Lecture 4- Plant Structure; Cell Types and Primary Growth

Question 1

There are two systems in vascular plants

Answer 1

Shoot system: above ground, consists of shoot with nodes, depends on water and minerals
Root system: below ground, depends on photosynthates

Question 2

Root

Answer 2

an organ that anchors a vascular plant in the soil
absorbs minerals and water
stores carbohydrates

Question 3

Primary root

Answer 3

The first root (and organ) to emerge from a germinating seed
Originates in the embryo
Branches to form lateral roots

Question 4

Lateral root

Answer 4

Greatly enhances the ability of the root system to anchor the plant and acquire water and minerals from soil

Question 5

Taproot

Answer 5

One main vertical root
Develops from the primary root
Prevents the plant from toppling
Allows plant to be tall

Question 6

Stem

Answer 6

An organ that raises and separates leaves, exposing them to sunlight
Raise reproductive structures, facilitates the dispersal of pollen and fruit
Consists of nodes: points at which leaves are attached
internodes: the stem segments between nodes

Question 7

Axillary bud

Answer 7

Structure that can form a lateral shoot, called a branch

Young ones grow very slowly

Question 8

Apical bud

Answer 8

Also called terminal bud
Composed of developing leaves, nodes, and internodes
The shoot tip, where most of the growth of a young shoot is

Question 9

Leaf

Answer 9

The main photosynthetic organ

Consist of a blade and a petiole

Question 10

Blade

Answer 10

Hard, flat part of leaf

Question 11

Petiole

Answer 11

The stalk that joins the leaf to the stem at a node, the soft part

Question 12

Cell Walls

Answer 12

Extracellular- outside the membrane and is made by the membrane
Composed mostly of cellulose: polysaccharide of glucose units
Made of cellulose microfibrils: adjacent, parallel cellulose molecules

Question 13

There are two kinds of cell walls in land plants:

Answer 13

primary and secondary

Question 14

primary cell wall

Answer 14

Primary wall
Thin
In all plant cells
Made first

Question 15

secondary cell wall

Answer 15

Secondary wall
Thicker than primary wall, made for strength
In some plant cells 
Made on the inside 
Made seconds
Provides support and protection

Question 16

Functions of the Plant Cell Wall

Answer 16

Determines and maintains cell shape

Provides support and mechanical strength
allows plants to get tall, hold out thin leaves to obtain light

3) Prevents the cell membrane from bursting
resists water pressure

4) Controls the rate and direction of cell growth and regulates cell volume
5) Ultimately responsible for the plant architectural design
6) Physical barrier to a) pathogens and b) water in suberized (waxy) cells. However, remember that the wall is very porous and allows the free passage of small molecules

7) Carbohydrate storage
the components of the wall can be reused in other metabolic processes (especially in seeds)

Question 17

The cell wall is composed of 3 polysaccharides:

Answer 17

cellulose, hemicellulose, pectin

Question 18

cellulose

Answer 18

Polymer (chain) of up to 25,000 glucose molecules
approx 36 chains bond to make microfibril
made up of cellulose microfibrils

Question 19

hemicellulose

Answer 19

Cross-linking glycans bond with cellulose

Question 20

pectin

Answer 20

Jellylike, acts as the glue

Holds everything together

Question 21

why do cells stick together

Answer 21

middle lamella: pectic substances

Question 22

types of plant cells

Answer 22

6:
Schlerenchyma
Parenchyma
Epidermal
Collenchyma
Trachieds and vessel elements
Sieve elements

Question 23

Schlerenchyma

Answer 23

-thick secondary wall: strong and woody 
two types: fibres that unite into strands, schlerieds that don't unite
-dead and hard
function: support, strength 
-ex: rope, clothing

Question 24

Parenchyma

Answer 24

-Simple cells that have generalized functions
Least specialized
Usually lack secondary wall
Can often divide and differentiate at maturity
most abundant, can perform all kinds of functions based on their location
Function:
General
Most metabolic processes (photosynthesis, storage, secretion)

ex: fruit flesh, pith, and cortex of stems and roots

Question 25

Epidermal

Answer 25

Epidermal
Outermost cells of all land plants
Single layer 
Function:
Waterproofing: keeps water out and in
Protection from bacteria, fungi, viruses
Can be highly specialized: make hairs (trichomes) , nectar, guard cells- gas exchange 
Cuticle
Formed by the epidermal cells
Outermost part is wax
Waxy coating on the epidermal surface, helps prevent water loss, pathogens, and UV radiation

Question 26

Collenchyma

Answer 26

Thick, uneven primary wall
No secondary wall
Often occur in strands 
Alive at maturity: can elongate 
Function:
Support, especially of young and growing organs 

ex: celery leaf and midrib and petiole

Question 27

Tracheids and vessel elements

Answer 27

Water conducting cells of the xylem
Dead at maturity (when they are functioning, they are dead)
Secondary wall lignified: woodlike polymer, often spiral
Two kinds: tracheids and vessel elements
Function:
Support
Supply of water and minerals

Xylem tissue: tracheids and vessel elements
Differ in their shape

Tracheids
In the xylem of all vascular land plants
Tapered, goes through pit

Vessel Elements
Wider, shorter, not tapered
Thick, stacked on top of each other

Question 28

Sieve elements

Answer 28

Sieve elements
Sugar conducting cells of the phloem
Alive at maturity
With companion cell: connected to the sieve-tube by plasmodesmata
Function:
Transport sugars (especially sucrose) in liquid form, other organic compounds, some minerals

Question 29

Meristem

Answer 29

Ultimate source of all parts of mature sporophyte
Undifferentiated
Can divide forever

Question 30

Two types of meristems

Answer 30

Apical and Lateral

Question 31

Apical Meristems

Answer 31

• Shoot and Root AM
• Make 3 meristems, those meristems go off to make 3 primary tissues
• primary growth: growth in height
• located at tips of roots and shoots

Question 32

Describe primary growth

Answer 32

1) Apical meristem produces 3 new meristems: Protoderm that goes on to produce dermal tissue/epidermis. Pro cambium goes on to produce vascular tissue/ xylem to inside, phloem to outside. Ground meristem produces ground tissue: pith and cortex, lies in-between protoderm and pro cambium
Allows plant to grow vertically

Question 33

Draw a shoot apical meristem

Answer 33

youngest tissues at top

oldest are at the bottom

Question 34

Shoot structure of Monocot and Eudicot

Answer 34

fff

Question 35

Root apical meristem drawing

Answer 35

k

Question 36

root cap is produced by the

Answer 36

protoderm

• protects root as it drives down into the soil
• dead cells

Question 37

Stele

Answer 37

• protects all vascular tissue in the root

- all vascular tissue

Question 38

Primary growth in roots

Answer 38

1) Zone of Cell division. Root AM keeps dividing in cells.
2) Zone of Elongation. Root cells get longer and grow
3) Zone of Maturation/Differentiation: cell growth stops, root hairs grow

Question 39

Root structure in Monocot and Eudicot

Answer 39

ss

Question 40

Endodermis

Answer 40

innermost layer of cortex
one cell thick barrier between cortex and vascular tissue
-casparian strip: permits passage

Question 41

Stele

Answer 41

all vascular tissue in root and stem
everything inside endodermis
pericycle