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Hormone definition
1.Transported to site of activity
2.Interact with specific cell receptor proteitns
3.Effect physiological activity at very low concentrations
Classic Hormones
Auxins
-Gibberellins
-Cytokinins
-Ethylene
-Abscisic Acid (ABA
Auxin
indole ring, 2 part ring , indole derived from tryptopan

Synthesis: - tryptopan dependent or tryptophan-independent
Tryptophan independent used w/ shikimic acid pathway
Acid growth hypo thesis
Auxin promotes proton extrusion by “activation” of H-ATPases
-lowering apoplastic pH activates wall- loosening proteins
-Auxin promotes synthesis of more H-ATPases, cell wall proteins
DR5
GUS
an auxin responsive element so turned on when auxin is present
is an enzyme produced by bacteria not found in plants and produces a color
Developmental effects of auxin
1. Regulates Apical dominance (ex. Pine trees) one dominant shoot (trunk)
2. Promotes lateral root formation (2ndary roots)
3. Delays leaf Abscission
4. Promotes vascular differentiation
5. Promotes fruit development
Applied uses of auxins
Rooting of cuttings
Prevention of fruit and leaf drop in animals
Herbicides (2-4D)
Gibberellin sturccture

Giberellic acid (GA3) Isolated from

Gibberellin A1 (GA1) isolated from
(diterpene acids) based on 20 Carbons

bean sead in 1958
gibberella (1930’s)
Physiological effects of gibberellins
1. Stimulates stem growt in dwarf and rosette plants
2. Transition from juvenile to adult phases
3. Floral initiation/ sex determination
4. Fruit set
Promote seed germination
Commercial Applications- Gibberellins
Fruit Production
1.malting of barley
2.Increase sugarcane yields
3.Plant Breeding
4.Gibberellins synthesis inhibitors: minimize elongation growth
Gibberellin Detection
Analytical method of choice
Bioassay
1. Analytical method of choice
: can identify hormone and quantify how much is in the tissure
-HPLC (high-performance liquid chromatography)
-GC-MS (gas chromatography, mass spectrometry
2. Bioassay
Dwarf rice leaf sheath elongation
-Barley aleurone, a-amylase stimulation
Gibberellin Synthesis
Stage 1: (plastid) GGPP (geranylgeranyl pyrophosphate)  ent-Kaurene
Stage 2: (ER) ent-Kaurene GA53
Stage 3: (cytosol) GA53 GA1 and other GA’s
Approximately how many different GA’s are there?
over 125 GA’s
Describe the effect of GA’s on stem growth and bolting in rosette plants like cabbage
a. Increase stem length, bolting (certain species flower)

Cabbage plants are long day plants once days get longer they begin to bolt. Short warm day with added gibberellins acid to replace long day and they begin to bolt
GA effects the transition from juvenile to adult phases in at least some plants. Describe two examples where this is the case.
-edera helix (ivy) reversion to juvenile (GA3). When plant is young there is bigger lobed leaves. And when mature it looks like one single leaf and is not lobed. Add growing tip of mature plant it will switch to juvenile form and lobe again.

-conifers advance to reproduction (ga4 + ga7) doesn’t make pinecones until in adult phase but can be onverturned by adding both ga’s and it makes cones and goes through reproduction much earlier
How does GA effect fruit set? Give an example
a. Stimulates fruit set in animals- after pollination occurs we start to get fruit but there is some flowers that don’t make fruit but adding gibberellins formation of fruit will increase
How do gibberellins affect seed germination? What are two examples of these effects?
a. Overcome dormancy in certain seeds requiring light or cold.
b. Stimulate hydrolases (a-amylase) in germinating cereal seeds. When they germinate they break down a large vol. of starch in the seed by hydrolases which are stimulated by gibberellins
Where does gibberellin synthesis occur in plants?
in Apical tissures

