8: Roots FINAL

1. Anchorage

2. Absorb water and nutrients

3. Conduct water, nutrients and food

4. Produce some hormones

5. Some roots are also important storage organs.

function of roots

young portions absorb, old portions anchor

do all parts of the root absorb

swollen, enlarged roots for storage

what kind of roots do cassava and kamote have

rhizoid for attachment, no conducting tissues

do mosses have roots?

1. primary roots

2. secondary roots

3. adventitious

types of roots

adventitious roots

develop from stems, leaves, and other vegetative non-root organs

prop roots

develop from the stem

primary roots

originate from the radicle

tap root

main root + 2ndary roots

fibrous root

short-lived radicle, cant see 1 major root

radicle

primordial root

taproot system and fibrous root system

patterns of root growth

Taproot system

root growth system in eudicots, gymnosperms

taproot system

digs deep into soil; old roots sa taas for anchoring sa baba for absorption

fibrous root system

• Seedless vascular plants, monocots

• Adventitious roots

• More shallow and horizontal very seldom

• Common in dry regions

because very seldom lang rain

why do fibrous roots need to be shallow and horizontal very seldom

only from region of maturation

do roots have branches/lateral appendages

endogenously from the pericycle

how do roots arise

bidirectional; produces cells towards AND away from the axis

how does root apex produce cells

calyptrogen

root cap meristem

subterminal

location of root apical meristem

root cap

Protection and aids in penetration into the soil

Peripheral cells (and epidermal cells)

secretes mucigel

Mucigel

slimy compound

• Protection

• Lubrication

• Water absorption

• Nutrient absorption

columella

contain amyloplasts. Sedimentation of these involved in the perception of gravity by roots; positive gravitropism

Quiescent center

- 500-1000 seemingly inactive cells

- arrested at G1 interphase

- divide once in 15-20days

- reservoir to replace damage meristems

- organizes the patterns of primary growth in roots

Meristem Region (region of cell division)

Region of Elongation

Region of Differentiation (maturation)

three regions of the (sub)Apical region

Meristem Region (region of cell division)

• 0.5-1.5mm behind root tip

• Area where new cells are created by mitosis

• Divide every 12-36 hours

Region of Elongation

• 4-10mm behind root tip

• Area where cells grow in length (150x)

• Long, vacuolated cells

Region of Differentiation (maturation)

• 1-5 cm behind root tip

• Root hairs

• Area where cells become specialized for different jobs, i.e. storage, protection, transport, etc.

root hairs

increase surface area for absorption

- epidermis

- cortex

- stele

which layers of the root are mature

epidermis

- protoderm

- usu. 1 cell thick

- cuticle absent

- stomata absent

- outer layer of cells, for protection and absorption

cortex

- Ground meristem

- Largest portion

- Exodermis/Hypodermis

- Parenchyma cells

- Endodermis

Exodermis/Hypodermis and Endodermis

which cells can the casparian strips be found

symplastic movement

movement of water & solutes thru tissues by passing thru interconnected protoplasts & their plasmodesmata

apoplastic movement

movement in the free space (cell walls & intercellular

spaces)

casparian strips

• Impregnated with suberin and sometimes lignin hydrophobic

• Precludes the passage of water and solutes via the tangential wall

ribbon that boxes an endodermal cell; in transverse and radial wall

itsura + location ng casparian strip

endodermis

- Casparian strip diverts water & dissolved minerals into the cytoplasm of endodermal cells

- Symplastic movement

- Prevents leaks/ back flow

- Controls flow of water into the vascular cylinder

stele

• Pericycle layer

• Vascular tissues

• Pit

pericycle

• Meristematic

• Produces branch roots (secondary or lateral roots)

