Secondary growth and water relations of the cell

Question 1

Why don’t plants fall over as they increase in height?

Answer 1

Compensate for increased height by adding bulk and strength to their stems.

Question 2

What is lateral/secondary growth concerned with?

Answer 2

Increasing plant girth and strength

Question 3

What is the purpose of primary growth?

Answer 3

Establishing the architecture of the plant.

Question 4

where is primary growth from?

Answer 4

Root apex and shoot apex,

Question 5

Which meristems are associated with primary growth?

Answer 5

SAM and RAM

Question 6

What meristem is associated with secondary growth?

Answer 6

The cambium

Question 7

What is the pattern of tissue as you move further down from the SAM?

Answer 7

Tissue gets older as you move further down from the SAM.

Question 8

When does metaxylem form?

Answer 8

After the tissue/organ it is associated with has completed growth/elongation.

Question 9

How does water move in and out of the metaxylem.

Answer 9

The metaxylem has perforations that allow for water movement.

Question 10

What type of tissue is wood?

Answer 10

Secondary xylem

Question 11

Explain why wood is so light even though it is so strong.

Answer 11

Wood is mostly air. Tough tubes with mainly air inside.

Question 12

What is the main difference between the xylem of gymnosperms and the xylem of angiosperms?

Answer 12

Xylem of gymnosperms only has tracheids. The xylem of angiosperms contains both tracheids and vessels.

Question 13

How does secondary growth occur?

Answer 13

By the addition of new xylem and phloem to the primary stem to make a secondarily-thickened stem

Question 14

Provide examples of plants that undergo secondary growth.

Answer 14

Trees, shrubs (woody dicots)
conifers (gymnosperms)

Question 15

How do meristems add to girth?

Answer 15

mainly lateral divisions

Question 16

Is this picture an image of primary or secondary growth? Identify the names of the labels.

Answer 16

Primary growth
A = phloem
B = (pro)cambium
C = xylem

Question 17

Where does primary growth occur?

Answer 17

In the vascular bundles

Question 18

How does secondary growth start?

Answer 18

A new meristem is introduced between the vascular bundles.

Question 19

What is interfascicular cambium?

Answer 19

Meristem that arises between vascular bundles

Question 20

What is fascicular cambium?

Answer 20

The meristem inside the vascular bundles

Question 21

What is the cambial ring?

Answer 21

Eventually the cambial cells unite to form a ring of meristematic tissue within the stem. These cells eventually differentiate to form rings of secondary xylem and phloem

Question 22

What are initials?

Answer 22

Meristematic cells that can give rise to other cell types.

Question 23

What does the addition of new cells do to the meristem?

Answer 23

Addition of new cells pushes the circumference of the meristem out.

Question 24

Give a general of radial growth in the meristem.

Answer 24

Cell of vascular cambium divides -> one cell differentiates into xylem, one stay meristematic -> division -> one cell differentiates into phloem, the other remains meristematic -> divisions and differentiation continue

Question 25

How do cambial cells add xylem or phloem?

Answer 25

Cambial cells divide in longitudinal periclinal fashion. Gives rise to either 1 phloem cell + 1 initial or 1 xylem cell + 1 initial

Question 26

How do initials add to the vascular cambium? Why do they do this?

Answer 26

To add to vascular cambium, initials divide anticlinally. They do this to compensate for increasing girth.

Question 27

Where is the cambium located?

Answer 27

Between xylem and phloem.

Question 28

Is this an image of an angiosperm or gymnosperm? How can you tell?

Answer 28

Angiosperm

Question 29

Locate the cambium, xylem and phloem in this image.

Answer 29

Question 30

How old is this tree? How do you know?

Answer 30

3 because there are three rings of xylem present.

Question 31

Does this wood belong to an angiosperm or a gymnosperm? How do you know?

Answer 31

Gymnosperm because there are no vessels present.

Question 32

What are the red arrows pointing to? What do these things do?

Answer 32

Resin ducts/canals are toxic and help protect against microbial growth and predators. They can also turn into amber.

Question 33

Outline the general transition from primary to secondary growth.

Answer 33

1. Isolated procambial strands begin to differentiate. 2. Primary xylem and phloem form 3. Cambial ring forms, secondary growth commences 4. Cork cambium and periderm develop

Question 34

How does secondary growth change based on the season?

Answer 34

Slower growth in autumn and winter than in spring and summer.

Question 35

What kind of information do annual rings provide us with?

Answer 35

Rate of growth, amount of lignification

Question 36

What are possible explanations for figured wood?

Answer 36

Mutations; bacteria that invade plant genome (plant cells grow like crazy, producing substances only bacteria can consume)

Question 37

What is the function of vascular rays?

Answer 37

Transport substances in and out of xylem rings; storage to support cambial growth after winter.

Question 38

How is the xylem of heartwood characterized?

Answer 38

Xylem is no longer functional

Question 39

How is the xylem of sapwood characterized?

