Final exam Flashcards
1
Q
Three ways light interacts with plants
A
- Photosynthesis
- Regulate growth and development
- Lethal effects
2
Q
Two ways light is used by plants
A
- energy
- information
3
Q
Four ways light gives information
A
- Quantity
- Quality
- Direction
- Periodcity
4
Q
What is the quality of light
A
balance of photons at different wavelengths
5
Q
Most important spectral regions for plants
A
Red
Far Red
Blue
6
Q
Factors that modify daylight
A
Cover
Elevation
7
Q
If exposing lettuce seeds to red and far red light…
A
…the final light makes the decision
8
Q
What is phytochrome
A
Photoreceptors that absorb red and far red light
9
Q
What are photoreceptors
A
molecules used to detect sunlight
10
Q
Red light _________ germentation and far red light ____________ it
A
Promotes, Inhibits
11
Q
Some effects of red light
A
- Promote germination
- Promote De-etiolation
- Inhibit stem elongation
- Inhibit flowering
12
Q
Two forms of phytochrome
A
Pr <—> Pfr
13
Q
which form of phytochrome is physiologically active
A
Pfr
14
Q
What makes Pr into Pfr
A
Red light
15
Q
What does Pfr do in the plant
A
Induces synthesis of GA and Cytokinin and degrades ABA to allow germination
16
Q
Phytochrome Pr and Pfr are ______________ dimer, consisting of a _______________ and a ________________
A
conformational
apoprotein
chromaphore
17
Q
What is a chromophore
A
a light absorbing protein
18
Q
What does the phytochrome apoprotein need in order to absorb red light
A
to be covalently linked to a chromophore
19
Q
where is the chromophore attached on the apoprotein
A
cystine residue
20
Q
Where is chromophore synthesized
A
plastids
21
Q
Steps in phytochrome activation
A
- POB attaches to GAF domain
- Conformational change (D-Ring rotates)
- Moves to nucleus - regulates gene expression
- some remains in cytosol
22
Q
Where are phytochromes most concentrated
A
meristematic and recently meristematic regions
23
Q
Two types of phytochrome
A
Type 1 - PhyA
Type 2 - Phys B-E
24
Q
Which phytochrome degrades in light
A
Type I (PhyA)
25
Why does PhyA degrade in monocots
mRNA degredation
26
Two early steps in phytochrome action
Ion fluxes and altered gene expression
27
Main role of PhyA
sensing photosynthetic opportunity and extending the hypocotyl if buried or in low light
degrades when it hits the light
28
main role of PhyB
set up photosynthetic apparatus
29
Low red/far red ratios promote ________ and high red/far red ____________
elongation.
inhibit hypocotyl elongation.
30
Lack of germination due to environmental conditions
seed quiescence
31
lack of germination due to intrinsic factors
seed dormancy
32
two types of seed dormancy
primary and secondary
33
reasons for secondary dormancy
exposure to unfavorable conditions
34
reasons for exogenous dormancy
- water impermeability
- interference with gas exchange
- mechanical constraint
- retention of inhibitors
35
two types of primary dormancy
exogenous and endogenous
36
reason for endogenous dormancy
ratio of ABA:GA
37
Germination while still on the parent plant
vivipary - eg red mangrove
38
Chilling seeds to break dormancy
stratification
5C 1-3 months in moist condition (sand). During stratification, starch, protein, lipid synthesis increases. Respiration lowers. Seed coat is softened and thus
increases the permeability.
39
Key enzyme for ABA biosynthesis in seed
NCED
40
if a seed lacks ABA biosynthesis it...
... can germinate early
41
Which two enzymes balance GA levels
GA2ox and GA3ox
42
Key protein in germination
DELLA, it represses germination
GA destroys it, ABA promotes it's expression
DALLA is a switch
43
water potential for germination
mature seeds -50 to -300 MPa
44
Describe energy used for seed germination
Carbohydrates (starches) - stored in amyloplasts in the endosperm of cereals. Degradation is mediated by α amylase and β amylase.
