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Biosci 102 Plant structure and function > Lecture 8: Secondary growth; TIMBER! > Flashcards

Lecture 8: Secondary growth; TIMBER! Flashcards

1
Q

What does anticlinal division promote?

A

breadth; perpendicular to the meristem

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2
Q

What does periclinal division promote?

A

depth; new cell wall parallel to the outside

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3
Q

true or false; secondary growth is rare for monocots

A

true

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4
Q

What is the purpose of the vascular cambium?

A
  • adds secondary xylem (wood) and secondary phloem, increasing vascular flow and support for the shoot system
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5
Q

What does vascular cambium develop into

A

wood

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6
Q

What does cork cambium develop into

A

bark

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7
Q

what are the two lateral meristems of secondary growth?

A

cork cambium
vascular cambium
- overall increases the girth of the stem

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8
Q

What is the purpose of the cork cambium

A

produces tough, thick covering
- consisting mainly of wax impregnated cells that protect the stem from water loss and from invasion by insects, bacteria, fungi

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9
Q

true or false; secondary growth occurs simultaneously with primary growth

A

true

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10
Q

true or false; secondary growth occurs both inwards and outwards

A

true

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11
Q

What is bark made of?

A

all the tissues outside the vascular cambium

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12
Q

What does the bark consist of in trunks?

A

bark = phloem+ cortex+ periderm

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13
Q

What does the bark around roots consist of?

A

bark = phloem + periderm

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14
Q

true or false; in woody roots, cortex dies and is sloughed off

A

true

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15
Q

What is the Cork Cambium

A
  • cork tissue functions as a barrier that helps protect the stem. root from water loss; physical damage; pathogens
  • produces protective covering on secondary plant body
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16
Q

Where does the cork cambium originate in stems?

A

-originates from layer immediately beneath epidermis

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17
Q

Where does the cork cambium for roots originate?

A

pericycle

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18
Q

Where is the cork located? And what is its’ function?

A

outside from the cork cambium

  • consists of cork cells that accumulate to the exterior of the cork cambium
  • as cork cells mature they deposit a waxy material called suberin in their walls then die
  • because they are lined with suberin and wax
  • protective layer of the plant
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19
Q

what is the phelloderm?

A
  • thin layer of parenchyma cells that forms the interior of the cork cambium
  • living parenchyma
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20
Q

true or false; cork cells are dead at maturity

A

true

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21
Q

Why are cork cells impermeable to water and gases

A

they are lined with suberin and waxes

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22
Q

What is the consequence of the stem/root splitting as it gets older?

A

it loses its meristematic activity and differentiates into cork cells
- a new cork cambium forms to the inside, resulting in another layer of Periderm; older layers of periderm are sloughed off

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23
Q

the formation of bark depends on?

A

the phelloderm, cork cambium and cork

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24
Q

What are lenticels

A

these are ‘dots on the periderm’

  • the inter cellular spaces allow gas exchange between the cells and the atmosphere
  • raised circular or oval areas
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25
Q

What are the downfalls of periderms?

A

pathogens can enter through them

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26
Q

Why is respiration via the periderm necessary?

A

allows the release of stored energy

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27
Q

Describe the vascular cambium

A
  • one cell thick (in atypical woody stem; the VC consists of a continuous cylinder of undifferentiated parenchyma cells)
  • highly vacuolated
  • dense initials
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28
Q

What is residual procambium?

A

fascicular cambium

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29
Q

What do you call parenchyma between vascular bundles

A

interfascicular cambium

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30
Q

How does the VC divide?

A

Periclinaly

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31
Q

What are the two types of meristematic cells that the VC consists of?

A

fusiform initials

ray initials

32
Q

What is the orientation of fusiform initials?

A

vertical

33
Q

Where is the secondary phloem

A

outside

34
Q

Where is the secondary xylem

A

inside

35
Q

What is the orientation of ray initials?

