Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Botany > SU 1,2,3 > Flashcards

SU 1,2,3 Flashcards

(129 cards)

Start Studying
1
Q

Q: What are the two interconvertible forms of phytochrome and their respective light absorptions?

A

A: Pr absorbs red light (~660 nm) and converts to Pfr; Pfr absorbs far-red light (~730 nm) and converts back to Pr.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Q: Which form of phytochrome is biologically active and what does it trigger?

A

A: Pfr is the active form and it triggers gene expression for processes like seed germination and flowering.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Q: What is photoreversibility in plants?

A

A: It’s the reversible conversion between Pr and Pfr by red and far-red light, allowing plants to assess light quality and make developmental decisions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Q: How do COP1 proteins regulate photomorphogenesis in the dark vs. light?

A

A: In the dark, COP1 enters the nucleus to degrade light-promoting transcription factors. In light, it is inactivated and moves to the cytosol, allowing photomorphogenesis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Q: What light photoreceptors perceive blue light, and what are their roles?

A

A: Phototropins (phot1 and phot2) and cryptochromes. They mediate phototropism, stomatal opening, and flowering time.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Q: What are common responses to blue light in plants?

A

A: Phototropism, stomatal opening, inhibition of stem elongation, chloroplast movement, and circadian rhythm entrainment.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Q: How does light affect hypocotyl elongation?

A

A: Light inhibits elongation by degrading PIFs and inactivating COP1, promoting photomorphogenesis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Q: Which hormones antagonistically regulate seed dormancy and germination?

A

A: ABA maintains dormancy; GA promotes germination by inducing enzymes like α-amylase.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Q: What roles do FT and CO play in photoperiodic flowering?

A

A: CO activates FT under long-day light conditions. FT (florigen) moves to the SAM to trigger flowering.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Q: How does the circadian clock influence flowering in Arabidopsis?

A

The circadian clock makes the CO gene active at the right time during long days. Light keeps the CO protein from breaking down, so it can turn on the FT gene and make the plant flower.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Q: What is the external coincidence model in photoperiodism?

A

A: Flowering occurs only when the expression of flowering genes (e.g., CO or Hd1) coincides with light exposure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Q: What are the key pathways integrating flowering signals at the SAM?

A

A: Photoperiodic, vernalization, autonomous, and GA pathways converge on integrator genes like FT, SOC1, and LFY.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Q: What does DOG1 do in seed dormancy?

A

A: DOG1 stabilizes dormancy by promoting ABA signaling and repressing germination-related genes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Q: What are VLFR, LFR, and HIR in phytochrome responses?

A

A: Very Low Fluence Response, Low Fluence Response, and High Irradiance Response – describe light intensity thresholds for phytochrome activity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Q: What is florigen and where is it made?

A

A: Florigen is the flowering signal (FT protein), synthesized in leaves and transported to the shoot apical meristem.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Q: What is the role of phytochromes in seed germination under canopy shade?

A

A: Low R:FR ratio under canopy shade maintains Pr form, preventing germination by keeping phytochrome inactive.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Q: How does Pfr promote germination at the molecular level?

A

A: Pfr reduces ABA levels and promotes GA synthesis, which induces hydrolytic enzymes like α-amylase to mobilize food reserves.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Q: What are the three main types of seed dormancy?

A

A: Physical (impermeable coat), Physiological (hormonal control), Morphological (underdeveloped embryo).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Q: What does COP1 do in the dark?

A

A: COP1 enters the nucleus, forms complexes with SPA proteins, and targets positive photomorphogenesis regulators for degradation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Q: How do gibberellins (GA) promote flowering under short-day conditions?

A

A: GAs activate floral identity genes (LFY, SOC1) at the SAM, bypassing the need for CO/FT activation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Q: What are LEA proteins and what do they do?

A

A: Late Embryogenesis Abundant proteins protect cellular structures during seed desiccation by stabilizing macromolecules.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Q: How do plants use R:FR ratio to trigger shade avoidance?

A

A: Low R:FR is sensed by phytochrome B, promoting elongation and reduced leaf expansion to escape shade.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Q: What is florigen, and how does it work?