Gibberellins break down ALEURONE layer which induces amylase secretion
45
what enhances transcription of amylase
GA - by binding to GID1 and breaking down DELLA (negative regulator)
46
what inhibits GA induced amylase transcription
ABA
47
what hormone stimulates cell division and suppresses growth of roots
cytokinin
48
If cytokinin is absent the plant will
have reduced apical and
shoot growth and enhanced
root growth
49
What hormone regulates growth in stems, coleoptiles and roots
Auxin
50
Which parts of the plant grow at lower auxin levels
higher
roots
stems
51
What are the two auxin receptors
ABP1 and TIR1
52
Enzyme induced by auxin for growth
Expansin
53
what conditions does expansin work in
acidic
54
how does auxin induce cell growth
more H+ moved to PM - expansin loosens polysaccharides
55
If no Auxin present what does IAA repressor do
inhibits ARF transcription
56
In the nucleus, what are the co-receptors for auxin
SCF and AUX repressor - both have partial binding site
57
What degrades ubiquitinated proteins
26S proteosome
58
What hormone induces gravitropism
auxin
59
what hormone induces root growth
auxin
60
how is auxin transported in the plant
polar, with gravity
61
what hormone promote shoot growth
cytokinin
62
what two hormones act antagonistically to regulate root and shoot growth
auxin and cytokinin
63
what hormone stimulates shoot growth in dwarf plants
GA - inc mitosis
64
which hormone induces cell elongation (expansin) without acidification
GA
65
which hormone induces vascular differentiation in seedlings
auxin
66
root hairs come from a ___________ cell
single
67
how many different patterns of growth does root epidermal development have
three
68
what hormone promotes growth of adventitious roots
auxin
69
what is needed to trigger growth of flowers in mature plants
photoperiod and temperature
70
three development phases of SAM
The juvenile phase
The adult vegetative phase
The adult reproductive phase
71
can a plant be induced to flower in the juvenile phase
no
72
Two stages in floral evocation
competence and determination
73
most important criterea for reaching adult stage
plant size
74
cold temp required for flowers
vernalization
75
What happens if vernalization doesn't occur
plants that require vernalization show delayed flowering or remain vegetative. In many cases, these plants grow as rosettes with no elongation of the stem.
76
where does vernalization occur
SAM
77
best temps for vernalization
0-10C
78
Does vernalization require the whole plant to be cold
no, just the SAM
79
what does vernalization achieve
competence to flower
80
does competence guarantee flowers?
no, correct photoperiod needed
81
can vernalization be reversed
yes by heat, but longer cold exposure makes it mroe permanent
82
5 stages of vernalization
* Early period: active oxidation and phosphorylation
* Dehydrogenase-dominated metabolism
* Nucleic acid-related metabolism
* Protein-related metabolism
* Late period for stabilization of vernalization
83
what is epigenetically modified during vernalization
FLC flowering repressor
84
how is vernalization achieved molecularly
Demethylation of DNA
85
what is photoperiod
the amount of time per day that a plant is exposed to light or darkness
86
red light _______ flowering and far red light ______________ flowering
induces
inhibits
87
what type of signaling pathway is used to induce flowering
long distance - leaf is site of photoperiod detection
88
can flower inducing stimulus be ported with grafting
yes
89
which hormone promote flowering
GA
90
which plant family is ethylene the flower inducing hormone
pinnaply
91
what is florigen
proposed flower inducing hormone - not confirmed
92
what type of protein is FT flowering
globular
93
what model is used for flower organ genes
ABC
94
what determines pollen recognition
Recognition or rejection is determined by the pollen surface protein and stigma surface
protein.
95
how long are pollen viable
varies from species to species - hours to weeks
96
How pollen tubes know where to go when elongating
Ca2+ from the pollen tube will lead the tube to reach
embryo sac.
97
which transcription factor regulates flowering and male fertility
GA-MYB
98
what are the four stages of seed development
1. Embryogenesis - the embryo and extraembryonic tissues are formed.
2. Seed filling - storage materials accumulate and the seed grows.
3. Late maturation (desiccation) - the seed dries and the embryo becomes dormant.
4. Pod abscission
99
what are the hormones doing during seed development
- AUX present during all the seed development phases, auxin has a key role throughout the entire program of seed formation.