Growing buds, leaves and upper internodes (also immature seeds and fruits)
What do the Le and Na genes code for in peas?
GA1 and tallness
What are the genotypes of peas that have "dwarf" and "ultra-dwarf" phenotypes?
na na______
na na Le le or na na le le
What is the reason that ultra-dwarf is even shorter than dwarf?
(no ga’s
epistasis)
In ultra dwarf there is block btw ent-kaurene and ga12 aldehyde
(stage 2)
Who discovered kinetin and what is the effect of this compound on callus tissue?
Carlos Miller (Folke Skoog) discovered kinetin stimulates cell division in tobacco callus
Describe where GA is synthesized in a germinating seed. Where is the GA active in a germinating seed? What does the activity of GA ultimately produce in the embryo?
1. embryo synthesizes ga1, released to starchy endosperm
2. Ga diffuses to aleurone layer surrounding endosperm
3. Aleurone cells synthesize and secrete a-amylase and other hydrolases into starchy endosperm
4. Starch and other molecules broken down and solubilized
5. Solutes are transported to embryo
What is an aminopurine ring and how is it related to cytokinin structure?
on carbon 6 there is a ring structure, has an aminopurine ring (basic part of cytokinins).
What is the most common, naturally occurring cytokinin? Who discovered this cytokinin?
Letham and Miller discover zeatin, naturally occurring cytokinin
Where does cytokinin synthesis occur in a higher plant?
synthesis in root meristems
What are ribotides and ribosides? How are they synthesized?
ribotides (+ ribose sugar phosphate )& ribosides (+ ribose sugar)

Ribotide riboside (so remove phosphates) --> free base cytokinin
Generally, how is zeatin synthesized from ribotides and ribosides?
ATP/ADP + DMAPP ------> iPTP/iPDP (isopentenyl transferase; IPT) -->-->--> ZR (zeatin riboside)
What are the substrates for the reaction catalyzed by cytokinin oxidase? Why is the enzyme important?
iP via cytokine oxidase + O2  adenine + 3 methyl 2-butenal
Transforming tobacco plants to overexpress cytochrome oxidase produces stunted, dwarf-like plants. What would be the logical reason for this altered phenotype?
break down cytokinins more rapidly so is smaller
What are thought to be the roles of auxin and cytokinin in controlling lateral bud activity and apical dominance?
auxin inhibits lateral bud formation
-addition of cytokinin to lateral bud overcomes inibition
Cytokinins delay leaf senescence. How is this effect related to leaf nutrient content?
programmed aging
What is the effect of zeatin on cell expansion in leaves and cotyledons?
How does light modify the effect of zeatin?
put radish cotyledons in dark and light. In dark they grow but don’t get green.
In the light they get green. If they put in solution of zeatin. In dark they still have no color but is bigger. In light a light green but bigger.
What are five ways that overexpression of isopentenyl transferase (IPT) modifies the phenotype of a plant like tobacco?
More leaves from shoot apical meristem are produced
-Leaves have more chlorophyll
-Leaf senescence retarded so last a long time and resist falling yellow and falling off
-Apical dominance reduced. Which can be overcome by cytokinins
-Rooting of cuttings reduce; root growth rate reduced
How is the gall synthesized? What role does cytokinin play in this process?
1. Infecion by soil bacterium, Agrobacterium tumefaciens
2. Gall is formed by plant cells de-differentiating, dividing and producing tumor

cytokinins (ipt), regulate tumor growth
How has crown gall infection been modified to provide a mechanism for transforming plants?
Did plant transformation using ti plasmid from agrobacterium
1. Removed tdna from plasmid
2. Engineer ti plasmid
3. Re-introduce engineered plasmid
4. Infect plant tissure-cultrue cells
5. Select transformed plant cells
6. Regenerate transformed plants
Draw the structure of ethylene. What did M. Jagger and K. Richards say that applied to ethylene?
?
Describe the synthesis of ethylene by plants and include the roles of ACC synthase and ACC oxidase. What factors stimulate the activity of each of these enzymes
Methionine (sulfur) + ATP S-adenosyl methionine (SAM) + Ppi + Pi  *ACC and methionine recycled in Yang Cycle (+o2) via ACC oxidase  C2H4

