Lecture 6 - Leaves Flashcards

1
Q

What is leaf phyllotaxy?

A

Distinct arrangement of primordial at the shoot apex.

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2
Q

What does primordia arrangement lead to?

A

Leaf arrangement

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3
Q

Phyllotaxy types:

A

Helical, whorled, opposite, distichous, decussate

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4
Q

Helical (alternate, spiral)

A

One leaf per node

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5
Q

Whorled

A

3+ leaves around a single node

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6
Q

Opposite

A

Pair of leaves per node

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7
Q

Distichous

A

Leaves in 2 vertical columns on opposite sides of stem

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8
Q

Decussate

A

Successive leaf pairs are at right angles

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9
Q

What does a leaf consist of?

A

Blade (or lamina), petiole, stipules

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10
Q

What is the blade?

A

Expanded portion

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11
Q

Describe petiole.

A

Stalk-like

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12
Q

What are stipules?

A

Scale-like structures at base of some leaves

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13
Q

What is a leaf called if it lacks a petiole?

A

Sessile

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14
Q

Simple leaves

A

Undivided blade. May have lobes but gaps do not reach the vein

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15
Q

Compound leaves

A

Divided blades. Each leaflet is separated along a vein

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16
Q

Where is the bud found on compound leaves?

A

Found at the base of a leaf, but not a leaflet.

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17
Q

What plane do compound leaves and leaflets lie?

A

Leaflets- lie in same plane
leaves- extend from stem in various planes

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18
Q

What are the types of compound leaves?

A

Palmately compound, pinnately compound

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19
Q

Describe palmately compound

A

Leaflets radiate from end of petiole
No rachis

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20
Q

Describe pinnately compound

A

Leaflets arranged along rachis

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21
Q

pinnately compound: the rachis is an extension of what?

A

The petiole

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22
Q

pinnately compound: bipinnately compound leaves

A

Each leaflet is divided into smaller leaflets

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23
Q

What are the functions of a leaf?

A

Photosynthesis, transpiration, gas exchange

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24
Q

Leaf function: photosynthesis

A

Major function - need water, light, carbon dioxide, and chlorophyll

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25
Q

Leaf function: transpiration

A

Evaporation of water through leaf surfaces.

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26
Q

Leaf function: how does transpiration help?

A

Helps create negative pressure that draws water upward through the Xylem from roots

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27
Q

Leaf function: gas exchange

A
  • Carbon dioxide in for photosynthesis
  • oxygen in or out depending on concentration gradient
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28
Q

Leaf function: gas exchange: what are the functions of oxygen?

A
  • Byproduct of photosynthesis
  • used in aerobic respiration
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29
Q

What is included in the internal anatomy of the leaf?

A

Cuticle, epidermis, stomata, guard cells, mesophyll, vascular bundles (xylem, phloem)

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30
Q

What is the cuticle?

A

Waxy material on leaf surface

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31
Q

What is the function of the cuticle?

A

Moisture conservation, barrier against water loss

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32
Q

What does the epidermis do?

A

Produces the cuticle, protects enclosed tissue

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33
Q

What is the stomata?

A

Pores in the upper and lower epidermis

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34
Q

What is stomata function?

A

Allows gas exchange

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35
Q

Where are guard cells?

A

Surrounding stomata

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36
Q

What is guard cell function?

A

Open and close for gas exchange and water conservation

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37
Q

What is the mesophyll?

A

Bulk of cells between upper and lower epidermis

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38
Q

What is mesophyll shape?

A

Relatively irregular

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39
Q

What is mesophyll function?

A

Site of most photosynthetic activity of the leaf

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40
Q

What do vascular bundles consist of?

A

Xylem and phloem

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41
Q

What is Xylem function of the leaf?

A

Transports water and minerals to the leaf

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42
Q

What is phloem function of the leaf?

A

Transports photosynthesis products from origin to utilization point or storage.

43
Q

What are vascular bundles surrounded by?

A

A bundle sheath

44
Q

What is bundle sheath function?

A

Rigidity and protection for vascular tissue

45
Q

What layers is musophyll divided into in a dicot leaf?

A

Palisade mesophyll, spongy mesophyll

46
Q

Dicot leaf: palisade mesophyll location

A

Just under the Upper epidermis

47
Q

Dicot leaf: palisade mesophyll function

A

Responsible for most photosynthesis - many chloroplasts per cell

48
Q

Dicot leaf: spongy mesophyll location

A

Lower layer

49
Q

Dicot leaf: spongy mesophyll function

A

Evaporative cooling and gas exchange

50
Q

What is the shape of guard cells?

A

Kidney bean shaped

51
Q

How many mesophyll layers are in a monocot leaf?

A

Single layer

52
Q

Monocot leaf: what supports the vascular bundles?

