5: Plant-Environment Interactions Flashcards
Module 1, Lesson 5
1
Q
Certain ____ molecules in plants can absorb light and initiate a response.
A
Pigment
2
Q
____ is a pigment that helps plants perform photosynthesis.
A
Chlorophyll
3
Q
____ is a directional growth response to light.
A
Phototropism
4
Q
____ is nondirectional plant development triggered by light.
A
Photomorphogenesis
5
Q
The biologically inactive version of phytochrome is…
A
Phytochrome red
(Pr)
6
Q
When red photons are available, Pr is converted to…
A
Pfr
7
Q
The biologically active version of phytochrome is…
A
Phytochrome far-red
(Pfr)
8
Q
____ facilitates expression of light-response genes and promotes a plant response.
A
Pfr
9
Q
When no far-red photons are available, Pfr converts to…
A
Pr
10
Q
When a plant is exposed to direct sunlight…
A
Pr converts to Pfr
11
Q
In the absence of direct sunlight…
A
Pfr converts to Pr
12
Q
In order to regulate its concentration in the plant, Pfr is degraded by…
A
Proteosomes
13
Q
True or false:
Light-response genes are continually expressed in the plant.
A
False
14
Q
List the two mechanisms by which Pfr can activate light-response genes.
A
- Directly regulating gene expression
- Acting through kinase
15
Q
In order to directly regulate gene expression, Pfr…
A
Enters the nucleus and interacts with the DNA
16
Q
Pfr can indirectly regulate gene expression by working through the protein…
A
Kinase
17
Q
When Pfr works through kinase, a kinase signal pathway will eventually activate…
A
Transcription factors
18
Q
List three plant growth responses that can be influenced by phytochrome.
A
- Seed germination
- Shoot elongation
- Rapid elongation
19
Q
____ is inhibited by far-red light and stimulated by red light.
A
Seed germination
20
Q
____ is a shoot response found in seedlings that grow in the dark.
A
Etoliation
21
Q
____ conserves a seedling’s energy while allowing it to grow towards the light.
A
Etoliation
22
Q
Once exposed to light, a seedling that sprouted in the dark will…
A
Assume its normal morphology
23
Q
Under shady conditions, a plant will…
A
Rapidly increase in height
24
Q
In crowded conditions, a plant will ____ to outcompete its neighbors.
A
Elongate rapidly
25
Stems are normally ____ to blue wavelengths.
Positively phototropic
26
# True or false:
Roots are normally positively phototropic.
False
They will either have no phototropic response or exhibit a weak negative response.
27
Phototropins 1 and 2 are ____ light receptors.
Blue
28
____ is a plant hormone involved in phototropic growth.
Auxin
29
Shoots tend to bend towards light in order to...
Increase exposure to light for photosynthesis
30
____ are 24-hour cycle rhythms that often affect leaf position.
Circadian clocks
31
____ is the response of plant's to Earth's gravitational field.
Gravitropism
32
Roots are ____ gravitropic.
Positively
33
Roots will usually bend ____ the center of gravity.
Towards
34
In roots, the gravity-sensing region is located in the...
Root cap
35
Stems are ____ gravitropic.
Negatively
36
Stems usually bend ____ the center of gravity.
Away from
37
In stems, the gravity-sensing region is located in the...
Endodermal cells surrounding vascular tissue
38
____ are starch-containing plastids that may be involved in sensing gravity.
Amyloplasts
39
Amyloplasts sink in response to...
Gravitational fields
40
____ is responsible for transmitting signals from the gravity-sensing cells to the rest of the plant.
Auxin
41
In shoots, auxin promotes greater elongation of cells on the...
Lower side of the stem
42
In roots, auxin promotes greater elongation of cells on the...
Upper side of the root
43
List three main plant responses to mechanical stimuli.
1. Thigmomorphogenesis
2. Thigmotropism
3. Reversible responses to touch
44
____ occurs when a plant permanently changes form in response to mechanical stimuli.
Thigmomorphogenesis
45
____ is directional growth in response to contact.
Thigmotropism
46
Plants that grow by twining around other objects exhibit...
Thigmotropism
47
Many reversible responses to touch involve changes in...
Turgor pressure
48
____ are clusters of cells at the base of a leaf that change turgor pressure in response to contact.
Pulvini
49
Extreme conditions may promote ____ in a plant.
Dormancy
50
The process of dormancy begins with ____ of plant organs.
Abscission
51
The cellular changes involved in abscission take place in the...
Abscission zone
52
A suberin-impregnated ____ is located on the stem side of the abscission zone.
Protective layer
53
A ____ is located on the organ/leaf side of the abscission zone.
Separation layer
54
Seed dormancy is typically caused by...
Drought conditions
55
____ is a plant hormone that is instrumental in causing and maintaining seed dormancy.
Abscisic acid
(ABA)
56
# True or false:
As in animals, plant hormones are chemical signal molecules.
True
57
# True or false:
Unlike in animals, plant hormones are not produced in special tissues.