*1-aminocyclopropane-1-carboxylic acid
What is the climacteric response in plants?
rise in respiratory rate with ripening
List several plants that produce climacteric fruit and several that do not.
?
How were the transformed tomato plants modified and how have these plants provided evidence that links ripening to ethylene
ACC sythase, anti sense construct. Which is make a gene and take it out and change the orientation of it and put it back it, which results in it going back. This messes up synthesis 1 of that gene and cause other genes like it to inactivate so they can’t make products. So this elimates all synthesis of acc synthase. So tomato is green and don’t get ripe.
What is epinasty and how is it related to ethylene production and flooding?
downward curvature of leaves (uneven elongation of petiole). On the top of petiole cells expand more on top than on bottom. SAM  ACC ethylene but when flooded we get anoxia and blocks the activity of the oxidase and get a build up of ACC. This ACC is carried up vascular tissue where oxygen is present so at top there is ethylene
What is aerenchyma tissue?
-gas diffusion to flooded roots through arenchyma so diffusion is more rapid and allows minimal respiration to sustain the plant.
Describe the effect of GA’s on stem growth and bolting in rosette plants like cabbage
a. Increase stem length, bolting (certain species flower)

Cabbage plants are long day plants once days get longer they begin to bolt. Short warm day with added gibberellins acid to replace long day and they begin to bolt
GA effects the transition from juvenile to adult phases in at least some plants. Describe two examples where this is the case.
-edera helix (ivy) reversion to juvenile (GA3). When plant is young there is bigger lobed leaves. And when mature it looks like one single leaf and is not lobed. Add growing tip of mature plant it will switch to juvenile form and lobe again.

-conifers advance to reproduction (ga4 + ga7) doesn’t make pinecones until in adult phase but can be onverturned by adding both ga’s and it makes cones and goes through reproduction much earlier
How does GA effect fruit set? Give an example
a. Stimulates fruit set in animals- after pollination occurs we start to get fruit but there is some flowers that don’t make fruit but adding gibberellins formation of fruit will increase
How do gibberellins affect seed germination? What are two examples of these effects?
a. Overcome dormancy in certain seeds requiring light or cold.
b. Stimulate hydrolases (a-amylase) in germinating cereal seeds. When they germinate they break down a large vol. of starch in the seed by hydrolases which are stimulated by gibberellins
Where does gibberellin synthesis occur in plants?
in Apical tissures

Growing buds, leaves and upper internodes (also immature seeds and fruits)
What do the Le and Na genes code for in peas?
GA1 and tallness
What are the genotypes of peas that have "dwarf" and "ultra-dwarf" phenotypes?
na na______
na na Le le or na na le le
What is the reason that ultra-dwarf is even shorter than dwarf?
(no ga’s
epistasis)
In ultra dwarf there is block btw ent-kaurene and ga12 aldehyde
(stage 2)
Who discovered kinetin and what is the effect of this compound on callus tissue?
Carlos Miller (Folke Skoog) discovered kinetin stimulates cell division in tobacco callus
Describe where GA is synthesized in a germinating seed. Where is the GA active in a germinating seed? What does the activity of GA ultimately produce in the embryo?
1. embryo synthesizes ga1, released to starchy endosperm
2. Ga diffuses to aleurone layer surrounding endosperm
3. Aleurone cells synthesize and secrete a-amylase and other hydrolases into starchy endosperm
4. Starch and other molecules broken down and solubilized
5. Solutes are transported to embryo
What is an aminopurine ring and how is it related to cytokinin structure?
on carbon 6 there is a ring structure, has an aminopurine ring (basic part of cytokinins).
What is the most common, naturally occurring cytokinin? Who discovered this cytokinin?
Letham and Miller discover zeatin, naturally occurring cytokinin
Where does cytokinin synthesis occur in a higher plant?
synthesis in root meristems
What are ribotides and ribosides? How are they synthesized?
ribotides (+ ribose sugar phosphate )& ribosides (+ ribose sugar)

