15 - Plant signalling Flashcards
Signal Transduction causes two responses, what are they?
- Pi’n cascade
- 2nd messanger
In response to a signal being transduced into the plant, what are the potential next steps in signal transduction?
- activate/deactivate genes
- increase or decrease protein activity - translation
- Increase or decrease Ion flow - channel or pump
list some of the potential signals
- light
- gravity
- chemical
- hormones
- touch
Where the stimulus of a signal is elicited, is this also where the response will happen?
No
In plants what is the typical 2nd messanger?
Ca2+
Which hormone supports the growth in the main stem yet ensure lateral buts remain dormant?
auxin
What is the effect of a high concentration of auxin on a plant?
hight concentration will bring water, causing cells to elongate and growth - therefore bending
Describe whats going on with phtotropism
growth towards the light “light turning”
[] increases on darker side of plant causing elongation of cells
what is the protein that have been found that make cell walls extensibe by interfering with the ionic bonds b/t cellulose microfibrils - causing cell walls to loosen and new cellulose nmicrofibrils produced to extend the cells length
expansins
What are the two things that must happed for a plant to get larger?
- cell wall must expand - expansins
- increase in volument and turgor pressure - increase [K+] therefore increase H2O
Describe the steps to the acid-growth hypothesis for cell elongation
What activated proton pumps lower the pH outside the cell membrane in response to auxin, a series of events leads to
- and intake of water
- expansion of the cell wall
Result: expansion of cell wall
What is the root of the workd gravitropism
“gravity-turning”
Where are the cells found that are responsible for responding to gravity
root cap
What is the statolith hypothesis?
that dense starch-storing organelles called amyloplasts fxn as gravity receptors
How do the amyloplasts support the statolith hypothesis
gravity pulls the heavy amyloplasts to the bottom of the cells, activiating sensory protein that initates the gravitropic response
What are the amyloplasts filled with making them dense and therefore more heavy
starch
what is the hormone responsible for phototropism and gravitropism
auxin
What is up with 2-4-D
herbicide - uncontrolled growth of dicots
doesnt kill lawns
kills broad leaves - monocots
What is the root term of cytokinins
cell division
what do cytokinins do?
causes cell division
What is the role of cytokinins
- lateral bud growth
- delay in aging
What is the role of the hormone gibberellins?
- growth stimulation
- stem growth and elogation
- flower stimulation
- seed germination
__________ stimulates growth and ___________ inhibits it
Gibberellins
Abscisic acid or ABA
what does gibberellins do to starch?
converts to sugar
What does ABA do ?
- Inhibits bud growth & seed germination
- closes stomata when H2O stressed
__________ is the regulation process of aging, decline, and eventual death of an entire organism or particular organs such as plant fruits and leaves
Senescence
What is the hormone most strongly associated with senscence?
ethylene
What are the three aspects of senescence that ethylene contibutes to
- fruit ripening
- fading of flowers
- abscission - detachment of leaves
define abscission
detachment of leaves
What do fruit growers manuipulate in order to control fruit ripening?
ethylene
___________ and __________ are thought to have opposite effects on some of the processes involved in senscence
ethylene and cytokinins
___________ can define the long axis of the body
auxin
__________ promote cell growth
gibberellins
__________ promote cell division
cytokinins
___________ slows or prevents growth
ABA
_______________ signals senescence
ethylene
Describe how stomata close in response to ABA
ABA binds to receptors on guard cells
- pumping by H+ ATPases stops. Outward-directioed Cl- exits along electrochemical gradient
- change in Mb potential opens outward directed K+ channels. K+ exits along electrochemical gradient
- H2O follows by osmosis
- Cell shrinks
What is tropism
directed response to a stimulus
name the different types of tropisms
- thigmotropism - bending to touch - ie tendrils
- thigmomorphogensesis - stems grow shorter or thicker - ie alpine trees due to wind
- Gravitropism
- phototropism
- hydrotropism
What does nastic movement mean
no directional movement
What kind of movement do guard cells do?
nastic movements - turgor
what is seismonasty movement?
movement in response to physical touch
ie- closing up if a bug comes to eat them
what is nyctinasity movement?
response to light
All of the following statements about plant hormones are correct EXCEPT for:
Select one:
a. They can trigger a phosphorylation cascade
b. They can exist in a gaseous form
c. They trigger a response by binding to a receptor.
d. They exert their effects only in the same cells that produce them.
e. They can increase the amount of protein in a cell
They exert their effects only in the same cells that produce them.
The plant response to wind is called
Select one:
A. Seismonasty
B. Phototropism
C. Nyctinasty
D. Apical dominance
E. Thigmomorphogenesis
Thigmomorphogenesis
The hormone that helps plants respond to drought is
Select one:
A. Gibberellin
B. Cytokinin
C. Ethylene
D. Abscisic acid
E. Auxin
Abscisic acid
If you pinched your plant back to make it bushier you would be pinching off
Select one:
A. Cytokinin
B. Abscisic acid
C. Ethylene
D. Gibberellin
E. Auxin
Auxin
The gibberellins
Select one:
A. Are gases at room termperature
B. Are produced only by fungi
C. Are responsible for phototropism and gravitropism
D. Cause flowering in plants
E. Inhibit the synthesis of digestive enzymes by barley seeds
Cause flowering in plants
Fruit bowls and hanging baskets often have open wires. What is the advantage of these open spaces?
Select one:
A. Prevents gibberellins from causing the formation of flowers on the fruit
B. Allows oxygen in the air to stimulate the production of abscisic acid to hasten the ripening of fruit
C. Allows sunlight to penetrate through the openings to stimulate fruit ripening
D. Allows the evaporation of ethylene, thus slowing ripening of the fruit
E. Allows carbon dioxide in the air to stimulate cytokinin production to stimulate fruit ripening
Allows the evaporation of ethylene, thus slowing ripening of the fruit