True
58
List the eight major types of plant hormones.
1. Auxin
2. Cytokinins
3. Ethylene
4. Abscisic acid
5. Gibberellins
6. Brassinosteroids
7. Oligosaccharins
8. Strigolactones
59
____ was one of the first hormones to be discovered.
Auxin
60
____ is a plant hormone that makes cell walls soft to enable expansion and elongation.
Auxin
61
Auxin is produced in the...
Shoot tip
(apical meristem)
62
In a phototropic response, ____ migrates to the dark side of the stem and promotes elongation there.
Auxin
63
Synthetic auxin is sometimes used as...
Herbicides
64
____ are a plant hormone that promote cell division and differentiation.
Cytokinins
65
Cytokinins are produced in the...
Root tip
66
Cytokinins sometimes act in opposition to...
Auxin
67
____ promote growth of lateral buds in shoots.
Cytokinins
68
____ suppresses growth of lateral buds in shoots, a process known as apical dominance.
Auxin
69
____ inhibit lateral root formation.
Cytokinins
70
____ promotes lateral root formation.
Auxin
71
____ is the only gaseous plant hormone.
Ethylene
72
____ has a major role in promoting fruit development and ripening.
Ethylene
73
The production of ethylene is stimulated by the release of ____ in developing fruits.
Auxin
74
____ is a plant hormone involved in abscission.
Ethylene
75
____ slows fruit ripening.
Carbon dioxide
76
In order to break dormancy, the levels of ____ must decrease.
Abscisic acid
77
____ can counteract the effects of other hormones, such as auxin and gibberellins.
Abscisic acid
78
____ influences the opening and closing of stomata.
Abscisic acid
79
____ are a class of 100+ hormones important in stem elongation and flowering.
Gibberellins
80
Gibberellins often work in conjunction with...
Auxin
81
____ are plant hormones with wide effects on plant growth, reproductive development, and delaying senescence.
Brassinosteroids
82
____ are plant hormones involved in defense signaling and organ development.
Oligosaccharins
83
____ are formed from the breakdown of oligosaccharides by pathogens.
Oligosaccharins
84
____ are plant hormones that work with auxin and cytokinin to help shape plants.
Strigolactones
85
____ are derived from carotenoid hormones.
Strigolactones
86
____ are a major reproductive advantage for angiosperms.
Flowers and fruits
87
____ is the ability to reproduce (produce fruits and flowers).
Competency
88
Internal signals and environmental cues can turn on reproductive genes that specify...
Formation of flower structures
89
The process of becoming competent is called a...
Phase change
90
During phase change, the plant...
Gains the ability to flower
(transitions from juvenile to adult)
91
# True or false:
Once phase change occurs, the plant will begin to flower.
False
Sometimes other factors are needed to trigger flowering
92
List the four genetically-regulated pathways involved in flower production.
1. Light-dependent
2. Temperature-dependent
3. Gibberellin-dependent
4. Autonomous
93
Which two pathways involved in flower production are triggered by external cues?
1. Light-dependent
2. Temperature-dependent
94
Which two pathways involved in flower production are triggered by internal mechanisms?
1. Gibberellin-dependent
2. Autonomous
95
The ____ is an adaptation to changing seasons that enables plants to flower at the proper time.
Photoperiodic response
96
The ____, also known as "day length" is the proportion of light to dark in a 24-hour cycle.
Photoperiod
97
# True or false:
Plants using the light-dependent pathway respond to the amount of uninterrupted darkness.
True
98
Long-day plants will flower when....
The dark period is short
99
Long-day plant species will flower when the amount of darkness ____ a critical length for that species.
Is less than
100
What time of the year do long-day plants tend to flower?
Between late spring and early summer
101
Short day plants will flower when...
The dark period is long
102
Short-day plant species will flower when the amount of darkness ____ a critical length for that species.
Exceeds
103
What time of year do short-day plants tend to flower?
Between late summer and early fall
104
Interrupting the dark period with light...
Interrupts the plant response
105
In ____ plants, the photoperiod requirement is not absolute and other factors play a role in flowering.
Facultative
106
List four advantages of photoperiodic flowering control.
1. Ensures abiotic conditions are optimal
2. Synchronizes flowering with pollinator availability
3. Helps minimize competition for resources
4. Helpful for commercial growers
107
____ is a period of chilling needed for some plants to flower and some seeds to germinate.
Vernalization
108
Using the temperature-dependent pathway ensures that...
Flowering occurs after a cold period
109
Using the gibberellin-dependent pathway, flowering requires...
An increase in gibberellin levels
110
Using the ____ pathway, flowering doesn't depend on any external cues except nutrition.
Autonomous
111
List two genes that determine flowering regardless of pathway.
1. LEAFY (LFY)
2. APETALAI (API)
112
Three pathways use genes that...
Either repress or promote flower development
113
The gibberellin-dependent pathway can directly influence the expression of...
LFY genes
114
The ligh-dependent pathway uses a protein that acts as a...
Transcription factor, to turn on other genes