Ribotide riboside (so remove phosphates) --> free base cytokinin
Generally, how is zeatin synthesized from ribotides and ribosides?
ATP/ADP + DMAPP ------> iPTP/iPDP (isopentenyl transferase; IPT) -->-->--> ZR (zeatin riboside)
What are the substrates for the reaction catalyzed by cytokinin oxidase? Why is the enzyme important?
iP via cytokine oxidase + O2  adenine + 3 methyl 2-butenal
Transforming tobacco plants to overexpress cytochrome oxidase produces stunted, dwarf-like plants. What would be the logical reason for this altered phenotype?
break down cytokinins more rapidly so is smaller
What are thought to be the roles of auxin and cytokinin in controlling lateral bud activity and apical dominance?
auxin inhibits lateral bud formation
-addition of cytokinin to lateral bud overcomes inibition
Cytokinins delay leaf senescence. How is this effect related to leaf nutrient content?
programmed aging
What is the effect of zeatin on cell expansion in leaves and cotyledons?
How does light modify the effect of zeatin?
put radish cotyledons in dark and light. In dark they grow but don’t get green.
In the light they get green. If they put in solution of zeatin. In dark they still have no color but is bigger. In light a light green but bigger.
What are five ways that overexpression of isopentenyl transferase (IPT) modifies the phenotype of a plant like tobacco?
More leaves from shoot apical meristem are produced
-Leaves have more chlorophyll
-Leaf senescence retarded so last a long time and resist falling yellow and falling off
-Apical dominance reduced. Which can be overcome by cytokinins
-Rooting of cuttings reduce; root growth rate reduced
How is the gall synthesized? What role does cytokinin play in this process?
1. Infecion by soil bacterium, Agrobacterium tumefaciens
2. Gall is formed by plant cells de-differentiating, dividing and producing tumor

cytokinins (ipt), regulate tumor growth
How has crown gall infection been modified to provide a mechanism for transforming plants?
Did plant transformation using ti plasmid from agrobacterium
1. Removed tdna from plasmid
2. Engineer ti plasmid
3. Re-introduce engineered plasmid
4. Infect plant tissure-cultrue cells
5. Select transformed plant cells
6. Regenerate transformed plants
Draw the structure of ethylene. What did M. Jagger and K. Richards say that applied to ethylene?
?
Describe the synthesis of ethylene by plants and include the roles of ACC synthase and ACC oxidase. What factors stimulate the activity of each of these enzymes
Methionine (sulfur) + ATP S-adenosyl methionine (SAM) + Ppi + Pi  *ACC and methionine recycled in Yang Cycle (+o2) via ACC oxidase  C2H4

*1-aminocyclopropane-1-carboxylic acid
What is the climacteric response in plants?
rise in respiratory rate with ripening
List several plants that produce climacteric fruit and several that do not.
?
How were the transformed tomato plants modified and how have these plants provided evidence that links ripening to ethylene
ACC sythase, anti sense construct. Which is make a gene and take it out and change the orientation of it and put it back it, which results in it going back. This messes up synthesis 1 of that gene and cause other genes like it to inactivate so they can’t make products. So this elimates all synthesis of acc synthase. So tomato is green and don’t get ripe.
What is epinasty and how is it related to ethylene production and flooding?
downward curvature of leaves (uneven elongation of petiole). On the top of petiole cells expand more on top than on bottom. SAM  ACC ethylene but when flooded we get anoxia and blocks the activity of the oxidase and get a build up of ACC. This ACC is carried up vascular tissue where oxygen is present so at top there is ethylene
What is aerenchyma tissue?
-gas diffusion to flooded roots through arenchyma so diffusion is more rapid and allows minimal respiration to sustain the plant.
What are the characteristics of an etiolated seedling, a seedling that develops in the dark?
elongated stems (internodes)
-No chlorophyll development
-“Shoot” bent at tip (hook)
How does exposure to ethylene modify the development of an etiolated dicot seedling?
-reduced stem elongation, lateral swelling, horizontal growth (roots grow sideways)
Triple response
How does ethylene effect the elongation of leaf petioles in water lily or stem elongation in deep-water rice?
Water lily and “deep water” rice may undergo stem or petiole elongation under water. Ethylene production is reduced but so is diffusion out of the shoot which produces a net increase in ethylene concentration and increased elongation rates.
Based on your knowledge of ethylene and auxin, offer an explanation as to why the lamps might be the cause of leaf drop.
a. Leaf maintenance produce low auxin which go to petiole and inhibit ethylene production.
b. Shedding induction phase- small auxin is blocked and ethylene is produced in high concentration and cause layers of cells to break down
c. Shedding phase seperation layer digested