- CK is the opposite to auxin: a prominent role for cell divisions, but decrease during the maturation phase, when cell expansion prevails.
- BR follow the same pattern of CKs.
- GA is characteristic, two peaks: the stage of embryo differentiation, when the GAs promote cell growth and expansion, and the end of the maturation phase, when GAs activate proteolytic enzymes that mobilize resources in endosperm for germination.
- ABA shows an accumulation pattern complementary to the GAs, being the main hormone that inhibits all the processes induced by GAs.
100
when is seed desiccation tolerance obtained
late embryogenesis - when ABA levels highest
101
what is the water potential of dry seeds
Mature seeds Ψw
can be -350 to -50 MPa
102
what physical state is within a dry seed
glassy
103
what protein inside a seed forms the glassy state
LEA protein
104
which chemical is a precursor to vitamin A
Phytoene
105
what are the three types of plant senescence
- Programmed cell death (PCD)
- Organ senescence
- Whole plant senescence
106
What are the two methods of Programmed Cell Death
- Vacuole type
- Hypersensitive response
107
which Programmed cell death is in response to pathogens
hypersensitive response
108
when are leafs senesced
Leaf senescence may be sequential, seasonal, or stress-induced
109
what are the three phases of leaf senescence
Initiation phase
Degenerative phase
Terminal phase
110
what pathway is required for chlorophyll breakdown (in senescence)
autophagy pathway
111
what hormone triggers senescence
ethylene
112
which hormones enhances senescence
ABA, SA and BR
113
which hormone plays more role in flower senescence
JA
114
Which hormone delays senescence
Cytokinin
115
During leaf abscission the level of _________ decreases and the level of __________ increases
Auxin, ethylene
116
What is the first line of defense for a plant
the surface, eg cuticle, trichomes etc
117
What is the second line of defense for a plant
biochemical mechanisms
118
What do trichomes do
release metabolites and send electrical signals to produce inducible compoounds
119
What form in the epidermal cell walls and sometimes in the vacuoles, add toughness to the cell walls and make leaves hard for insects to chew.
Phytolith
120
Sharp calcium oxalate crystals
raphide
121
secondary metabolites for defense
Terpenoids
Phenolics
Alkaloids
122
which compounds make up resin
terpinoids
123
what substance is made in laticifers
latex
124
What part of the plant has higher levels of secondary compounds
young developing leaves
125
which hormone activates defense responses and plays a role in insect resistance
Jasmonic acid
126
what accumulates in the plant tissue quickly after wounding
Jasmonates
127
what do plants produce in response to herbivory
proteinase inhibitors (PIs)
128
How are proteinase inhibitors induces
jasmonate
129
What do proteinase inhibitors do to insects
interfere with digestion - sicken or kill
130
What do Herbivore-induced volatiles do
repel herbivores and attract natural enemies
131
which hormone acts antagonistically to JA and reduces defense of herbivory
SA
132
How does SA interfere with JA
NONEXPRESSER OF PR GENES1 (NPR1) is activated by SA, and interferes with JA signaling
133
what is canavanie
a anti-nutritional compound to deter herbivores (non-protein AA - replaces Arg)
134
3 anti-nutritional compounds
canavanine
lectins
protein inhibitors
135
what do viruses rely on to infect plant
a break in the cell perimiter
136
how are viruses normally transmitted to plants
insect vectors
137
list some bacterial pathogen effects
rot
aberrant growth
toxins
plugging phloem or xylem
138
important fungal pathogen
wheat rust
potato famine
black stem rust
139
how do microbial pathogens enter the plant
Some fungi have directly penetrate the cuticle and cell wall Other fungi, and also pathogenic bacteria, enter through natural openings such as stomata or through existing wounds caused by herbivores
140
What do plants produce to fight pathogens
Phytoalexins - induced compounds
141
Two antimicrobial enzymes
chitinase and glucanase
142
post-translational protein
TaFLRS
143
proteins that detect pathogens
R-proteins
144
the plant ______ gene has to match the pathogen _____ gene for defense to be triggered
R, avr
