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Plant Physiology > Final exam > Flashcards

Final exam Flashcards

1
Q

Three ways light interacts with plants

A
  • Photosynthesis
  • Regulate growth and development
  • Lethal effects
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2
Q

Two ways light is used by plants

A
  • energy
  • information
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3
Q

Four ways light gives information

A
  • Quantity
  • Quality
  • Direction
  • Periodcity
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4
Q

What is the quality of light

A

balance of photons at different wavelengths

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5
Q

Most important spectral regions for plants

A

Red
Far Red
Blue

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6
Q

Factors that modify daylight

A

Cover
Elevation

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7
Q

If exposing lettuce seeds to red and far red light…

A

…the final light makes the decision

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8
Q

What is phytochrome

A

Photoreceptors that absorb red and far red light

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9
Q

What are photoreceptors

A

molecules used to detect sunlight

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10
Q

Red light _________ germentation and far red light ____________ it

A

Promotes, Inhibits

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11
Q

Some effects of red light

A
  • Promote germination
  • Promote De-etiolation
  • Inhibit stem elongation
  • Inhibit flowering
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12
Q

Two forms of phytochrome

A

Pr <—> Pfr

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13
Q

which form of phytochrome is physiologically active

A

Pfr

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14
Q

What makes Pr into Pfr

A

Red light

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15
Q

What does Pfr do in the plant

A

Induces synthesis of GA and Cytokinin and degrades ABA to allow germination

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16
Q

Phytochrome Pr and Pfr are ______________ dimer, consisting of a _______________ and a ________________

A

conformational
apoprotein
chromaphore

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17
Q

What is a chromophore

A

a light absorbing protein

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18
Q

What does the phytochrome apoprotein need in order to absorb red light

A

to be covalently linked to a chromophore

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19
Q

where is the chromophore attached on the apoprotein

A

cystine residue

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20
Q

Where is chromophore synthesized

A

plastids

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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
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22
Q

Where are phytochromes most concentrated

A

meristematic and recently meristematic regions

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23
Q

Two types of phytochrome

A

Type 1 - PhyA
Type 2 - Phys B-E

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24
Q

Which phytochrome degrades in light

A

Type I (PhyA)

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25
Q

Why does PhyA degrade in monocots

A

mRNA degredation

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26
Q

Two early steps in phytochrome action

A

Ion fluxes and altered gene expression

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27
Q

Main role of PhyA

A

sensing photosynthetic opportunity and extending the hypocotyl if buried or in low light
degrades when it hits the light

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28
Q

main role of PhyB

A

set up photosynthetic apparatus

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29
Q

Low red/far red ratios promote ________ and high red/far red ____________

A

elongation.
inhibit hypocotyl elongation.

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30
Q

Lack of germination due to environmental conditions

A

seed quiescence

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31
Q

lack of germination due to intrinsic factors

A

seed dormancy

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32
Q

two types of seed dormancy

A

primary and secondary

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33
Q

reasons for secondary dormancy

A

exposure to unfavorable conditions

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34
Q

reasons for exogenous dormancy

A
  • water impermeability
  • interference with gas exchange
  • mechanical constraint
  • retention of inhibitors
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35
Q

two types of primary dormancy

A

exogenous and endogenous

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36
Q

reason for endogenous dormancy

A

ratio of ABA:GA

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37
Q

Germination while still on the parent plant

A

vivipary - eg red mangrove

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38
Q

Chilling seeds to break dormancy

A

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.