A

A: Florigen is the FT protein; it moves from leaves to the SAM and initiates flowering by forming a complex with FD.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Q: How does cold stratification affect seed dormancy?

A

A: Cold reduces ABA sensitivity and enhances GA synthesis, promoting dormancy release and germination.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q: What is the function of expansins in seed germination?
A: Expansins loosen cell walls near the radicle tip to allow radicle emergence by weakening endosperm resistance.
26
Q: How do ABA and GA interact to regulate dormancy and germination?
A: ABA promotes dormancy by suppressing GA; GA promotes germination by suppressing ABA, shifting the hormonal balance.
27
Q: What is the circadian clock’s role in flowering?
A: It times gene expression (like CO) so that light stabilizes key proteins under the right photoperiod, enabling flowering.
28
Q: How does light affect CO protein in Arabidopsis?
A: Light stabilizes CO protein during the day; darkness leads to its degradation, so flowering is promoted only under long days.
28
Q: What is the role of vernalization in flowering?
A: Vernalization silences FLC, a repressor of FT and SOC1, allowing flowering to proceed after cold exposure.
29
Q: What is the function of SOC1 in flowering?
A: SOC1 is a floral integrator that activates meristem identity genes like LFY and AP1 at the SAM.
30
Q: What is the role of PIFs in skotomorphogenesis?
A: PIFs (Phytochrome Interacting Factors) promote elongation by activating genes like XTH and EXP and are degraded in the light to allow photomorphogenesis.
31
Q: How do cryptochromes regulate flowering time?
A: Cryptochromes stabilize CO protein under blue light and modulate the circadian clock, promoting FT expression and flowering under long-day conditions.
32
Q: Describe the role of FMN chromophores in phototropins.
A: FMN chromophores absorb blue light, triggering conformational changes and autophosphorylation of phototropins, initiating downstream signaling for stomatal opening and phototropism.
33
Q: How does UVR8 function as a UV-B photoreceptor?
A: UV-B causes UVR8 to monomerize and interact with COP1–SPA1, promoting expression of UV-protective genes.
34
Q: What is the role of LEAFY (LFY) in flowering?
A: LFY is a meristem identity gene that initiates floral development by activating downstream genes involved in flower formation.
35
Q: How does the seed endosperm weaken during germination?
A: Through enzymatic breakdown of cell walls by expansins, PGs, PMEs, and glucanases, especially in the micropylar region.
35
Q: What is apical dominance and how is auxin involved?
A: Apical dominance suppresses lateral buds; auxin transported basipetally from the apex inhibits bud outgrowth.
36
Q: How do nitrate levels affect seed dormancy?
A: High nitrate reduces ABA sensitivity and promotes GA synthesis, helping break dormancy.
37
Q: What is the ecological function of bet-hedging via seed dormancy?
A: It spreads germination across years to reduce the risk of all seedlings failing in a bad season.
38
Q: What does PIN1 do in auxin transport?
A: PIN1 localizes to the basal membrane and directs downward auxin flow critical for root and vascular development.
39
Q: How do ABCB transporters enhance auxin movement?
A: They use ATP to actively export auxin and stabilize PIN proteins on the plasma membrane to maintain auxin flow.
40
Q: Describe the role of FT-FD complex in flowering.
A: FT protein moves to the SAM and binds FD; the complex activates genes like SOC1 and AP1 to initiate flowering.
41
Q: What experimental method measures endosperm weakening?
A: Puncture force tests quantify the mechanical resistance of the endosperm to radicle protrusion.
42
Q: What gene is epigenetically repressed during vernalization?
A: FLOWERING LOCUS C (FLC), a repressor of FT and SOC1.
43
Q: How do histone modifications affect seed dormancy?
A: Epigenetic marks like histone methylation repress GA biosynthesis genes, maintaining dormancy.
44
Q: What defines a long-day vs. short-day plant?
A: LDPs flower when days are longer than a critical length; SDPs flower when days are shorter.