ethylene Active ingredient in coal gas and pollutants; produces “triple response”.
What is ethephon and how is it a useful compound for commercial modifications of plants?
is sprayed on plant and it begins to break down and release ethylene
What are some plant responses that are modified commercially? How is inhibition of ethylene production important commercially?
fruit storage (low o2 inhibits oxidase, cool temperature inhibits resp., high co2); cut flowers (Ag)- inhibitor of ethylene process by inhibiting ACC synthase
How was dormin discovered and how is it related to abscisic acid (ABA)? How many carbons does ABA possess?
promotion of bud dormancy in sycamore- dormin. Abscisin II= dormin= ABA
What is a precursor for ABA synthesis by higher plants? How is ABA detected in plant tissues?
Derived from terpenoid precursor
Bioassays – inhibition of coleoptile growth, stomatal closure

GC or HPLC – requires several purification steps (TLC)
How is abscisic acid (ABA) synthesized in plants? How is ABA concentration regulated in plant tissues?
IPP-->aba aldehyde-->aba
How is ABA thought to be related to seed development?
ABA promotes:

Accumulation of seed storage protein

Desiccation tolerance in the embryo
What are three environmental factors that can release seeds from embryo dormancy? What is thought to be the role of ABA in embryo dormancy?
Afterripening (reduced moisture content); Chilling (0-10°C for imbibed seeds); Light (exposure or photoperiod requirement)

ABA promotes:

Accumulation of seed storage protein


Desiccation tolerance in the embryo

Release from embryo dormancy
How does ABA concentration appear to be related to bud dormancy in woody plants and GA-induced synthesis of hydrolases in grain seeds?
Accumulates in dormant buds (woody species)

Protection of meristems of woody plants in cold environments

May involve interactions with other hormones
How does ABA concentration change with water stress in whole plants and how does this relate to stomatal opening and root and shoot growth?
Closes stomata in response to water stress

Commelina communis epidermal strips - without and with 10 micromolar ABA, 10-30 minutes

Stomatal resistance and plant water stress
How does ABA concentration relate to abscission and leaf senescence?
?
In general where is ABA synthesized in plants? Where are auxins, gibberellins, cytokinins, and ethylene synthesized in plants?
look at lec 25
In general where is ABA synthesized in plants? Where are auxins, gibberellins, cytokinins, and ethylene synthesized in plants?
look at lec 25
In general where is ABA synthesized in plants? Where are auxins, gibberellins, cytokinins, and ethylene synthesized in plants?
look at lec 25
What are the four "nouveau" hormones? What is the general function of each of these hormones?
Systemin - long-distance signal produced in response to herbivore attack

b. Jasmonic acid - signal that activates cellular responses to herbivore (pathogen) attack

c. Salicylic acid - long-distance signal that triggers systemic acquired resistance (SAR) to pathogens

d. Brassinolide - regulates a variety of cellular growth and development properties
What are the four "nouveau" hormones? What is the general function of each of these hormones?
Systemin - long-distance signal produced in response to herbivore attack

b. Jasmonic acid - signal that activates cellular responses to herbivore (pathogen) attack

c. Salicylic acid - long-distance signal that triggers systemic acquired resistance (SAR) to pathogens

d. Brassinolide - regulates a variety of cellular growth and development properties
What are the four "nouveau" hormones? What is the general function of each of these hormones?
Systemin - long-distance signal produced in response to herbivore attack

b. Jasmonic acid - signal that activates cellular responses to herbivore (pathogen) attack

c. Salicylic acid - long-distance signal that triggers systemic acquired resistance (SAR) to pathogens

d. Brassinolide - regulates a variety of cellular growth and development properties
How are the two forms of phytochrome named and what are the approximate wavelengths for maximum absorption for each?
red stimulates, far-red light inhibits seed germination R/FR= fluence rate 660nm/ fluence rate 730 nm
How are the two forms of phytochrome named and what are the approximate wavelengths for maximum absorption for each?
red stimulates, far-red light inhibits seed germination R/FR= fluence rate 660nm/ fluence rate 730 nm
How are the two forms of phytochrome named and what are the approximate wavelengths for maximum absorption for each?
red stimulates, far-red light inhibits seed germination R/FR= fluence rate 660nm/ fluence rate 730 nm
What happens to a phytochrome molecule when it absorbs light at its maximum wavelength?
converted back?
What happens to a phytochrome molecule when it absorbs light at its maximum wavelength?
converted back?
What form of phytochrome is synthesized in plants and how is the amount of phytochrome naturally maintained in plants?
?
What form of phytochrome is synthesized in plants and how is the amount of phytochrome naturally maintained in plants?
?
Imbibed seeds exposed to red light (approximately 665 nm) and placed in the dark germinate while imbibed seeds exposed to far-red light (approximately 730 nm) and placed in the dark do not. How are these responses thought to be related to the relative amounts of the different forms of phytochrome in plants?
May be biochemical or morphological