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39
Q

Key enzyme for ABA biosynthesis in seed

A

NCED

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40
Q

if a seed lacks ABA biosynthesis it…

A

… can germinate early

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41
Q

Which two enzymes balance GA levels

A

GA2ox and GA3ox

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42
Q

Key protein in germination

A

DELLA, it represses germination
GA destroys it, ABA promotes it’s expression
DALLA is a switch

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43
Q

water potential for germination

A

mature seeds -50 to -300 MPa

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44
Q

Describe energy used for seed germination

A

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

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45
Q

what enhances transcription of amylase

A

GA - by binding to GID1 and breaking down DELLA (negative regulator)

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46
Q

what inhibits GA induced amylase transcription

A

ABA

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47
Q

what hormone stimulates cell division and suppresses growth of roots

A

cytokinin

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48
Q

If cytokinin is absent the plant will

A

have reduced apical and
shoot growth and enhanced
root growth

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49
Q

What hormone regulates growth in stems, coleoptiles and roots

A

Auxin

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50
Q

Which parts of the plant grow at lower auxin levels
higher

A

roots
stems

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51
Q

What are the two auxin receptors

A

ABP1 and TIR1

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52
Q

Enzyme induced by auxin for growth

A

Expansin

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53
Q

what conditions does expansin work in

A

acidic

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54
Q

how does auxin induce cell growth

A

more H+ moved to PM - expansin loosens polysaccharides

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55
Q

If no Auxin present what does IAA repressor do

A

inhibits ARF transcription

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56
Q

In the nucleus, what are the co-receptors for auxin

A

SCF and AUX repressor - both have partial binding site

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57
Q

What degrades ubiquitinated proteins

A

26S proteosome

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58
Q

What hormone induces gravitropism

A

auxin

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59
Q

what hormone induces root growth

A

auxin

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60
Q

how is auxin transported in the plant

A

polar, with gravity

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61
Q

what hormone promote shoot growth

A

cytokinin

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62
Q

what two hormones act antagonistically to regulate root and shoot growth

A

auxin and cytokinin

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63
Q

what hormone stimulates shoot growth in dwarf plants

A

GA - inc mitosis

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64
Q

which hormone induces cell elongation (expansin) without acidification

A

GA

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65
Q

which hormone induces vascular differentiation in seedlings

A

auxin

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66
Q

root hairs come from a ___________ cell

A

single

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67
Q

how many different patterns of growth does root epidermal development have

A

three

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68
Q

what hormone promotes growth of adventitious roots

A

auxin

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69
Q

what is needed to trigger growth of flowers in mature plants

A

photoperiod and temperature

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70
Q

three development phases of SAM

A

The juvenile phase
The adult vegetative phase
The adult reproductive phase

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71
Q

can a plant be induced to flower in the juvenile phase

A

no

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72
Q

Two stages in floral evocation

A

competence and determination

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73
Q

most important criterea for reaching adult stage

A

plant size

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74
Q

cold temp required for flowers

A

vernalization

75
Q

What happens if vernalization doesn’t occur

A

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
Q

where does vernalization occur

A

SAM

77
Q

best temps for vernalization

A

0-10C

78
Q

Does vernalization require the whole plant to be cold

A

no, just the SAM

79
Q

what does vernalization achieve

A

competence to flower

80
Q

does competence guarantee flowers?

A

no, correct photoperiod needed

81
Q

can vernalization be reversed

A

yes by heat, but longer cold exposure makes it mroe permanent

82
Q

5 stages of vernalization

A
  • Early period: active oxidation and phosphorylation
  • Dehydrogenase-dominated metabolism
  • Nucleic acid-related metabolism
  • Protein-related metabolism
  • Late period for stabilization of vernalization
83
Q

what is epigenetically modified during vernalization

A

FLC flowering repressor

84
Q

how is vernalization achieved molecularly

A

Demethylation of DNA

85
Q

what is photoperiod

A

the amount of time per day that a plant is exposed to light or darkness

86
Q

red light _______ flowering and far red light ______________ flowering

A

induces
inhibits

87
Q

what type of signaling pathway is used to induce flowering

A

long distance - leaf is site of photoperiod detection

88
Q

can flower inducing stimulus be ported with grafting

A

yes

89
Q

which hormone promote flowering

A

GA

90
Q

which plant family is ethylene the flower inducing hormone

A

pinnaply

91
Q

what is florigen

A

proposed flower inducing hormone - not confirmed

92
Q

what type of protein is FT flowering

A

globular

93
Q

what model is used for flower organ genes

A

ABC

94
Q

what determines pollen recognition

A

Recognition or rejection is determined by the pollen surface protein and stigma surface
protein.