A

horizontal

36
Q

What are ray cells made of

A

parenchyma

37
Q

What are the shape of fusiform cells

A

longer/ wide

38
Q

ray intials

A

square/ elongated

39
Q

what is the purpose of ray initials

A

radial files that connect the secondary xylem with the secondary phloem; the cells of vascular ray move water and nutrients between the secondary xylem and phloem store carbohydrates

40
Q

Describe secondary xylem and phloem

A 
elongate longitudinally (vertical)
- conduct water and food
41
Q

What are rays for?

A 
elongate radially (horizontal)
- for food storage, ad transport across wood
42
Q

true or false; wood is mostly secondary xylem and fibres

A

true

43
Q

true or false; secondary phloem is crushed during growth

A

true

44
Q

What are the three different planes you can cut wood

A

transverse
radial
tangential

45
Q

What does transverse cut mean

A

slice across trunk

46
Q

What does radial slice mean

A

slice cut parallel with radius

47
Q

what does tangential cut mean

A

longitudinal slice, not parallel with radius

48
Q

When are growth rings produced?

A

annually

49
Q

What causes false rings

A

climate change

50
Q

When is early wood formed?

A

early spring; in temperate regions

51
Q

When is late wood formed

A

late summer

52
Q

What is the appearance of early wood

A

large xylem cells

thin cell walls

53
Q

What is the appearance of late wood

A

narrow cells; thick & dense cell walls

54
Q

What happens when there is slow growth

A

results in less early wood and therefore harder wood

55
Q

What is the purpose of early wood

A

maximizes the delivery of water to newly growing leaves

56
Q

What is the purpose of late wood

A

support

- don’t transport as much water but contributes more to stem or root support

57
Q

Why does the heartwood become non functional as the tree trunk matures?

A
  • blockages appear in the xylem (tyloses)
  • fill with resins, gums, tannins, or other dark pigmented materials
  • heartwood (dark)
  • can also be due to infection
58
Q

true or false; only thick walled phloem fibres remain

- as primary phloem is crushed and pushed outward

A

true

59
Q

What is heartwood

A

older layers of secondary xylem no longer transporting water and minerals (xylem sap)
- close to centre of the stem/ root

60
Q

Why is heartwood dark

A

due to resins, tannins, pigments, etc…

61
Q

What is sapwood

A

the newest layers of secondary xylem still transport xylem sap (usually has large circumference)

62
Q

Why does the sapwood and secondary phloem increase in circumference?

A

to supply the increasing number of each years’ leaves

63
Q

what does the periderm consist of?

A

cork cambium, phelloderm, cork

64
Q

What is timber like for angiosperm trees?

A

known as hardwood

  • high lignin content
  • vessels + tracheids
65
Q

What is is timber like for gymnosperms?

A

softwood

  • low lignin
  • tracheids only
66
Q

What are the 4 characteristics of wood

A

grain
color
density
knots

67
Q

What causes grain?

A

alignment of xylem cells
- can be parallel to the trunk or slanted or spiral
-

68
Q

What is the density of balsa

A

0.13 g/cm^3

69
Q

what is the density of pine

A

0.4 (for construction)

70
Q

What is the density of oak

A

0.6 (for furniture

71
Q

What does knots mean

A

bases of branches which have been covered by subsequent secondary growth

72
Q

How does the color of timber come about

A

impregnation of xylem by colored compounds eg. tannins, resins

73
Q

What are the properties of the Teak wood

A
  • naturally resistant to insects, warping, splintering and the elements
  • ideal wood for creating furniture
74
Q

Where is Teak planted?

A

Indonesia (bu the Dutch in 1800)

75
Q

How long does Teak reach maturity?

A

50 -60 years

76
Q

How much of the Papuan Kwila is logged illegally?

A

70 - 80 %

77
Q

What do virgin forests influence?

A

climate patterns; rain

Biosci 102 Plant structure and function (9 decks)

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