A

Many sclerenchyma fibers

53
Q

Monocot leaf: large alls along midvein in Upper epidermis

A

Bulliform cells

54
Q

Monocot leaf: what is bulliform cell function?

A

Helps leaf fold or roll inward to conserve Walter

55
Q

What cells are associated with guard cells?

A

Subsidiary cells

56
Q

What is the cause of leaf structure variations?

A

Habitat

57
Q

What are the basic leaf variation groups?

A

Mesophytes, hydrophytes, xerophytes, halophytes

58
Q

What are mesophytes habitats?

A

Moderate habitats

59
Q

Where is the stoma in mesophytes?

A

On abaxial (lower) and adaxial (upper) surfaces

60
Q

What type of space is in the spongy mesophyll of mesophytes?

A

Intercellular spaces

61
Q

Is a cuticle present in mesophytes?

A

Yes

62
Q

What is the most common type of leaf variation?

A

mesophytes

63
Q

What is a hydrophytes habitat?

A

Wet or aquatic habitats

64
Q

Where is the stomata in hydrophytes?

A

Upper epidermis only

65
Q

What is the role of large intercellular air spaces in hydrophytes?

A

Buoyancy

66
Q

Describe the cuticle in the upper epidermis and lower epidermis hydrophytes

A

Upper epidermis- reduced cuticle
Lower epidermis- little or no cuticle

67
Q

What is the mesophyll interspersed with in hydrophytes?

A

Sclereids

68
Q

Is the leaf blade of a hydrophyte thick or thin?

A

Thin

69
Q

What leaf variation has reduced vascular tissue, especially xylem?

A

hydrophytes

70
Q

What conditions are xerophytes adapted to?

A

Arid conditions

71
Q

Where are stomata located and found in xerophytes?

A

In pockets (called crypts) and found on one epidermal surface

72
Q

Where are trichomes found in xerophytes?

A

In crypts

73
Q

What is trichome function in xerophytes?

A

Creates a micro environment that is humid

74
Q

What has small intercellular spaces in xerophytes?

A

Spongy mesophyll

75
Q

Does the epidermis have a thick or thin cuticle in xerophytes?

A

Thick

76
Q

Describe the palisade mesophyll of xerophytes and what it contains

A

May be a double layer and contain sclereids

77
Q

Describe the leaves of xerophytes

A

Small, thick, and curled

78
Q

What are halophytes adapted to?

A

Salty soil

79
Q

The stomata and mesophyll of halophytes are similar to what?

A

Xerophytes

80
Q

The cuticle of halophytes is similar to what?

A

Mesophytes

81
Q

What kind of glands do halophyte leaves have?

A

Salt glands

82
Q

How does light effect leaves?

A

Can effect size and thickness

83
Q

How do sun leaves grow?

A

Grown under high intensity light

84
Q

Name 2 features of sun leaves

A
  • Smaller and thicker than shade leaves
  • more developed palisade mesophyll
85
Q

How do shade leaves grow?

A

Grown under low light intensities

86
Q

What is leaf abscission?

A

Process of leaf loss

87
Q

Where is the abscission zone?

A

At base of petiole- region of small undifferentiated parenchyma

88
Q

Describe the process of leaf abscission

A
  • parenchyma cells divide rapidly
  • Suberin layer secreted into nearest stem walls
  • middle lamella and cell walls are broken down in the abscission zone
  • leaf is held by only a few strands of vascular tissue
  • leaf falls
89
Q

What causes Fall leaf colour?

A

Chlorophyll is degraded and carentenoids can be seen

90
Q

What is accumulated in the vacuoles of some leaves in fall?

A

Anthocyanins

91
Q

What is the photoperiod important for?

A

Triggering the fall change in pigmentation

92
Q

What are the 5 leaf modifications?

A

Bud scales, spines, tendrils, bracts, bulbs

93
Q

What do bud scales do?

A

Protect dormant buds

94
Q

Describe spines

A

Hard, dry, non-photosynthetic

95
Q

What are tendrils?

A

Modified leaves or stems that grow indefinetly and coil around objects

96
Q

What happens when a tendril touches an object?

A

The side facing the object stops growing

97
Q

What are bracts?

A

Leaf with a single flower or inflorescence in growing their axil

98
Q

What colour are bracts?

A

Green or brightly coloured

99
Q

What are bulbs?

A

An underground, swollen bud

100
Q

Where is the food of bulbs stored?

A

In the leaves

101
Q

What activity does the development of a flower end?

A

Ends meristematic activity of the vegetative shoot apex

102
Q

Development of the flower: what is the vegetative shoot apex turned into?

A

A reproductive apex

103
Q

Development of the flower: what triggers transition?

A

Environmental factors like temperature and day length

104
Q

Development of the flower: what does initiation of flower parts begin with?

A

Sepals, then petals, then stamens, then carpels