95
Q

how long are pollen viable

A

varies from species to species - hours to weeks

96
Q

How pollen tubes know where to go when elongating

A

Ca2+ from the pollen tube will lead the tube to reach
embryo sac.

97
Q

which transcription factor regulates flowering and male fertility

A

GA-MYB

98
Q

what are the four stages of seed development

A
  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
Q

what are the hormones doing during seed development

A
  • 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
Q

when is seed desiccation tolerance obtained

A

late embryogenesis - when ABA levels highest

101
Q

what is the water potential of dry seeds

A

Mature seeds Ψw
can be -350 to -50 MPa

102
Q

what physical state is within a dry seed

A

glassy

103
Q

what protein inside a seed forms the glassy state

A

LEA protein

104
Q

which chemical is a precursor to vitamin A

A

Phytoene

105
Q

what are the three types of plant senescence

A
  • Programmed cell death (PCD)
  • Organ senescence
  • Whole plant senescence
106
Q

What are the two methods of Programmed Cell Death

A
  • Vacuole type
  • Hypersensitive response
107
Q

which Programmed cell death is in response to pathogens

A

hypersensitive response

108
Q

when are leafs senesced

A

Leaf senescence may be sequential, seasonal, or stress-induced

109
Q

what are the three phases of leaf senescence

A

Initiation phase
Degenerative phase
Terminal phase

110
Q

what pathway is required for chlorophyll breakdown (in senescence)

A

autophagy pathway

111
Q

what hormone triggers senescence

A

ethylene

112
Q

which hormones enhances senescence

A

ABA, SA and BR

113
Q

which hormone plays more role in flower senescence

A

JA

114
Q

Which hormone delays senescence

A

Cytokinin

115
Q

During leaf abscission the level of _________ decreases and the level of __________ increases

A

Auxin, ethylene

116
Q

What is the first line of defense for a plant

A

the surface, eg cuticle, trichomes etc

117
Q

What is the second line of defense for a plant

A

biochemical mechanisms

118
Q

What do trichomes do

A

release metabolites and send electrical signals to produce inducible compoounds

119
Q

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.

A

Phytolith

120
Q

Sharp calcium oxalate crystals

A

raphide

121
Q

secondary metabolites for defense

A

Terpenoids
Phenolics
Alkaloids

122
Q

which compounds make up resin

A

terpinoids

123
Q

what substance is made in laticifers

A

latex

124
Q

What part of the plant has higher levels of secondary compounds

A

young developing leaves

125
Q

which hormone activates defense responses and plays a role in insect resistance

A

Jasmonic acid

126
Q

what accumulates in the plant tissue quickly after wounding

A

Jasmonates

127
Q

what do plants produce in response to herbivory

A

proteinase inhibitors (PIs)

128
Q

How are proteinase inhibitors induces

A

jasmonate

129
Q

What do proteinase inhibitors do to insects

A

interfere with digestion - sicken or kill

130
Q

What do Herbivore-induced volatiles do

A

repel herbivores and attract natural enemies

131
Q

which hormone acts antagonistically to JA and reduces defense of herbivory

A

SA

132
Q

How does SA interfere with JA

A

NONEXPRESSER OF PR GENES1 (NPR1) is activated by SA, and interferes with JA signaling

133
Q

what is canavanie

A

a anti-nutritional compound to deter herbivores (non-protein AA - replaces Arg)

134
Q

3 anti-nutritional compounds

A

canavanine
lectins
protein inhibitors

135
Q

what do viruses rely on to infect plant

A

a break in the cell perimiter

136
Q

how are viruses normally transmitted to plants

A

insect vectors

137
Q

list some bacterial pathogen effects

A

rot
aberrant growth
toxins
plugging phloem or xylem

138
Q

important fungal pathogen

A

wheat rust
potato famine
black stem rust

139
Q

how do microbial pathogens enter the plant

A

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
Q

What do plants produce to fight pathogens

A

Phytoalexins - induced compounds

141
Q

Two antimicrobial enzymes

A

chitinase and glucanase

142
Q

post-translational protein

A

TaFLRS

143
Q

proteins that detect pathogens

A

R-proteins

144
Q

the plant ______ gene has to match the pathogen _____ gene for defense to be triggered