45
Q: What are very low fluence responses (VLFRs)?
A: Light responses triggered by extremely low light levels; irreversible and often mediated by phyA.
45
Q: What does the DOG1 gene do?
A: DOG1 maintains seed dormancy by enhancing ABA signaling and stability of dormancy-related transcription factors.
46
Q: How does auxin enter and exit cells during polar transport?
A: Enters passively or via AUX1/LAX; exits via PIN and ABCB proteins, which are asymmetrically localized.
47
Q: Which photoreceptor mediates high irradiance responses (HIRs)?
A: Phytochrome A (phyA), especially under continuous far-red light.
48
Q: What is the function of the FT homolog Hd3a in rice?
A: It acts as florigen in rice, activated by Hd1 under short days and repressed under long days.
49
Q: What is the main floral repressor in Arabidopsis before vernalization?
A: FLC, which inhibits expression of FT and SOC1.
50
Q: How does light influence circadian clock entrainment?
A: Light signals perceived by photoreceptors reset the clock to synchronize internal rhythms with day-night cycles.
51
Q: What is the effect of ethylene in seed germination?
A: Ethylene can synergize with GA to promote endosperm weakening and counteract ABA.
52
Q: What is SOC1 and how is it regulated?
A: A floral integrator activated by FT, GA, and autonomous pathways to trigger floral meristem identity genes.
53
Q: What triggers CO mRNA peak in Arabidopsis?
A: The circadian clock ensures it peaks in the late afternoon—light must be present at this time for CO protein to accumulate.
54
Q: How does cold stratification affect gene expression?
A: It reduces ABA-responsive genes and increases GA biosynthetic and signaling gene expression.
55
Q: What role does APETALA1 (AP1) play in flowering?
A: AP1 defines floral meristem identity and initiates floral organ development in response to FT-FD-SOC1 signals.
56
Q: How do short-day plants like rice interpret photoperiod?
A: Hd1 activates florigen Hd3a under short days but represses it under long days, allowing precise control of flowering.
57
Q: Why can't sugar accumulation alone trigger flowering?
A: While sugars support growth, flowering depends on photoperiod-sensitive gene networks like CO-FT regulated by light and circadian cues.
58
Q: What red/far-red light response is seen in Lactuca sativa (lettuce) seeds?
A: Germination is promoted by red light (Pfr formation) and inhibited by far-red light (Pr), showing photoreversibility.
59
Q: Why do rice and Arabidopsis differ in photoperiodic response?
A: Arabidopsis is a long-day plant (LDP); rice is a short-day plant (SDP). Hd1 in rice can both activate or repress flowering based on day length.
59
Q: How is flowering in Arabidopsis thaliana regulated under long-day conditions?
A: The circadian clock times CO mRNA peak in the afternoon; light stabilizes CO protein, inducing FT and flowering.
60
Q: Which type of phytochrome mediates germination under very low light in Arabidopsis?
A: Phytochrome A (phyA), which is highly sensitive and triggers VLFR responses.
61
Q: Compare the stability of phyA and phyB under light.
A: phyA is rapidly degraded in light; phyB is stable and persists in active Pfr form.
61
Q: How does Oryza sativa (rice) respond to short days in terms of flowering?
A: Short days allow Hd1 to activate Hd3a (FT homolog), promoting flowering.
62
Q: What’s the difference in response to far-red light between phyA and phyB?
A: PhyA responds to continuous far-red (HIR); phyB is less responsive and focuses on LFR.
63
Q: What’s the role of GA in flowering of Arabidopsis under short days?
A: GA can bypass the photoperiod requirement by activating SOC1 and LFY at the SAM.
64
Q: How is qPCR used to study seed germination?
A: qPCR quantifies expression of genes like expansin, PG, or GA biosynthesis genes during radicle emergence.
65
Q: How are Arabidopsis mutants used to study photoreceptor function?
A: Mutants lacking phyA, phyB, or cryptochrome reveal their roles in light responses by observing altered development or germination.
66
Q: What experiment shows photoreversibility in seed germination?
