Plant Structure Flashcards
1
Q
Shoots
A
Consist of stems and leaves
2
Q
Types of shoots
A
Can be vegetative (leaf bearing)
Or
Reproductive (flower bearing)
3
Q
Apical meristems
A
Tips of the stem or roots
4
Q
Lateral meristems
A
Laterally located in stems and roots
5
Q
Taproot
A
Main vertical root
6
Q
Eudicot root systems
A
Have a taproot with lateral roots (or branch roots) that arise from the taproot
7
Q
Monocot root systems
A
Fibrous root system
Adventitious roots that arise from stems or leaves
Lateral roots that arise from the adventitious roots
8
Q
4 main functions of roots
A
Absorb nutrients
Absorb water
Anchorage
Storage of carbohydrates
9
Q
3 key tissues in plants
A
Roots
Stems
Leaves
10
Q
Where does leaf stalk attach to the stem
A
Petiole
11
Q
Axillary bud
A
At the same point as the petiole
12
Q
Different types of roots
A
Storage roots
Prop roots
Buttress roots
Aerial roots
Pneumatophores
13
Q
Prop roots
A
Grow out from the stem
Important in shallow soils or soils with low structural integrity
14
Q
Aerial roots
A
Strangling
Aerial roots sent to ground eventually wrap around the host tree
Eg strangler fig
15
Q
Pneumatophores
A
Air roots
Negatively gravitropic
Provide adequate aeration
Eg mangroves
High salt concentration in sap as found in saline/aquatic environments
16
Q
Buttress roots
A
Important for anchorage
17
Q
Node
A
Where the petioles leave the stem
18
Q
Internodes
A
Segment of stem between nodes
19
Q
Where does extension growth of the plant occur
A
Apical meristem
Internodes are of increasing length
20
Q
Intercalary meristems
A
Allow damaged leaves to regrow
21
Q
Basal meristems
A
In some monocots, particularly grasses
Meristem activity occurs at the base of the stem and leaves
22
Q
Function of stem
A
Transport of nutrients and water
Structural support
Photosynthesis
Specialised adaptations- eg thorns, climbing
Storage
Asexual propagation
23
Q
Phytomere
A
a unit of plant growth that consists of a node associated with a leaf and a subtending internode which has a tiller bud at its base
24
Q
Rhizomes
A
Horizontal stems that grow underground
25
Leaf structure
consist of a flattened blade and a stalk called the petiole, which joins the leaf to a node of the stem
26
Compound leaf
Made up of many leaflets
27
Tubers
Swollen ends of stolons specialised for food storage
28
Sessile leaves
Grasses and many other monocots have sessile leaves - lack petioles
29
Monocot leaf venation
Veins usually parallel
30
Eudicot leaf venation
Veins usually net-like
31
Monocot stems
Vascular tissue scattered
32
Eudicot tissue
Vascular tissue arranged in ring
33
Bulbs
Consist mostly of the swollen bases of leaves that store food
34
Evolutionary adaptations of leaves
Tendrils
Spines
Storage leaves
Reproductive leaves
Bracts
Insectivorous plants (digestive function)
35
Leaf function
Photosynthesis
Transpiration
Gas exchange
36
Tendrils
Allow plant to climb
Eg grapes or peas
37
Bracts
a modified leaf or scale, typically small, with a flower or flower cluster in its axil.
Bracts are sometimes larger and more brightly coloured than the true flower, as in poinsettia.
38
Reproductive leaves
Leaves of some succulents produce adventitious plantlets
39
40
Leaf colouration
Attracts pollinators
Eg red attracts hummingbirds
41
3 tissue systems in vascular plants
Vascular tissue
Dermal tissue
Ground tissue
42
Dermal system in non-woody plants
Consists of the epidermis
43
Dermal system in woody plants
The periderm replace the epidermis in older regions of stems and roots
44
Dermal cell types
Epidermis
Guard cells
Trichomes
Root hairs
45
Function of dermal system
Mechanical support
Protection
Restriction of transpiration and aeration of the plant body
46
Arrangement of subsidiary cells
Anomocytic
Diacytic
Anisocytic
Paracytic
47
Anomocytic
Lacks subsidiary cells
48
Diacytic
2 cells one at each pole
49
Anisocytic
3 cells of unequal size
50
Paracytic
2 cells laterally arranged
51
Cyclocytic
Ring of equally sized cells
52
Actinocytic
Radiate strongly
53
Function of trichomes
Reduce evaporation by covering stomata, openings
Protect leaves from high intensity light and UV radiation
Buffer against temperature fluctuations
Regulate plant growth and shape by sticking flower plants together to help reproduction
Facilitate climbing, growth forms
Absorption of water and minerals
54
Trichomes
Hair like outgrowths of the epidermis
Can be single or multi cellular
Occur on stems, leaves and reproductive organs
55
How are Trichomes protective
Can secrete sticky or toxic substances
56
Phytoliths
Silica bodies found in plant tissues
Make grass more abrasive and difficult to digest
57
58
Vascular system
Consists of the xylem and phloem
59
Xylem function
Conducts water upward and dissolved substances throughout all the organs of the plant
60
Xylem structure
Elongated cells with tapered ends
Possess thick walls