2. Vary in lag time (time between stimulation and observed response)

3. Vary in escape from photoreversibility

4. Distinguished by light requirement
Imbibed seeds exposed to red light (approximately 665 nm) and placed in the dark germinate while imbibed seeds exposed to far-red light (approximately 730 nm) and placed in the dark do not. How are these responses thought to be related to the relative amounts of the different forms of phytochrome in plants?
May be biochemical or morphological

2. Vary in lag time (time between stimulation and observed response)

3. Vary in escape from photoreversibility

4. Distinguished by light requirement
What happens to a phytochrome molecule when it absorbs light at its maximum wavelength?
converted back?
Certain seeds germinate in open areas but remain dormant under heavy leaf canopies. What is the ecological advantage to the plant seed of being able to detect these different environments?
Sun and shade morphology in “sun” plants (Fig. 17.11)

Low Pfr/Ptotal (low R/Fr) promotes stem elongation, broader leaves

2. Regulation of germination in small seeds

Low Pfr/Ptotal (low R/Fr) can inhibit germination
Certain seeds germinate in open areas but remain dormant under heavy leaf canopies. What is the ecological advantage to the plant seed of being able to detect these different environments?
Sun and shade morphology in “sun” plants (Fig. 17.11)

Low Pfr/Ptotal (low R/Fr) promotes stem elongation, broader leaves

2. Regulation of germination in small seeds

Low Pfr/Ptotal (low R/Fr) can inhibit germination
What form of phytochrome is synthesized in plants and how is the amount of phytochrome naturally maintained in plants?
?
Define the term circadian rhythm. What is nyctinastic movement of leaves?
Circadian rhythms-cycles in physiology or movement that take about a day
-cycle is precisely maintained byplants “erception” of photoperiod length
-ex:nysicastic movement of leaves
Define the term circadian rhythm. What is nyctinastic movement of leaves?
Circadian rhythms-cycles in physiology or movement that take about a day
-cycle is precisely maintained byplants “erception” of photoperiod length
-ex:nysicastic movement of leaves
Imbibed seeds exposed to red light (approximately 665 nm) and placed in the dark germinate while imbibed seeds exposed to far-red light (approximately 730 nm) and placed in the dark do not. How are these responses thought to be related to the relative amounts of the different forms of phytochrome in plants?
May be biochemical or morphological

2. Vary in lag time (time between stimulation and observed response)

3. Vary in escape from photoreversibility

4. Distinguished by light requirement
Nyctinastic movement follows a circadian cycle in some leguminous plants. What is thought to be the role of phytochrome in this movement?
Mimosa pudica – sensitive plant – circadian cycle in leaf angle (nyctinastic movement), see Fig. 17.12, Fig. 17.13
Certain seeds germinate in open areas but remain dormant under heavy leaf canopies. What is the ecological advantage to the plant seed of being able to detect these different environments?
Sun and shade morphology in “sun” plants (Fig. 17.11)