A: Alternating red/far-red light pulses demonstrate reversible germination based on final light exposure.
67
Q: How does cold stratification affect ABA and GA levels in seeds?
A: It reduces ABA synthesis and promotes GA biosynthesis, shifting hormonal balance to favor germination.
68
Q: Compare flowering mechanisms in Arabidopsis vs. rice under the external coincidence model.
A: In Arabidopsis, CO protein must coincide with light. In rice, Hd1 activates or represses Hd3a depending on light duration.
69
Q: How can overexpression studies validate gene function?
A: Overexpressing genes like FT or LFY leads to early flowering, confirming their promotive roles.
70
Q: What effect do expansin mutants have on seed germination?
A: Reduced endosperm weakening and impaired radicle emergence due to stiffer cell walls.
71
Q: How is endosperm weakening spatially controlled?
A: Enzyme activity is localized to the micropylar region, where radicle emergence occurs.
72
Q: What evidence supports FT as florigen?
A: Grafting experiments show that FT protein produced in leaves can induce flowering in a non-flowering shoot apex.
73
Q: How do phototropins contribute to phototropism in Arabidopsis?
A: They detect blue light, autophosphorylate, and redirect auxin to the shaded side, causing differential growth.
74
Q: Compare the flowering signals in photoperiodic and gibberellin pathways.
A: Photoperiodic: FT as signal from leaves; GA pathway: GA moves to SAM and activates LFY/SOC1 directly.
74
Q: What is a key similarity between the vernalization and autonomous pathways?
A: Both repress FLC, lifting inhibition on FT and SOC1 to promote flowering.
75
Q: How do plants integrate light, hormones, and internal rhythms to decide when to grow, how to grow, and when to bloom? 🌸
Plants are master multitaskers. They: Use light signals (phytochromes, cryptochromes, phototropins) to detect day length, direction, and light quality Rely on hormones like ABA and GA to balance rest vs. growth — ABA keeps seeds sleeping, GA wakes them up Follow a circadian clock that synchronizes gene expression with sunrise and sunset Integrate all of this through key regulators (like CO, FT, SOC1, LFY) to trigger the perfect moment to flower 🌼 ✨This orchestra of signals lets plants grow smarter, not harder — making sure their energy, timing, and development are optimized for survival and success.
76
which are the floral identity genes?
EAFY (LFY) – Activates flower development by turning on floral organ identity genes. APETALA1 (AP1) – Works with LFY to establish floral meristem identity and initiates the formation of sepals and petals.
77
Q: Phototropism
A: Growth of a plant toward a light source, usually blue light.
78
Q: Photoreversibility
A: A reversible light response where red light promotes and far-red light inhibits processes like seed germination.
78
Q: Skotomorphogenesis
A: Growth in darkness with long hypocotyls, closed cotyledons, and an apical hook.
78
Q: Photomorphogenesis
A: Light-regulated development with short hypocotyls and expanded green cotyledons.
79
Q: Phytochrome
A: A red/far-red light receptor that controls germination, flowering, and shade avoidance.
80
Q: Cryptochrome
A: A blue-light receptor that helps regulate flowering and circadian rhythms.
81
Phototropin
A: A blue-light receptor that controls phototropism and stomatal opening.
82
Q: Abscisic Acid (ABA)
A: A hormone that keeps seeds dormant and helps them tolerate drying.
83
Q: Desiccation Tolerance
A: The ability of seeds to survive extreme drying using sugars and protective proteins.
84
Florigen
A: A mobile flowering signal (FT protein) that moves from leaves to the shoot meristem.
85
Q: Gibberellin (GA)
A: A hormone that promotes germination and flowering by triggering enzyme production and growth.
86
Q: CONSTANS (CO)
A: A transcription factor that turns on FT in long days to start flowering.
87
Q: FLOWERING LOCUS T (FT)
A: The gene that produces florigen, promoting flowering at the meristem.
88
Q: DOG1
A: A gene that helps keep seeds dormant by working with ABA.
89
Q: Polar Auxin Transport