Tracheids
61
Tracheids
In gymnosperms and seedless vascular plants (ferns etc)
Tapered at each end
Overlap with each other
At overlap there are pits enabling flow of water between tracheids
62
Vessels
Angiosperms contain some narrow tracheids but also have long tubes made up of individual wider cells
Open at both ends sometimes with a grid at the end (perforation/scalariform plates)
63
Phloem
Sieve elements with sieve plates at the ends of each cell
64
Sieve cells
Gymnosperms
Lack sieve plates
Have an albuminous cell derived from the parenchyma
65
Sieve tube elements
Angiosperms
Sieve plates
Adjacent companion cells
66
Pits
Small areas in tracheids where no secondary wall material has been deposited
Allows flow of water between adjacent cells
67
Lignin
Form thick secondary walls
Strengthens the cellulose cell walls before the protoplast dies
68
Why do sieve tube elements need companion cells
They lack a nucleus
69
Plasmodesmata
Cytoplasmic connections between adjacent companion cells and sieve tube members
70
71
2 types of ground tissue
Pith
Cortex
72
Ground tissue internal to vascular tissue
Pith
73
Ground tissue external to vascular tissue
Cortex
74
What kinds of specialised cells are found in ground tissue
Storage
Photosynthesis
Support
75
3 tissue types in ground tissue
Parenchyma
Collenchyma
Sclerenchyma
76
Parenchyma cells
Most abundant type fills most of the cortex and pith
Have thin and flexible primary walls
Least specialised
Perform the most metabolic functions
Retain the ability to divide and differentiate- living at maturity
77
Function of parenchyma
Storage of starch
Photosynthesis- Mesophyll cells
Wound healing
78
Subtypes of parenchyma
Aerenchyma
Chlorenchyma
79
Collenchyma cells
Grouped in strands and help support young parts of the plant shoot
Thick and uneven non-lignifed primary cell walls
Lack secondary walls
Cells provide flexible support without restraining growth
Living at maturity
80
Sclerenchyma cells
rigid due to a thick secondary walls usually impregnated with lignin
Dead at functional maturity
Principal function is support
81
82
2 types of Sclerenchyma cells
Fibres
Sclereids
83
Fibres
Long and slender
Arranged in threads
84
Sclereids
Short and irregular in shape
Have thick lignified secondary walls
85
Indeterminate growth
A plant can grow throughout its life
86
Determinate growth
Some plant organs cease to grow at a certain size
87
Meristems
Perpetually embryonic tissue
Allow for indeterminate growth
88
Chlorenchyma
Chloroplasts present
89
Aerenchyma
Extensive air spaces
90
Primary growth
Apical meristems elongate shoots and roots
91
Secondary growth
Lateral meristems add thickness to woody plants
92
2 lateral meristems
Vascular (fascicular) cambium
Cork cambium
93
Vascular (fascicular) cambium
Adds layers of vascular tissue called secondary xylem (wood) and secondary phloem
94
Cork cambium
Replaces the epidermis with periderm, which is thicker and tougher
95
Which types of plants is secondary growth characteristic of
Gymnosperms
Many eudicots
NOT monocots
96
Secondary thickening
Occurs in shrubs, trees and may herbaceous plants
Initiated in the fascicular cambium
Results in additional xylem and phloem tissue being formed in rows
97
Lenticels
Allow gas exchange through the periderm
Found in cork surfaces
98
Where does root growth occur
Behind the root tip
In 3 zones of cells
99
Root cap
Covers root tip to protect the apical meristems as the root pushes through the soil
100
What does the primary growth of root produce
The epidermis, ground tissue and vascular tissue
101
Root anatomy of most eudicots
Xylem is star-like in appearance with phloem between the arms
102
Root anatomy of many monocots
A cor of parenchyma cells is surrounded by rings of xylem then phloem
103
Angiosperm roots
The stele is a vascular cylinder
104
Cortex
Ground tissue, mostly parenchyma cells,
Region between the vascular cylinder and epidermis
105
Endodermis
Innermost layer of cortex
Regulates passage of substances from the soil into the vascular cylinder
106
Growth categories- length of the life cycle
Annuals - life cycle in a year of less
Biennials- require 2 growing seasons
Perennials - live for many years
107
How to tell each year of growth
Bud scars
108
Growth rings - dendochronology
Age of plant
Rate of growth
Common in temperate climates
In woody species
109
What is in the centre of a Monocot root
Parenchyma
110
What is in the centre of a Eudicot root
Xylem and Phloem
111
Formation of lateral root
Form from within the pericycle
112
Order of ground tissue
Epidermis
Collenchyma
Parenchyma
Sclerenchyma
Vascular tissue
113
Annuals
Develop, flower, produce seed and die in one year
114
Biennials
Vegetative growth only in year one and lay down reserves
Copious production of seed in second year followed by senescence
115
Perennials
