Lecture 6 - Leaves Flashcards
(104 cards)
1
Q
What is leaf phyllotaxy?
A
Distinct arrangement of primordial at the shoot apex.
2
Q
What does primordia arrangement lead to?
A
Leaf arrangement
3
Q
Phyllotaxy types:
A
Helical, whorled, opposite, distichous, decussate
4
Q
Helical (alternate, spiral)
A
One leaf per node
5
Q
Whorled
A
3+ leaves around a single node
6
Q
Opposite
A
Pair of leaves per node
7
Q
Distichous
A
Leaves in 2 vertical columns on opposite sides of stem
8
Q
Decussate
A
Successive leaf pairs are at right angles
9
Q
What does a leaf consist of?
A
Blade (or lamina), petiole, stipules
10
Q
What is the blade?
A
Expanded portion
11
Q
Describe petiole.
A
Stalk-like
12
Q
What are stipules?
A
Scale-like structures at base of some leaves
13
Q
What is a leaf called if it lacks a petiole?
A
Sessile
14
Q
Simple leaves
A
Undivided blade. May have lobes but gaps do not reach the vein
15
Q
Compound leaves
A
Divided blades. Each leaflet is separated along a vein
16
Q
Where is the bud found on compound leaves?
A
Found at the base of a leaf, but not a leaflet.
17
Q
What plane do compound leaves and leaflets lie?
A
Leaflets- lie in same plane
leaves- extend from stem in various planes
18
Q
What are the types of compound leaves?
A
Palmately compound, pinnately compound
19
Q
Describe palmately compound
A
Leaflets radiate from end of petiole
No rachis
20
Q
Describe pinnately compound
A
Leaflets arranged along rachis
21
Q
pinnately compound: the rachis is an extension of what?
A
The petiole
22
Q
pinnately compound: bipinnately compound leaves
A
Each leaflet is divided into smaller leaflets
23
Q
What are the functions of a leaf?
A
Photosynthesis, transpiration, gas exchange
24
Q
Leaf function: photosynthesis
A
Major function - need water, light, carbon dioxide, and chlorophyll
25
Leaf function: transpiration
Evaporation of water through leaf surfaces.
26
Leaf function: how does transpiration help?
Helps create negative pressure that draws water upward through the Xylem from roots
27
Leaf function: gas exchange
- Carbon dioxide in for photosynthesis
- oxygen in or out depending on concentration gradient
28
Leaf function: gas exchange: what are the functions of oxygen?
- Byproduct of photosynthesis
- used in aerobic respiration
29
What is included in the internal anatomy of the leaf?
Cuticle, epidermis, stomata, guard cells, mesophyll, vascular bundles (xylem, phloem)
30
What is the cuticle?
Waxy material on leaf surface
31
What is the function of the cuticle?
Moisture conservation, barrier against water loss
32
What does the epidermis do?
Produces the cuticle, protects enclosed tissue
33
What is the stomata?
Pores in the upper and lower epidermis
34
What is stomata function?
Allows gas exchange
35
Where are guard cells?
Surrounding stomata
36
What is guard cell function?
Open and close for gas exchange and water conservation
37
What is the mesophyll?
Bulk of cells between upper and lower epidermis
38
What is mesophyll shape?
Relatively irregular
39
What is mesophyll function?
Site of most photosynthetic activity of the leaf
40
What do vascular bundles consist of?
Xylem and phloem
41
What is Xylem function of the leaf?
Transports water and minerals to the leaf
42
What is phloem function of the leaf?
Transports photosynthesis products from origin to utilization point or storage.
43
What are vascular bundles surrounded by?
A bundle sheath
44
What is bundle sheath function?
Rigidity and protection for vascular tissue
45
What layers is musophyll divided into in a dicot leaf?
Palisade mesophyll, spongy mesophyll
46
Dicot leaf: palisade mesophyll location
Just under the Upper epidermis
47
Dicot leaf: palisade mesophyll function
Responsible for most photosynthesis - many chloroplasts per cell
48
Dicot leaf: spongy mesophyll location
Lower layer
49
Dicot leaf: spongy mesophyll function
Evaporative cooling and gas exchange
50
What is the shape of guard cells?
