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BI 103: Plant-Animal

A&P

Lec 3

• Moncots vs Dicots

• Roots

Learning Objectives

What is the function of the plant root?

How are specific cells and tissues adapted

in the root in order to help it function?

How are tissues in the root different from

the leaves & stem?

How does the root filter water?

What are examples of specialized roots?

Describe mutualisms plant roots may have

with fungi & bacteria.

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Angiosperms, the

flowering plants fall

under two groups:

Monocots or Dicots

Plant Anatomy: Vegetative Organs

Leaves:

Roots:

Stem:

Form = Function

Photosynthesis

Gas exchange

Light absorption

Anchorage

Storage

Transport

Absorption

Support

Transport

Storage

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External Anatomy

of a Root

Root Cap -protects the apical meristem as the root pushes through the soil.

Root Hairs - increase the surface area of the root.

root hair epidermis

cortex

endodermis

of cortex

pericycle

xylem

phloem

apical

meristem

vascular

cylinder

root

cap

Internal Anatomy

Fig. 43-13

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Functions of Roots

Roots 1) Anchor the plant

2) Absorb & filter water

3) Absorb minerals

4) Store surplus sugars

5) Transport water, minerals and sugars and hormones

6) Produce some hormones

7) Interact with soil fungi and bacteria

DICOT MONOCOT

Organs: ROOT

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Organ: Root

1. Epidermal

Epidermis

Endodermis

Root hairs

2. Meristematic

Pericycle

3. Ground

Parenchyma

4. Vascular

Xylem

Phloem

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Organ: Root

1. Epidermal

Epidermis

Endodermis

Root hairs

2. Meristematic

Pericycle

3. Ground

Parenchyma

4. Vascular

Xylem

Phloem

1. Epidermal tissue in roots

A. Epidermis

Lacks waxy cuticle

B. Root hairs

Increase surface area for absorption

C. Endodermis

Contains casparian strip made of

suberin

Filters water

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Dermal tissue in roots

Mineral and Water Uptake by Roots vascular cylinder

xylem

pericycle endodermis

endodermal

cells

Casparian strip

cell walls

soil particles

water

root

hair

air

plasmodesmata

cortex epidermis

1

2

3

4

5

(a) Pathways of mineral and water uptake

(b) Endodermal cells, showing the Casparian strip

Fig. 43-17

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Organ: Root

1. Dermal

Epidermis

Endodermis

Root hairs

2. Meristematic

Pericycle

3. Ground

Parenchyma

4. Vascular

Xylem

Phloem

2. Meristematic

Lateral root formation

– Continues to divide, even

after mature

– Forms lateral (branch)

roots and part of the

vascular cambium

A. Pericycle

- Outer boundary of vascular cylinder

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Organ: Root

1. Epidermal

Epidermis

Endodermis

Root hairs

2. Meristematic

Pericycle

3. Ground: “Cortex”

Parenchyma

4. Vascular

Xylem

Phloem

3. Ground tissue

A. Cortex--Region of

ground tissue

B. Made up of

parenchyma cells

between epidermis

and vascular cylinder

Functions: Mostly stores

food

In the form of starch

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Organ: Root

1. Epidermal

Epidermis

Endodermis

Root hairs

2. Meristematic

Pericycle

3. Ground: “Cortex”

Parenchyma

4. Vascular

Xylem

Phloem

Root Types

Tap

Fibrous

Adventitious

- prop

- butressed

- aerial

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Taproots and Fibrous Roots Fig. 43-12

Prop Roots

Example:

Corn - Prop roots support

plants in high wind

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Buttress Roots

Stability in shallow soil

--Tropical Trees

Aerial Roots

Orchids -

Velamen roots,

with epidermis

several layers

thick to reduce

water loss

Ivies (English

ivy, Virginia

creeper) - Aerial

roots aid plants

in climbing

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Specialized roots

Contractile Roots

Pull plant deeper into the soil

Example: Trillium ovatum (Family: Liliaceae)

Specialized roots: Haustoria

Cusucuta spp.

Aka ‘Dodder’

Parasitic roots

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Specialized Roots

Pneumatophores

In plants with roots

growing in water

Spongy roots that

extend above the

water’s surface

Enhance gas

exchange between

atmosphere and

subsurface roots

Mangrove pneumatophores

Mycorrhizae: A Root–Fungus

Symbiosis

Fig. 43-19

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1. Endomycorrhizal fungi

Internal fungal associations

Also known as: vasicular-arbuscular

1. Endomycorrhizal fungi

Internal

fungal

associations

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2. Ectomycorrhizal fungi

External fungal associations

2. Ectomycorrhizal fungi

External fungal

associations

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Root Nodules House

Nitrogen-Fixing Bacteria nitrogen-fixing bacteria within

cortex cells of nodules

epidermis

nodule

Fig. 43-20