145
what is the hypersensitive response
killing of the cell and surrounding cells to halt spread of pathogen
146
Early defense responses
- Depolarization of membrane potential
- Reactive Oxygen species
147
what is system acquired defense
A single encounter with a pathogen may increase resistance to future attacks
148
which hormone's production is associated with disease resistance
SA
149
what is Induced systemic resistance
Exposure to nonpathogenic
microorganisms (such as rhizobacteria) may increase resistance to future pathogen attack through development of induced systemic resistance
150
what is the MAPK pathway
a chain of proteins in the cell that communicates a signal from a receptor on the surface of the cell to the DNA in the nucleus of the cell
151
abiotic stresses
physical or chemical
152
Responses to stress
escape
tolerance
acclimatization
adaptation
153
method of stress escape
complete lifecycle in non-stress times, eg ephemerals
154
method of stress tolerance
alteration of morphological, physiological or metabolic response
155
method of adaptation to stress
Adaptation involves genetic modification over many generations. heritable, eg thick cuticle
156
acclimatization to stress
non-heritable but epigenetic, eg acquired cold-tolerance with inc exposure
157
Dual role of reactive oxygen species (ROS) during abiotic stress
1. Negative effect on plant growth and development.
2. Positive effect by activating tolerance signaling.
158
What gets elevated by stress which can regulate transcription by various mechanisms.
Ca2+
159
which hormone helps with freezing-stress
cytokinin
160
what temps can't most plant tissues survive over
45
161
why does heat harm plants
heat looses H-bonds which affects membrane composition
162
what is produced under heat stress to protect proteins from unfolding
heat shock proteins
163
Three main processes that can occur in the development of freezing tolerance:
1. Stablilization of membranes
2. Accumulation of sugars, other osmolytes, and antifreeze proteins.
3. Multiple changes in gene expression
164
what is anoxia
oxygen deficiency (flooding)
165
2 groups on the basis of their response to high concentrations of salts
Halophytes
Glycophytes
166
Three strategies for drought resistence
Postponement: the ability to maintain tissue hydration
Tolerance: the ability to function while dehydrated.
Escape: complete life cycles during the wet season, before the onset of drought.
167
first line of defense against drought
decrease leaf area
168
second line of defense against
drought
deeper root growth
169
3rd line of defense against drought
Stomata closure
170
2 mechanisms mediating stomata closure
- direct water loss in guard cells
- loss of turgor due to inc water potential
171
4th mechanism for drought
Limit photosynthesis within the chloroplasts
172
5th response to drought
Increases wax deposition on the leaf surface
173
genetic changes in response to drought
- Synthesis and activity of aquaporin up-regulated
-seed proteins may protect vegetative tissues
- protease genes are induced to remove damaged proteins
- heat shock proteins induced
- reinforcement genes induced eg lignin
174
How do Plants adjust osmotically to drying soil
accumulating solutes
glycine and proline are compatible solutes
175
what are compatible solutes
solutes that lower the water potential to bring in more water but don't harm the plant
176
two things that increase during osmotic stress
ABA and solute accumulation
177
plant that can tolerate extreme dessication
resurrection plant
178
ABA receptors which signal water stress
PYR/RCAR proteins
SnRK2 kinase active when ABA present
179
More CPK activity =
more drought tolerant
180
ABA _____________ in response to water stress
closes stomata
181
Protoplasts are plant cells that are NOT
enveloped by the protective cell wall
182
Protoplasts show _______ responses as intact whole plant tissues when responding to hormones, metabolites and environmental stimuli
similar
183
Is a sterile technique used for studying protoplasts?
NO. A sterile technique is not necessary owing to the short incubation time in the protoplast
production phase or in the transient gene expression phase.
184
What type of solution do protoplasts need to be kept in
isotonic