A

R, avr

145
Q

what is the hypersensitive response

A

killing of the cell and surrounding cells to halt spread of pathogen

146
Q

Early defense responses

A
  • Depolarization of membrane potential
  • Reactive Oxygen species
147
Q

what is system acquired defense

A

A single encounter with a pathogen may increase resistance to future attacks

148
Q

which hormone’s production is associated with disease resistance

A

SA

149
Q

what is Induced systemic resistance

A

Exposure to nonpathogenic
microorganisms (such as rhizobacteria) may increase resistance to future pathogen attack through development of induced systemic resistance

150
Q

what is the MAPK pathway

A

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
Q

abiotic stresses

A

physical or chemical

152
Q

Responses to stress

A

escape
tolerance
acclimatization
adaptation

153
Q

method of stress escape

A

complete lifecycle in non-stress times, eg ephemerals

154
Q

method of stress tolerance

A

alteration of morphological, physiological or metabolic response

155
Q

method of adaptation to stress

A

Adaptation involves genetic modification over many generations. heritable, eg thick cuticle

156
Q

acclimatization to stress

A

non-heritable but epigenetic, eg acquired cold-tolerance with inc exposure

157
Q

Dual role of reactive oxygen species (ROS) during abiotic stress

A
  1. Negative effect on plant growth and development.
  2. Positive effect by activating tolerance signaling.
158
Q

What gets elevated by stress which can regulate transcription by various mechanisms.

A

Ca2+

159
Q

which hormone helps with freezing-stress

A

cytokinin

160
Q

what temps can’t most plant tissues survive over

A

45

161
Q

why does heat harm plants

A

heat looses H-bonds which affects membrane composition

162
Q

what is produced under heat stress to protect proteins from unfolding

A

heat shock proteins

163
Q

Three main processes that can occur in the development of freezing tolerance:

A
  1. Stablilization of membranes
  2. Accumulation of sugars, other osmolytes, and antifreeze proteins.
  3. Multiple changes in gene expression
164
Q

what is anoxia

A

oxygen deficiency (flooding)

165
Q

2 groups on the basis of their response to high concentrations of salts

A

Halophytes
Glycophytes

166
Q

Three strategies for drought resistence

A

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
Q

first line of defense against drought

A

decrease leaf area

168
Q

second line of defense against
drought

A

deeper root growth

169
Q

3rd line of defense against drought

A

Stomata closure

170
Q

2 mechanisms mediating stomata closure

A
  • direct water loss in guard cells
  • loss of turgor due to inc water potential
171
Q

4th mechanism for drought

A

Limit photosynthesis within the chloroplasts

172
Q

5th response to drought

A

Increases wax deposition on the leaf surface

173
Q

genetic changes in response to drought

A
  • 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
Q

How do Plants adjust osmotically to drying soil

A

accumulating solutes
glycine and proline are compatible solutes

175
Q

what are compatible solutes

A

solutes that lower the water potential to bring in more water but don’t harm the plant

176
Q

two things that increase during osmotic stress

A

ABA and solute accumulation

177
Q

plant that can tolerate extreme dessication

A

resurrection plant

178
Q

ABA receptors which signal water stress

A

PYR/RCAR proteins
SnRK2 kinase active when ABA present

179
Q

More CPK activity =

A

more drought tolerant

180
Q

ABA _____________ in response to water stress

A

closes stomata

181
Q

Protoplasts are plant cells that are NOT

A

enveloped by the protective cell wall

182
Q

Protoplasts show _______ responses as intact whole plant tissues when responding to hormones, metabolites and environmental stimuli

A

similar

183
Q

Is a sterile technique used for studying protoplasts?

A

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
Q

What type of solution do protoplasts need to be kept in

A

isotonic

Plant Physiology (3 decks)

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