Reproductive shoot (flower)

Terminal bud

Node

Internode

Terminal bud

Vegetative shoot

Blade

Petiole

Stem

Leaf

Taproot

Lateral roots Root

system

Shoot

system

Axillary bud

Angiosperm plants

have threse major

organs:

Roots

Stems

Leaves

& Flowers

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2

The Three

Tissue Systems

Dermal

tissue

Ground

tissue Vascular

tissue

Common

Types of

Plant Cells

Parenchyma cells 60 m

PARENCHYMA CELLS

80 m Cortical parenchyma cells

COLLENCHYMA CELLS

Collenchyma cells

SCLERENCHYMA CELLS

Cell wall

Sclereid cells

in pear 25 m

Fiber cells

5 m

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3

Common Types of Plant Cells WATER-CONDUCTING CELLS OF THE XYLEM

Vessel Tracheids 100 m

Tracheids and vessels

Vessel

element

Vessel elements with

partially perforated

end walls

Pits

Tracheids

Common Types of Plant Cells

SUGAR-CONDUCTING CELLS OF THE PHLOEM

Companion

cell Sieve-

tube

member

Sieve-tube members:

longitudinal view

Sieve

plate

Nucleus

Cytoplasm

Companion

cell

30 m

15 m

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4

Dermal

Ground

Vascular

Key

Cortex Vascular cylinder

Epidermis

Root hair

Zone of

maturation

Zone of

elongation

Zone of cell

division

Apical

meristem

Root cap

100 m

Tissue

Organization of

Roots

DICOT root • Organized xylem structure- bundles are

arranged in a ring • example is a sunflower root • fewer root hairs than monocots

Some MONOCOT root • Unorganized xylem structure -scattered amongst cell in bundles • example is a corn root • many root hairs

Tissue Organization of Roots

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5

Tissue Organization of Stems

Xylem Phloem

Sclerenchyma

(fiber cells)

Ground tissue

connecting

pith to cortex

Pith

Epidermis

Vascular

bundle

Cortex Key

Dermal Ground Vascular

1 mm

(a) An eudicot stem (sunflower)

Ground

tissue

Epidermis

Vascular

bundles

1 mm

(b) A monocot stem (maize)

Key

to labels

Dermal

Ground

Vascular

Guard

cells

Stomatal pore

Epidermal

cell

50 µm

Surface view of a spiderwort

(Tradescantia) leaf (LM) (b)

Cuticle

Sclerenchyma

fibers

Stoma

Upper

epidermis

Palisade

mesophyll

Spongy

mesophyll

Lower

epidermis

Cuticle

Vein

Guard

cells

Xylem

Phloem

Guard

cells

Bundle-

sheath

cell

Cutaway drawing of leaf tissues (a)

Vein Air spaces Guard cells

100 µm Transverse section of a lilac

(Syringa) leaf (LM) (c)

Tissue

Organization Of

Leaves

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6

Meristematic Tissue Within the meristems certain cells are able to divide

repeatedly into two sister cells: 1. Initial - the self perpetuating sister cell that remains in the

meristem

2. Derivative - the other sister cell which moves into the plant body. These may also continue to divide until they become differentiated into specific types of cells

There are two types of meristems: Apical & Lateral

(a) Apical Meristematic Tissue

Apical Meristem occur at the tips of the roots and shoots and they are

responsible for extension of the plant body.

Apical meristems give rise to the primary tissues of the plant, forming

the primary plant body.

Since there are three tissue systems in plants, the apical meristem gives

rise to three primary meristems:

1) Protoderm - gives rise to the outer, protective coating of the plant

2) Procambium - gives rise to the vascular tissue

3) Ground meristem - gives rise to ground tissue

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(b) Lateral Meristematic Tissue Lateral Meristem responsible for lateral growth and they produce

the secondary tissues which constitute the secondary plant body

Lateral meristems are called cambia (cambium).

There are two types: 1) Vascular cambium - gives rise to secondary vascular tissue, xylem to the

inside and phloem to the outside 2) Cork cambium - gives rise to mostly cork. It lies outside the vascular

cambium.

Intercalary meristems: Some grasses have neither a vascular cambium nor a cork cambium, but have this one. They develop at intervals along stems, and their tissues added to stem length

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Vascular

cambium

Cork

cambium

Lateral

meristems

Root apical

meristems

Primary growth in stems

Epidermis

Cortex Primary phloem

Primary xylem

Pith

Secondary growth in stems

Periderm

Cork cambium

Cortex

Primary

phloem

Secondary phloem

Vascular cambium

Secondary

xylem

Primary

xylem

Pith

Shoot apical

meristems

(in buds)

Primary and Secondary Growth

Vascular cambium

Pith

Primary xylem

Secondary xylem

Vascular cambium

Secondary phloem

Primary

phloem

Periderm

(mainly cork

cambia

and cork)

Pith

Primary xylem

Vascular cambium

Primary phloem

Cortex

Epidermis

Vascular cambium

4 First cork cambium

Secondary xylem

Pith

Primary xylem

Vascular cambium

Primary phloem

2

1

6

Primary xylem

Secondary xylem

Secondary phloem

Primary phloem Cork

Phloem ray 3

Xylem ray

Bark

8 Layers of

periderm

7

Cork

5 Most recent cork cambium

Cortex Epidermis

9

Secondary phloem

Primary and

secondary

growth in a

two-year-old

stem

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9

Anatomy Of A Tree Trunk

Growth ring

Vascular ray

Heartwood

Sapwood

Vascular cambium

Secondary phloem

Layers of periderm

Secondary

xylem

Bark

Secondary phloem

Vascular cambium Late wood

Early wood Secondary

xylem

Cork

cambium

Cork

Periderm

Xylem ray

Bark

0.5 mm 0.5 mm

Transverse section of a three-year-old

stem (LM)

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10

Tissue Organization Of Flower

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11

Plumule - Embryo shoot