Answer 39

Most likely still functional (more likely the closer you get to cambium); unlignified.

Question 40

What do fusiform cells produce?

Answer 40

Elements of secondary xylem and phloem

Question 41

What do ray initials give rise to?

Answer 41

Rays

Question 42

What are the two cell types in the vascular cambium?

Answer 42

Fusiform initials and ray initials

Question 43

What type of cells are ray cells?

Answer 43

Living parenchyma

Question 44

WHich is more abundant, secondary xylem or secondary phloem?

Answer 44

Secondary phloem.

Question 45

What is the function of lenticels?

Answer 45

Allow entrance of oxygen to outer cells inside the bark.

Question 46

Where do lenticels generally arise?

Answer 46

Where stomata were present on the primary stem.

Question 47

Do monocots have secondary growth?

Answer 47

No, only eudicots.

Question 48

How is the woody characteristic achieved in monocots?

Answer 48

Extensive primary thickening, especially in leaf bases; phloem remains active for longer periods of time

Question 49

Which cells are active in secondary phloem?

Answer 49

Only the youngest. The rest are crushed.

Question 50

Where does the cork cambium arise?

Answer 50

Below epidermis.

Question 51

WHat does the cork cambium give rise to?

Answer 51

Outer bark

Question 52

List some reasons why water is important to plants.

Answer 52

- Hydrates cell contents, acts as a solvent - Participates in biochem reactions - Medium for transport of solutes - Maintains shape - Needed for cell expansion and growth - Cooling

Question 53

How much of the water that enters through the roots is transpired?

Answer 53

>99%

Question 54

What causes wilting?

Answer 54

Leaf having less than the full amount of water they can have

Question 55

Why might some leaves wilt and others not in a plant?

Answer 55

a) Doesn't have enough water and is allocating water to areas where growth is most important b) Has enough water but some factor (such as infection) is preventing movement of water to certain areas. c) Too much water in soil (kills/reduces function of root system)

Question 56

How can plants regulate temperature?

Answer 56

Evaporative transpiration used for cooling (like sweating)

Question 57

How do cells elongate?

Answer 57

Water entering cell and then into vacuole, weakening cell wall, expanding cell wall.

Question 58

Why can plant cells grow so quickly?

Answer 58

Elongation essentially just happens due to water. Don't require as much new cytoplasm to be produced, thus requiring less energy.

Question 59

What regulates the loosening of the cell wall, etc. during elongation?

Answer 59

Cytoskeleton, specifically microtubules and actin. Direct enzymes used.

Question 60

How do you calculate the water content of a tissue/organ/plant?

Answer 60

Fresh weight - dry weight = (water + cell wall weight + cell content weight) - (cell wall weight + cell contents)

Question 61

What is osmosis?

Answer 61

Movement of water across cell membrane according to relative concentrations of dissolved substances inside and outside cell.

Question 62

How do cells enable osmosis?

Answer 62

Selective membrane permeability

Question 63

WHy is the cell wall necessary in plants in relation to water?

Answer 63

Able to resist pressure, prevents cell from bursting.

Question 64

What are the two selectively permeable membranes located in plant cells?

Answer 64

Plasma membrane and tonoplast

Question 65

What do aquaporins do?

Answer 65

Aid in faster movement of water across membranes

Question 66

What is water potential? What is the variable used to denote it?

Answer 66

The chemical potential of water, referred to as psi.

Question 67

What is the psi of distilled water in an open glass container at sea level?

Answer 67

0

Question 68

In which direction does water move?

Answer 68

From high water potential to low water potential

Question 69

What happens to psi when solutes are added to water?

Answer 69

It is lowered because energy is used to dissolve said solutes

Question 70

What is the osmotic potential of water? What represents it?

Answer 70

Difference between potential of pure water and water plus solute. Represented by psi pi.

Question 71

How does increasing pressure affect psi?

Answer 71

Increases because energy is gained with added pressure.

Question 72

What is the pressure potential? What is it denoted by?

Answer 72

Difference between potential of pure water and water under pressure. Represented by psi p.

Question 73

Is positive or negative pressure used during transpiration?

Answer 73

Negative; water being 'sucked up'

Question 74

What is the water potential equation?

Answer 74

osmotic potential + pressure potential (+ possibly psi m)

Question 75

When is dynamic equilibrium reached in the cell?

Answer 75

when psi pi = psi p, water potential of cell = 0. Occurs in fully hydrated cell

Question 76

What is the wilting point?

Answer 76

When water potential is equal to osmotic potential, pressure potential = 0

Question 77

What unit is psi expressed in?

Answer 77

MPa

Question 78

What is the matrix potential?

Answer 78

Potential to absorb water, psi m

Question 79

Is the matrix potential positive or negative? Why?

Answer 79

Negative, water loses energy when absorbed.

Question 80

When is matrix potential significant?

Answer 80

In dry plants/parts and drought situations