• Lateral appendages form endogenously

protostelic roots

- no pith

- dicots

- Procambium forms lobed, solid core of primary xylem in the center

triarch

protostelic root w 3 lobes

tetrarch

protostelic root w 4 lobes

pentarch

protostelic root w 5 lobes

siphonostele

• roots of monocots

• A ring of vascular tissue surrounds a pith

• Polyarch - many lobes

Exarch arrangement of protoxylem

• Protoxylem differentiates from the outside

• Centripetal direction of maturation (toward inside)

endarch

arrangement of protoxylem in stems

alternate in roots, collateral in stem

Xylem & phloem in roots vs stem

secondary growth in roots

• Usually in eudicots and gymnosperms

• Absent in monocots

1. Cambium first appears on the inner side of the phloem (orange line)

2. Cambial cells produced secondary elements

3. Pericycle cells opposite the xylem lobes (yellow lines) divide to form inner cambial cells

4. Cambial cells unite to form an undulating cambium in cross section

5. Development of secondary xylem on the inner side of phloem precedes

that of secondary xylem opposite the xylem lobes

6. Vascular become circular in cross section

steps of 2ndary growth in roots

Ferns and Monocots

Siphonosteles occur in most

root

underground organ in plants that absorbs water and minerals

1. Anchorage

2. Absorption

3. Conduction

4. Hormone Production

5. Storage Organs

Five Functions of Roots

young roots

which root has the most absorption, mainly through root hairs

Auxin

a plant hormone that promotes root formation and bud growth

moss

do not have conducting tissues and do not have a root

Rhizoids

A thin, rootlike structure that anchors a moss and absorbs water and nutrients.

primary root

the first root that emerges from a seed

lateral roots

A root that arises from the outermost layer of the pericycle of an established root.

lateral roots

branch roots

adventitous roots

Specialized roots that grow from uncommon places, such as stems or leaves.

stability, support, climbing, and clinging

Function of adventitious functions

taproot system

A root system common to eudicots, consisting of one large, vertical root that produces many smaller lateral, or branch, roots.

fibrous root system

A root system common to monocots consisting of a mat of thin roots spreading out below the soil surface.

Fibrous root system

includes adventitous roots, more shallow and horizontal for survival in dry regions

root apex

tip of the root

Calyptrogen

The meristematic cells from which produces the root cap

bidirectional

Roots are ___________ because they produce cells towards and away from the axis

True

Apical meristem is subterminal (True or False)

False

Root cap is a meristematic cell (True or False)

mucigel

A slimy substance secreted by plant root caps that eases passage of the growing root through the soil.

True

Roots do not have internodes and nodes

endogenous growth

growth of lateral roots by the pericycle

root cap

a structure that covers the tip of a root, protecting the root from injury and for penetration into the soil

Polysaccharides with vitamins, enzymes, and amino acids

Composition of mucigel

1. Protection

2. Lubrication

3. Water Absorption

4. Nutrient Absorption

Functions of Mucigel

columella cells

cells of root cap associated with sensing gravity

columella cells

contain amyloplasts for storage

500-1000 seemingly inactive cells

Quiescent center contains how many inactive cells

G1 phase of interphase

cell growth, organelle duplication, protein synthesis

15-20 days

quiescent center cells divide once in ?

quiescent center

reservoir of cells to replace damaged meristematic cells

quiescent center

organizes the patterns of primary growth in roots

subapical region

3 regions: zone of cell division, zone of cell elongation, zone of cell maturation

meristem region

The region of cell division in a root is also known as __________.

0.5 - 1.1 mm behind the root cap

how far is the meristem region from the root cap

region of cell division

area where new cells are created by mitosis

12-36 hours

meristem region divides every

True

vacuoles are small in meristem region (true or false)

region of elongation

cells become several times their original length (150x)

4-10 mm

region of elongation is _________ behind the root tip

False

Region of elongation does not have long, elongated cells

region of maturation (differentiation)

region with root hairs; area where cells become specialized for different jobs: storage, protection, and transport

root hairs

tiny hair-like epidermal extensions that increase the surface area of the root allowing it to absorbs more water and nutrients

1-5 cm behind the root tip

How far is region of maturation from the root tip

No

Can you distinguish the three regions of roots?

epidermis (root)

the outermost part of the root that protects the root and for absorption

Epidermis

region of root with non-functional stomata and absent in cuticle