Low Pfr/Ptotal (low R/Fr) promotes stem elongation, broader leaves

2. Regulation of germination in small seeds

Low Pfr/Ptotal (low R/Fr) can inhibit germination
What are the four possible types of tissues produced by a floral meristem?
sepals, petals, carpels, and stamens
Nyctinastic movement follows a circadian cycle in some leguminous plants. What is thought to be the role of phytochrome in this movement?
Mimosa pudica – sensitive plant – circadian cycle in leaf angle (nyctinastic movement), see Fig. 17.12, Fig. 17.13
What was the “Maryland Mammoth”, how did it get its name, and how did it help in our understanding of photoperiod control of flowering?
maryland mammoth mutant failed to flower in the summer
-in the greenhouse Maryland mammoth flowered in December and was used as control
-experiments showed mammoth responded to the length of the dark period not light
What are the four possible types of tissues produced by a floral meristem?
sepals, petals, carpels, and stamens
Define the term circadian rhythm. What is nyctinastic movement of leaves?
Circadian rhythms-cycles in physiology or movement that take about a day
-cycle is precisely maintained byplants “erception” of photoperiod length
-ex:nysicastic movement of leaves
What was the “Maryland Mammoth”, how did it get its name, and how did it help in our understanding of photoperiod control of flowering?
maryland mammoth mutant failed to flower in the summer
-in the greenhouse Maryland mammoth flowered in December and was used as control
-experiments showed mammoth responded to the length of the dark period not light
Nyctinastic movement follows a circadian cycle in some leguminous plants. What is thought to be the role of phytochrome in this movement?
Mimosa pudica – sensitive plant – circadian cycle in leaf angle (nyctinastic movement), see Fig. 17.12, Fig. 17.13
Cocklebur plants are vegetative in summer but flower in the fall. Describe a mechanism that would explain this control of floral initiation in terms of phytochrome.
pytochrome model
during day more pr  high pfr during dark pfr converts slowly back to pr so pfr pool size gets smaller during night. Flower initation depends on pfr at dawn. Below min cues long-night plant. Above min cues short night plant. Short circuit slow conversion by adding far red and interrupt degredation of pfr
What are the four possible types of tissues produced by a floral meristem?
sepals, petals, carpels, and stamens
Many species from the genus Fuschia are the opposite from cocklebur in that in early spring when days are short they do not flower but in April or May they begin to flower. How could floral initiation in Fuschia sp be related to phytochrome?
1. Pfr is at max at dusk
2. conversion to pr measures length of dark period
3. circadian clock times “reading” of the size of the pfr pool at dawn
4. long night (sd) plants flower when pfr pool is below critical value (at dawn)
5. short night (ld) plants flower when pfr pool dies not fall below critical value
What was the “Maryland Mammoth”, how did it get its name, and how did it help in our understanding of photoperiod control of flowering?
maryland mammoth mutant failed to flower in the summer
-in the greenhouse Maryland mammoth flowered in December and was used as control
-experiments showed mammoth responded to the length of the dark period not light
Cocklebur plants are vegetative in summer but flower in the fall. Describe a mechanism that would explain this control of floral initiation in terms of phytochrome.
pytochrome model
during day more pr  high pfr during dark pfr converts slowly back to pr so pfr pool size gets smaller during night. Flower initation depends on pfr at dawn. Below min cues long-night plant. Above min cues short night plant. Short circuit slow conversion by adding far red and interrupt degredation of pfr
Cocklebur plants are vegetative in summer but flower in the fall. Describe a mechanism that would explain this control of floral initiation in terms of phytochrome.
pytochrome model
during day more pr  high pfr during dark pfr converts slowly back to pr so pfr pool size gets smaller during night. Flower initation depends on pfr at dawn. Below min cues long-night plant. Above min cues short night plant. Short circuit slow conversion by adding far red and interrupt degredation of pfr
Many species from the genus Fuschia are the opposite from cocklebur in that in early spring when days are short they do not flower but in April or May they begin to flower. How could floral initiation in Fuschia sp be related to phytochrome?
1. Pfr is at max at dusk
2. conversion to pr measures length of dark period
3. circadian clock times “reading” of the size of the pfr pool at dawn
4. long night (sd) plants flower when pfr pool is below critical value (at dawn)
5. short night (ld) plants flower when pfr pool dies not fall below critical value
Many species from the genus Fuschia are the opposite from cocklebur in that in early spring when days are short they do not flower but in April or May they begin to flower. How could floral initiation in Fuschia sp be related to phytochrome?
1. Pfr is at max at dusk
2. conversion to pr measures length of dark period
3. circadian clock times “reading” of the size of the pfr pool at dawn
4. long night (sd) plants flower when pfr pool is below critical value (at dawn)
5. short night (ld) plants flower when pfr pool dies not fall below critical value