Roots

Question 1

What are 6 functions of roots?

Answer 1

1. Absorb water and nutrients
2. Conduct water and minerals to the shoots
3. Anchor and support the shoots
4. Storage
5. Sense and respond to environmental stimuli
6. Coordinate symbiotic relationships with microorganisms in the rhizosphere

Question 2

What are the 5 types of roots?

Answer 2

Radicle
Primary root
Lateral roots
Feeder roots
Adventitious roots

Question 3

What is a radicle?

Answer 3

Embryonic root

Question 4

What is a primary root?

Answer 4

Mature radicle

Question 5

What is a lateral root?

Answer 5

Roots that grow out from the primary root

Question 6

What is a feeder root?

Answer 6

The first 10 cm of a root that is in contact with the nutrient rich areas of the soil

Question 7

What is an adventitious root?

Answer 7

Roots that grow from non-root tissues

Question 8

What are the 2 types of root systems? What plants are they commonly found in?

Answer 8

Fibrous: more common in monocots
Taproot: common in eudicots

Question 9

What is the structure of the vascular tissue in roots?

Answer 9

Found in the middle. The xylem and phloem is contained in the stele in the centre of the root, surrounded by the pericycle

Question 10

What is the stele?

Answer 10

The vascular cylinder that runs through the centre of the root

Question 11

What is the pericycle?

Answer 11

Tissue surrounding the stele that can develop into lateral roots

Question 12

How do lateral roots develop?

Answer 12

The pericycle develops into the root primordia, which pushes through the cortex and breaks through the epidermis

Question 13

What two root structures are made of ground tissue?

Answer 13

Cortex and endodermis

Question 14

What is the cortex?

Answer 14

All the tissue that surrounds the vascular cylinder

Question 15

What is endodermis?

Answer 15

Inner most layer of the cortex, regulates entry into vascular cylinder

Question 16

What feature is found on the endodermis cells?

Answer 16

The casparian strips in the cell walls

Question 17

What do the casparian strips do?

Answer 17

Waxy layer that is completely impermeable to water. Forces water from the apoplastic route to the symplastic route so everything coming in has to cross a cell membrane at least once

Question 18

What are the 3 regions of a root?

Answer 18

The root apical meristem, the zone of elongation, the zone of maturation

Question 19

What happens in the root apical meristem?

Answer 19

Cell division, but no cell growth or differentiation

Question 20

What do cells of the lower layer of the root apical meristem become?

Answer 20

The root cap. Older cells get pushed off and newer cells replace them

Question 21

What do cells of the middle layer of the root apical meristem become?

Answer 21

Precursors of dermal and ground tissue

Question 22

What do cells of the upper layer of the root apical meristem become?

Answer 22

Vascular tissue

Question 23

What is the root cap?

Answer 23

Cells that cover the growing root tip

Question 24

What does the root cap do?

Answer 24

Protects the apical meristem, produces mucigel, and responds to environmental stimuli

Question 25

What is mucigel? What does it do?

Answer 25

A gel made of polysaccharides and water. It lubricates the root tip to make it easier to get through the soil and creates a favourable environment for particular microbes

Question 26

Which part of the root tip is responsible for sensing environmental stimuli?

Answer 26

Columella

Question 27

What sort of stimuli does the columella sense?

Answer 27

Gravity, moisture gradients, chemical gradients, vibrations and sounds

Question 28

What part of the root tip communicates information about environmental stimuli to the rest of the plant?

Answer 28

The transition zone

Question 29

How does the transition zone communicate information?

Answer 29

Electrical signals that are equivalent to action potentials

Question 30

What happened in the experiment with the pea plant with its roots in the two pots?

Answer 30

When there were enough nutrients in the pot with constant nutrients to complete the life cycle, the plant put most of its roots in there. If there wasn't enough, it put most of its roots in the pot with variable nutrients instead

Question 31

What happens in the zone of elongation?

Answer 31

Cells elongate and some of the ground meristem divides. Parts of the cortex start to mature and the sieve tube members mature

Question 32

What happens in the zone of maturation?

Answer 32

Cells mature and differentiate and stop elongating. Root hairs develop

Question 33

Why does no movement occur in the zone of maturation?

Answer 33

Would destroy the root hairs

Question 34

What are 7 specialized roots?

Answer 34

Adventitious, prop, epiphytic, pneumatophores, contractile roots, storage roots, haustoria (parasitic roots)

Question 35

How do monocots form the fibrous root system?

Answer 35

Adventitious roots that grow from the bottom part of the embryonic stem

Question 36

What are nodal roots?

Answer 36

Involved in vegetative reproduction. Little shootlets grow adventitious roots

Question 37

If not part of their normal life cycle, why would plants grow adventitious roots?

Answer 37

Stress response to drought or flood or wound response

Question 38

What are prop roots for?

Answer 38

Mechanical support and aiding really long branches in water absorption

Question 39

What is an epiphyte?

Answer 39

A plant that grows on another plant

Question 40

What are the challenges for epiphytes?

Answer 40

Hard to get nutrients, water, and mechanical support when you aren't in the soil

Question 41

What modification do epiphytic roots have? How does it help them?

Answer 41

A velamen, which is a thicker modified epidermis. It adheres to substrates and sucks up any water like a sponge

Question 42

What plants use pneumatophores?

Answer 42

Plants growing in water saturated, anaerobic soils. Like mangroves

Question 43

How do pneumatophores work?

Answer 43

They grow up like a snorkel and collect air for the roots under ground

Question 44

Where are contractile roots found? What do they do?

Answer 44

Found in a lot of bulbs. They contract and pull the bulb down when it gets too high up in the soil and starts photosynthesizing

Question 45

What do storage roots store?

Answer 45

Starch. Stores it in grains called amyloplasts

Question 46

What are the 2 types of mycorrhizae?

Answer 46

Ectomycorrhizae and arbuscular mycorrhizae

Question 47

How do ectomycorrhizae associate with plants?

Answer 47

Their hyphae go through cell walls and intracellular spaces and forms a sheath around the root

Question 48

How do arbuscular mycorrhizae associate with plants?

Answer 48

Form arbuscules inside the cell and exchange nutrients, water and photosynthates

Question 49

Why is forming associations with fungi and bacteria good for the plant?

Answer 49

Plants have higher rates of photosynthesis than they actually need, so they often secrete photosynthates into the soil and support entire ecosystems while getting nutrients for their troubles

Question 50

What is the "wood-wide web"?

Answer 50

A network of arbuscular mycorrhizae that connects plant roots

Question 51

What can be exchanged between plants through mycorrhizal networks?

Answer 51

Nutrients and defence compounds

Question 52

Is rhizobia a functional or taxonomic classification?

Answer 52

Functional, the bacteria aren't related

Question 53

What plant family do rhizobia associate with?

Answer 53

Fabaceae

Question 54

How do Fabaceae plants form associations with rhizobia?

Answer 54

Nitrogen stressed plants send out a chemical signal that is perceived by bacteria, which produce Nod factors in response. The Nod factors are sensed by the root hairs, and causes the plant to switch off its defence systems and envelop the bacteria in shepherd's crook structure. The bacteria get brought into the plant and it builds them a nice little anaerobic house in the epidermis and cortex