Kidney bean shaped
51
How many mesophyll layers are in a monocot leaf?
Single layer
52
Monocot leaf: what supports the vascular bundles?
Many sclerenchyma fibers
53
Monocot leaf: large alls along midvein in Upper epidermis
Bulliform cells
54
Monocot leaf: what is bulliform cell function?
Helps leaf fold or roll inward to conserve Walter
55
What cells are associated with guard cells?
Subsidiary cells
56
What is the cause of leaf structure variations?
Habitat
57
What are the basic leaf variation groups?
Mesophytes, hydrophytes, xerophytes, halophytes
58
What are mesophytes habitats?
Moderate habitats
59
Where is the stoma in mesophytes?
On abaxial (lower) and adaxial (upper) surfaces
60
What type of space is in the spongy mesophyll of mesophytes?
Intercellular spaces
61
Is a cuticle present in mesophytes?
Yes
62
What is the most common type of leaf variation?
mesophytes
63
What is a hydrophytes habitat?
Wet or aquatic habitats
64
Where is the stomata in hydrophytes?
Upper epidermis only
65
What is the role of large intercellular air spaces in hydrophytes?
Buoyancy
66
Describe the cuticle in the upper epidermis and lower epidermis hydrophytes
Upper epidermis- reduced cuticle
Lower epidermis- little or no cuticle
67
What is the mesophyll interspersed with in hydrophytes?
Sclereids
68
Is the leaf blade of a hydrophyte thick or thin?
Thin
69
What leaf variation has reduced vascular tissue, especially xylem?
hydrophytes
70
What conditions are xerophytes adapted to?
Arid conditions
71
Where are stomata located and found in xerophytes?
In pockets (called crypts) and found on one epidermal surface
72
Where are trichomes found in xerophytes?
In crypts
73
What is trichome function in xerophytes?
Creates a micro environment that is humid
74
What has small intercellular spaces in xerophytes?
Spongy mesophyll
75
Does the epidermis have a thick or thin cuticle in xerophytes?
Thick
76
Describe the palisade mesophyll of xerophytes and what it contains
May be a double layer and contain sclereids
77
Describe the leaves of xerophytes
Small, thick, and curled
78
What are halophytes adapted to?
Salty soil
79
The stomata and mesophyll of halophytes are similar to what?
Xerophytes
80
The cuticle of halophytes is similar to what?
Mesophytes
81
What kind of glands do halophyte leaves have?
Salt glands
82
How does light effect leaves?
Can effect size and thickness
83
How do sun leaves grow?
Grown under high intensity light
84
Name 2 features of sun leaves
- Smaller and thicker than shade leaves
- more developed palisade mesophyll
85
How do shade leaves grow?
Grown under low light intensities
86
What is leaf abscission?
Process of leaf loss
87
Where is the abscission zone?
At base of petiole- region of small undifferentiated parenchyma
88
Describe the process of leaf abscission
- 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
What causes Fall leaf colour?
Chlorophyll is degraded and carentenoids can be seen
90
What is accumulated in the vacuoles of some leaves in fall?
Anthocyanins
91
What is the photoperiod important for?
Triggering the fall change in pigmentation
92
What are the 5 leaf modifications?
Bud scales, spines, tendrils, bracts, bulbs
93
What do bud scales do?
Protect dormant buds
94
Describe spines
Hard, dry, non-photosynthetic
95
What are tendrils?
Modified leaves or stems that grow indefinetly and coil around objects
96
What happens when a tendril touches an object?
The side facing the object stops growing
97
What are bracts?
Leaf with a single flower or inflorescence in growing their axil
98
What colour are bracts?
Green or brightly coloured
99
What are bulbs?
An underground, swollen bud
100
Where is the food of bulbs stored?
In the leaves
101
What activity does the development of a flower end?
Ends meristematic activity of the vegetative shoot apex
102
Development of the flower: what is the vegetative shoot apex turned into?
A reproductive apex
103
Development of the flower: what triggers transition?
Environmental factors like temperature and day length
104
Development of the flower: what does initiation of flower parts begin with?
Sepals, then petals, then stamens, then carpels
