Plants: Lecture 5

Question 1

Types of Meristems?

Answer 1

There are two types of meristems:

Apical Meristems
Lateral Meristems

Question 2

Apical meristems?

Answer 2

Responsible for primary growth in roots and shoots. They are in all vascular plants.

Question 3

Lateral meristems?

Answer 3

Composed of the vascular cambium and cork cambium, in change of secondary growth in all woody plants - not monocots. Only in woody eudicots and conifers. They make wood and bark.

Question 4

What is there product of secondary growth and what does it occur in?

Answer 4

Secondary growth produces wood and bark, and occurs in conifers and woody eudicots.

Question 5

Where is the vascular cambium?

Answer 5

It is located between the xylem and phloem of the primary tissues in the vascular bundle.

Question 6

What is made by the vascular cambium?

Answer 6

The vascular cambium makes secondary xylem and secondary phloem.

Question 7

What is the secondary xylem?

Answer 7

It is the tissue made inward from the vascular cambium. It is also what we traditionally call wood and is made by the vascular cambium

Question 8

What is the secondary phloem?

Answer 8

Secondary phloem is made outward from the vascular cambium, and controls the flow of sugar water.

Question 9

Primary phloem and xylem after vascular cambium development?

Answer 9

The primary xylem and phloem are fully non-functional after the development of the secondary xylem and phloem. They are also completely split apart at this point.

Question 10

What does the cork cambium make?

Answer 10

The cork cambium is what makes the protoderm (bark/cork of the tree). Both the secondary phloem and everything outward from it make up the bark of a tree.

Question 11

Palm trees not being a real tree?

Answer 11

They have lignin but don’t go through the process of making a vascular and cork cambium so they are not actually woody.

Question 12

Creation of secondary xylem and phloem?

Answer 12

1. Secondary xylem is to the inside and makes wood
2. Secondary phloem is to the outside and part of bark.
3. More Vascular cambium added to increase in circumference.
4. Rays of parenchyma are present for lateral transport

Question 13

How do trees thicken?

Answer 13

Most of the thickening is from the secondary xylem, and each year it thickens much more than the phloem does, causing the creation of rings.

Question 14

What else does the vascular cambium make?

Answer 14

The vascular cambium is also charged with making rays.

Question 15

What do fusiform initials make?

Answer 15

Fusiform initials make tracheids and vessel elements (xylem) alongside sieve elements (phloem).

• They are tapered cells that make these items.

Question 16

What do ray initials make?

Answer 16

Ray initials make rays in both xylem and phloem. Rays are tissues that help move fluids laterally across the plant.

Question 17

Heartwood vs. Sapwood?

Answer 17

Heartwood is darker and older wood, whereas sapwood is younger and lighter wood.

• It is thought that heartwood might have materials that aren’t very good for the cell within them.

Question 18

What is wood and what polymer is in it?

Answer 18

Wood is secondary xylem.

• The polymer lignin is in the secondary walls of tracheids and vessel elements.
• In other words, wood is woody because the walls of tracheids and vessel elements are impregnanted with large quantities of lignin.

Question 19

Why are there growth rings?

Answer 19

Growth starts and stops based on what season it is. This rhythm creates the rings we see, which represent 1 year each.

Question 20

What is lignin?

Answer 20

Lignin is deposited in cell walls, filling spaces and binding cellulose, hemicellulose, and pectin.

• It gives strength to bark and wood
• It can be seen in the cell walls of non-woody plants as well (bamboo, palms, wheat straw)

Question 21

What trend do we see when looking at tree rings under a microscope?

Answer 21

We see that there are bigger cells at the beginning of the year, which is why we are able to differentiate years. They get smaller as the meristems split more and more.

Question 22

What is the cork cambium?

Answer 22

It is a new type of lateral meristem.

• It arises from the cylinder of cortex cells outside the vascular cambium and secondary phloem.
• It produces the 3 layers of the periderm.

Question 23

What are the three layers of the periderm?

Answer 23

• Phelloderm to the inside (a thin layer of parenchymal cells)
• The cork cambium itself
• Cork to the outside (Suberized, dead cells that protect the woody plant from pathogens and losing water).

Question 24

Components of bark?

Answer 24

All tissues outside of the vascular cambium.

• Living phloem
• Cork Cambium
• Cork

*latter two also make up the periderm

Question 25

What is the technical (biological) meaning of sap?

Answer 25

Sap is composed of the water and minerals that go upward from the soil through the xylem.

Question 26

1st Law of thermodynamics?

Answer 26

We cannot create nor destroy energy, it can only change from one form to another - electricity to light

Question 27

What is the 2nd law of thermodynamics?

Answer 27

Energy spontaneously tends to flow from being concentrated in one place to becoming spread out - In other words: for a combined system and surroundings, entropy will never decrease.

Question 28

The second law in life?

Answer 28

The movement of fluid in plants follows the second law of thermodynamics. - The most equitable distribution of energy corresponds to maximum entropy

Question 29

Examples of the second law in life?

Answer 29

- Osmosis - Diffusion - Fluid movement because of differences in hydrostatic (water) pressure

Question 30

Baking soda + water example?

Answer 30

Water goes to the baking soda spontaneously. This is what happens in plants. Adding solute causes water to want to go there because of a difference in potential energy

Question 31

Transport overview?