Lives for an indefinite period of time flowering and seeding at convenient times
116
117
Plant cell wall composition
Cellulose - 40-50%
Hemicellulose - 20-35%
Lignin 15-35%
118
Cellulose
A chain of beta glucose joined by covalent bonds
These form hydrogen bonds with other cellulose chains called fibrils
119
Deposition of hemicellulose
Binds layers of fibrils together
120
Lignin
Increases cell wall stiffness by promoting cross bonding of the cellulose fibrils
Prevent water from weakening the hydrogen bonds between cellulose molecules
As the plant lignifies it permits the plant to dispense with turgidity as a means of support (which leads to the reduction in the moisture content of mature stems)
121
Lignified tissues
Xylem
Sclerenchyma
122
How can plants vary the mechanical properties of the cell wall
Thickening- extra layers of cellulose
Deposition of lignin around the cellulose fibres
123
Main structural materials in plants
Cellulose
Lignin
Water
124
Is Collenchyma lignified
No
High degree of flexibility
Cellulose fibrils orientated along the length of cell allowing more flexibility
125
Mechanical stresses on plant
External from the wind
Internal from turgidity or transpiration
126
Stress
Force per unit area
N/m^2
127
Types of stress
Compression
Tensile
Shear - material deforms by slipping or shearing
128
Strain
The degree of deformation induced
Change in length over the original length (percentage)
129
Testing mechanical behaviour of plants
Tensile test
130
Stress strain curve
Breaking stress (strength) max= Max. Stress
The breaking strain (extensibility) max= Max. strain
Delta max is the maximum elongation
L is the origional length of the sample
PI r 2 or d/2 squared
dF/ddelta L/A
131
Strength
Maximum stress before the material fails
132
Stiffness
The amount of stress required to give a given strain
133
Young’s modulus (E)
The slope of the stress:strain curve
134
Breaking stress (strength)
Max stress
135
Breaking strain (extensibility)
Max strain
136
Free-standing upright stems
Regularly loaded both from the self weight and the wind
Windward side under tension
Leeward side under compression
137
How are upright stems adapted to withstand stresses
Distally arranged vascular bundles and Sclerenchyma fibres create a structure with a high tensile strength
Large turgid parenchyma cells resist compression
138
How is mechanical tissue arranged
Distally
As the plant gets older secondary thickening produces a complete ring of lignified secondary xylem- in eudicots
139
Why is lignified tissue stiff
Cells are long and thin and possess thick cell walls
Lignin helps stiffen the matrix by preventing the cellulose fibres from shearing past each other- due to helical arrangement of fibres
140
Preventing crack propagation
Stopped or prevented by fibres
141
Cantilever beam
Branches and petioles
Fixed at one end
Hangman’s gallows
142
Mechanical function of petioles
Tend to be channel-shaped in cross section
- allow twisting
-support leaf
Resist loading weight of the lead movement by the wind
Fibres and vascular tissue upper surface- resist tensile forces
Large parenchyma cells lower surface - resist compressive forces
143
Mechanical function of roots
Primary role in anchorage
144
Procumbent/ prostrate roots
Fibrous root systems
Prevent uprooting from ground- pulling
Tend to experience tensile forces from grazing animals
145
Free-standing upright plant roots
Require a rigid element - tap root
Lignified material found in the centre of the root + lateral roots
Strong in tension and stretches like a cable
Tap root is stiff in bending
146
Free-standing Monocot roots
Dense highly branching mat of roots
Rigid anchorage component
Adventitious root
Coronal root (cereal)
Prop root (maize)
147
Thigmomorphogenesis
The response to mechanical stimulation occurs naturally in plants as the shoot is moved by wind, rain, machinery and animals
A reduction in shoot primary growth (shorter)
An increase in secondary thickening
148
Thigmotropism
Response to contact with a solid object:
Coiling of tendrils around a support
Roots and objects
149
Shoot responses
The base of the shoots of stimulated plants are thicker than those from still plants.
Mechanism?
Existing rings of secondary thickening gets thicker in eudicots and tress
150
Root responses to mechanical stimulation
Mechanically stressed roots are thicker, stronger and stiffer than roots from stiff plants
151
Why do roots respond to physical stimuli
Increase in root strength also increases the anchorage strength of plants
152
Floral responses to pollinator sound
Flowers respond to pollinators sound within minutes by increasing nectar sugar concentration
153
Mechanism of plant response
Studies of plant defence responses shed light on signalling mechanisms
- Calcium (Ca2+) signalling pathways
- Plant hormones (Jasmonic acid and Gibberellins) thought to mediate response
