Plant cell walls

Question 1

What are the three layers in plant cell wall

Answer 1

Hemicellulose
Cellulose
Pectin/middle lamella

Question 2

How does a cell wall expand

Answer 2

Cell wall enzymes break connections in wall
New material is deposited
Connections remade

Question 3

Why is the cell wall of fruits and vegetables softer than other plant cell walls

Answer 3

Reduction of pectin in cell wall due to enzymes causes softening

Question 4

When is the secondary cell wall made

Answer 4

When expanding stops

Question 5

Where is the secondary cell wall located

Answer 5

Between the primary and the plasma

Question 6

What are the functions of the secondary cell wall

Answer 6

Support
Strengthen
Protect

Question 7

What macromolecules are involved in the secondary thickening of the cell wall

Answer 7

Lignin
Suberin
Cutin

Question 8

Where is there specific secondary thickening and why is it needed

Answer 8

Endodermis layer in anther
Provide strength for anther to open
When enough pressure in anther bursts open and releases pollen

Question 9

What occurs in the abscission process

Answer 9

Plant removes organs (leaves and fruit) by digesting middle lamella
Protective layer forms around abscission e.g. suberin, lignin, waterproof

Question 10

What is the major different between monocots and dicots

Answer 10

Monocots have one cotyledon

Dicots have two cotyledons

Question 11

What is the difference in leave venation between monocots and dicots

Answer 11

M - veins usually parallel

D - veins usually netlike

Question 12

What is the difference in stems between monocots and dicots

Answer 12

M - vascular bundles usually complex arrangement

D - vascular bundles usually arranged in ring

Question 13

What is the difference in roots between monocots and dicots

Answer 13

M - fibrous root system

D - Taproot usually present

Question 14

What is the difference in flowers between monocots and dicots

Answer 14

M - flowers usually in multiples of three

D - flowers usually in multiples of four or five

Question 15

What is the difference in epidermis in monocots and dicots

Answer 15

Same

Question 16

What is the difference in mesophyll layers in monocots and dicots

Answer 16

M - no difference between upper and lower

D - have palisade cells, contain many chloroplasts, bottom have spongy cells less chloroplasts

Question 17

What is the structure of a dicotyledenous root

Answer 17

Outside layer - epidermis
Multiple layers thick, mid region - cortical cells/cortex
Inside of mid region (thin band) - endodermis
Inside of endodermis - pericycle
Centre - vascular cylinder

Question 18

What is the structure of a monocotyledonous root

Answer 18

Outside layer - epidermis
Mid region - cortex
Inside of mid region (thin band) - endodermis
Same area in mid - casparian strip
Inside of endodermis - pericycle
Centre - vascular cylinder XYLEM ARRANGED IN BUNDLES IN RING SHAPE

Question 19

What is the stele made up of

Answer 19

Endodermis
Pericycle
Vascular cylinder

Question 20

What is the purpose of a casparian strip

Answer 20

Provides a protective layer - thick so is water impermeable

Roots can control what is taken into plant

Question 21

What are the two routes that nutrients can be taken up from the roots to the casparian strip

Answer 21

Apoplastic pathway

Symplastic pathway

Question 22

What is the apoplastic pathway

Answer 22

Nutrients travel between cells in the cytoplasm

Question 23

What is the symplastic pathway

Answer 23

Nutrients enter cells and leave them (travels through cells)

Question 24

Function of the root cap

Answer 24

Protect
Lubricate so can go through soil and guide root in response to gravity
Know whether going up or down

Question 25

What are meristem cells

Answer 25

Makes up root | Can be made into anything - waiting to be told

Question 26

Where does the root hair cell originate from

Answer 26

Epidermis

Question 27

Where do lateral roots form from

Answer 27

Develop in already formed primary roots | Originate from pericycle cells

Question 28

What happens when lateral roots begin to form

Answer 28

Outer tissue disformation and cell separation Signals outside cells to release cell wall modifying enzymes Allow cells around to stretch move and disengage with each other - can grow through Lateral root contains all same material as primary

Question 29

Why must the secondary wall form when lateral root has formed

Answer 29

Prevent pathogens getting in

Question 30

What do phosphorus deficient plants have to try gain more phosphorus

Answer 30

Increased lateral root and root hair production to try increase phosphorus uptake

Question 31

What is the xylem and function

Answer 31

Xylem conducts water passively | Elongated cells with secondary cell walls that lack protoplasts at maturity

Question 32

What is the phloem and function

Answer 32

Actively transport sugars and amino acids | Translocation in both directions

Question 33

How is the phloem cell wall specialised

Answer 33

Is perforated using sieve plates to allow compounds to travel through

Question 34

What does the phloem cell wall maintain even when they mature and lose their organelles

Answer 34

ER and mitochondria for energy to move all round

Question 35

What is special about a companion cell

Answer 35

Extra plasmodesmata to phloem sieve tube | Extra ribosomes and mitochondria

Question 36

What is the companion cell function

Answer 36

Support sieve tube cell

Question 37

What is the function of the sclerenchyma, and what is it

Answer 37

Provide structure and support to plant tissue | Their cell walls are thick lignified secondary walls made of cellulose and hemicellulose - often die when mature

Question 38

What is the collenchyma and its function

Answer 38

Elongated cells with thick cell walls - provide structure and support Cellulose and pectin irregularly thickened at corners

Question 39

Where are the collenchyma found

Answer 39

Under epidermis in new growth areas

Question 40

What is a trichome

Answer 40

Small hair growing from epidermis of plant, algae, lichen Can be uni/multi-cellular Can be (un)branched

Question 41

What are xerophytes

Answer 41

Adapted to prevent water loss through transpiration | Keeps air at higher humidity around stomata

Question 42

What are hydrophytes

Answer 42

Aerenchyma forms air channels - gas exchange Important for aquatic plants Stomata only on top of leaf Epidermal layer very little strengthening in stems = not rigid

Question 43

What is the function of a sclereid

Answer 43

Keeps plant together, gives structure and strength without preventing it moving in water