Answer 31

Water and minerals are taken up the roots - the ascent of sap. CO2 goes in and O2 goes out. When light comes in, sugar is transported downward toward the roots. Root respiration also has CO2 out and O2 in as a gas exchange.

Question 32

What are the different routes of water movement?

Answer 32

Apoplastic: travels within the cell membranes Symplastic: travels within the cytosol Trans-membrane: travels both within and alongside the membrane at different times.

Question 33

What is cytoplasm vs. cytosol?

Answer 33

Cytoplasm: all material inside the cell membrane Cytosol: the part of the cytoplasm excluding the organelles.

Question 34

Cell walls hydrophilic?

Answer 34

Cell walls are generally hydrophilic and soak a lot of water up.

Question 35

What is cellulose?

Answer 35

- main component of cell walls - highly water absorbent - polysaccharide - most abundant organic compound on earth

Question 36

Uses of cellulose?

Answer 36

- Rayon - Cotton - Paper - Cellulose sponges

Question 37

Water potential energy (Psi)?

Answer 37

Water potential energy is measured in megapascals (MPa) - 1 MPa = ~10 atmospheres (bars)

Question 38

What does water potential consist of?

Answer 38

It combines the effects of solute concentration and pressure.

Question 39

What direction does water flow in?

Answer 39

Water flows from regions of higher to lower water potential.

Question 40

When is Psi = 0?

Answer 40

it equals 0 MPa for pure water at sea level and at room temperature. - It determines the direction of the movement of water.

Question 41

Adding solutes - Water potential?

Answer 41

Adding solutes lowers water potential where the solutes are.

Question 42

Positive pressure - water potential?

Answer 42

Positive pressure means that pressure is being put on one side - therefore it will move to the opposite side.

Question 43

negative pressure - water potential?

Answer 43

This is also known as tension and pulls toward, creating lower water potential in the direction of the pulling

Question 44

Cell in sugar water?

Answer 44

If the potential is less than the cellar rest than the water in the cell will go into the sugar water, causing the membrane to shrivel inwards.

Question 45

Adding to pure water?

Answer 45

Adding to pure water will mean that the potential inside the ell is greater, therefore more water will be pulled into the cell.

Question 46

What is plasmolysis?

Answer 46

Plasmolysis is the loss of water from the cell by osmosis. This results in the cell membrane becoming separated from the cell wall.

Question 47

Lateral transport of water and minerals?

Answer 47

Water enters the root hairs and travels toward the xylem in the middle of the cell. It cannot pass the casparian strip and instead goes around and has to cross the cell membrane - this gives it the opportunity to turn away unwanted/unneeded components that the cell does not benefit from.

Question 48

Apoplast?

Answer 48

nonliving continuum outside the cytosol, including: - Cell walls - Xylem cells - Extracellular spaces

Question 49

Symplast?

Answer 49

Continuum of cytosol is connected by the plasmodesmata.

Question 50

The endodermis?

Answer 50

A cylinder that is one cell thick

Question 51

Stele?

Answer 51

All the material inside the endodermis. - Xylem and phloem - Pith - Pericycle (origin of lateral roots)

Question 52

Casparian Strip?

Answer 52

- Where primary walls and middle lamella were - Waterproof and impermeable to ions: suberin - All water and ions entering the xylem must pass through the endodermal cells, and must cross the cell membrane

Question 53

What is Mycorrhizae (mycorrhizal fungi)?

Answer 53

A mutualism between plants and fungi. - They increase root surface area - Aid the absorption of materials into the roots. - known as a mycorrhizal association.

Question 54

Pathway of water and minerals?

Answer 54

1. Soil 2. Root hair or micorrhizae 3. Cortex 4. Endodermis 5. Xylem 6. Atmosphere - Every step has a lower water potential and therefore moves spontaneously without any energy expended.

Question 55

Theoretical possibilities of water and mineral movement?

Answer 55

1. Capillary Action 2. Pumps From above: atmospheric pressure. From below: root pressure 3. Transpiration - Cohesion - Tension mechanism

Question 56

Steps of the transpiration-cohesion- tension mechanism?

Answer 56

- Water evaporates from moist cells in leaf stomates (low atmospheric pressure) through transpiration - Water potential is lowered at air-water interface, causing negative pressure (tension) in the xylem - Hydrogen bonds hold water molecules together (cohesion) - Xylem under tension gradient: pressure potential is lowest at the top - Thus, water is pulled up by pressure gradient (difference in pressure potential not solute) - Water and minerals enter root by osmosis.

Question 57

Generation of transpirational pull?

Answer 57

Negative pressure (tension) at the air-water interface in the leaf is the basis of transpirational pull, which draws water out of xylem.

Question 58

TTC mechanism: Facts?

Answer 58

- total path in xylem from highest to lowest water potential - Passive process - Tracheids and vessel elements are dead cells - Moves upward only.

Question 59

2 main components of TTC?

Answer 59

1) water spontaneously moves from higher to lower pressure 2) air has lower pressure and creates a strong pull creating the most pressure (most negative) at the top.

Question 60

Stomates open?

Answer 60

Cues to open include: - Light - CO2 depletion - Circadian rhythm

Question 61

Dry conditions effect on stomata?

Answer 61

Abscisic acid: hormone - Causes potassium to leave guard cells - Stimulates stomate closure

Question 62

Xylem movement?

Answer 62

Passive, only moves in one direction.

Question 63

Phloem movement?

Answer 63

Requires energy and active.