A: One-way movement of auxin through the plant, guided by PIN and ABCB proteins.
90
Q: What does Pfr stand for?
A: Phytochrome far-red – the active form that promotes germination and photomorphogenesis.
91
Q: What does Pr stand for?
A: Phytochrome red – the inactive form that accumulates in darkness.
92
What does COP1 stand for?
A: Constitutive Photomorphogenesis 1 – a protein that suppresses light responses in darkness.
93
Q: What does SPA stand for?
A: Suppressor of Phytochrome A – proteins that partner with COP1 to block light signaling.
94
GA synthesis, which induces hydrolytic enzymes to mobilize food reserves
alpha-amylase
95
Q: What does FT stand for?
A: Flowering Locus T – the gene that encodes florigen to trigger flowering.
96
Q: What does LEA stand for?
A: Late Embryogenesis Abundant – proteins that protect cells during seed drying.
97
Q: What does CO stand for?
A: CONSTANS – a transcription factor that activates FT under long-day conditions.
98
Q: What does TOC1 stand for?
A: Timing of CAB Expression 1 – a core circadian clock gene expressed in the evening.
99
Q: What does LHY stand for?
A: Late Elongated Hypocotyl – a morning-expressed circadian clock gene.
100
What does CCA1 stand for?
A: Circadian Clock Associated 1 – a morning clock gene that represses TOC1.
101
Q: What does HY5 stand for?
A: Elongated Hypocotyl 5 – a transcription factor promoting light responses.
102
Q: What does FLC stand for?
A: Flowering Locus C – a repressor of flowering, silenced by vernalization.
103
Q: What does LFY stand for?
A: LEAFY – a floral meristem identity gene that promotes flower formation.
104
Q: What does SOC1 stand for?
A: Suppressor of Overexpression of CONSTANS 1 – integrates multiple flowering signals at the meristem.
105
Q: What triggers hypocotyl elongation in darkness?
A: High gibberellin and auxin levels, plus active PIFs and COP1 repressing light-responsive genes.
106
Q: What is the role of the FT protein?
A: It acts as florigen, moving from leaves to the shoot apical meristem to start flowering.
107
Q: How does red light affect seed germination?
A: Red light converts phytochrome to the active Pfr form, promoting germination.
108
Q: How does far-red light affect seed germination?
A: It converts Pfr back to Pr, the inactive form, inhibiting germination.
109
Q: What hormone promotes seed dormancy?
A: Abscisic acid (ABA).
110
Q: What hormone promotes seed germination?
A: Gibberellin (GA).
111
Q: What does the DOG1 gene do?
A: Maintains primary seed dormancy in coordination with ABA.
112
Q: What is florigen and where is it made?
A: A flowering signal (FT protein) made in leaves and transported to the shoot apex.
113
Q: What's the difference between phytochrome A (phyA) and phytochrome B (phyB) in light sensitivity?
A: phyA is highly sensitive to very low light; phyB needs higher light intensity to activate.
114
Q: How do phyA and phyB differ in stability?
A: phyA is unstable and degrades quickly in light; phyB is light-stable and persists in its active form.
115
Q: Which responses do phyA and phyB control?
A: phyA controls VLFR and HIR; phyB controls LFR (classic red/far-red reversible responses).
116
How do long-day and short-day plants differ in flowering triggers?
A: Long-day plants flower when days are long; short-day plants flower when nights are long.
117
How does CONSTANS (CO) function in Arabidopsis vs. Hd1 in rice?
A: In Arabidopsis, CO promotes flowering under long days; in rice, Hd1 promotes flowering under short days and represses it under long days.
118
Q: Compare CO mRNA and CO protein regulation.
A: CO mRNA is regulated by the circadian clock; CO protein is stabilized by light and degraded in darkness.
119
What’s the functional difference between FT and SOC1?
A: FT is a mobile flowering signal (florigen); SOC1 is a meristem-local integrator activated by FT.
120
Q: How does ABA affect germination vs. GA?
A: ABA maintains dormancy and blocks germination; GA breaks dormancy and promotes germination.
121
Q: How do DOG1 and FT differ in function?
A: DOG1 promotes seed dormancy; FT promotes flowering.

Botany (2 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions