Plant Control Systems Flashcards
1
Q
Unlike animals which respond by movement, plants respond to stimuli by
A
altering growth and development.
2
Q
response in plants is carried out via
A
signal transduction
3
Q
what’s etiolation
A
the morphological adaptation required for growing in the dark.
4
Q
what happens when a plant that has been growing in the dark reaches light?
A
de-etiolation (greening) commences.
-roots lengthen, leaves expand, shoot begins to produce chlorophyll to start photosynthesis.
5
Q
describe reception in signal transduction in plants (de-etiolation ex)
A
- light signal is detected by a phytochrome receptor located in the cytoplasm.
- this activates at least 2 signal transduction pathways.
6
Q
describe the two transduction pathways in signal transduction in plants (de-etiolation ex)
A
- first pathway: cGMP
-weak levels of light trigger the phytochrome and initiate the secondary messenger cGMP, through activation of the enzyme guanylyl cyclase.
-cGMP then activates protein kinases, which carries the signal into a response. - second pathway Ca2+ ions
-phytochrome activation opens up Ca2+ channels, flooding the cytosol with increased Ca2+.
-this activates another protein kinase to initiate a response.
7
Q
describe the response in signal transduction in plants (de-etiolation ex)
A
- both pathways lead to expression of genes for proteins that help de-etiolation occur.
- post-transcriptional modification for proteins.
-proteins are phosphorlyated, altering protein shape and function. -protein phosphotases dephosphorylate enzymes, turning off signals. - transcriptional regulation
-transcription factors bind to specific regions of DNA to control transcription of genes on DNA.
-activators =incr. transcription
-repressors =decr.
8
Q
what happens if only one of the transduction pathways in de-etiolation are activated
A
then there will be no de-etiolation (greening)
9
Q
what are products of response in plant signal transduction
A
enzymes for photosynthesis, chlorophyll production, plant hormone levels.
10
Q
how are hormones transported in plants
A
in the phloem sap
11
Q
what’s phototropism and tropism
A
phototropism- plants generally grow towards light
tropism- plant organs curving toward or away from a stimulus.
12
Q
where are auxins produced and function
A
- produced mostly in shoot tips in shoot apical meristems and young leaves
- functions: controls spatial organisation of the plant, affects size, shape, environment of branches and stems. Promotes stem elongation.
13
Q
where are cytokinins produced and function.
A
- produced in actively growing tissues, primarily in roots, embryos, fruits
- functions: works with auxins to promote cell divison and differentiation. -if just auxin is present cells will grow but not divide. if just cytokinins, no effect.
- causes apical dominance -apical bud surpresses growth of axillary buds.
- anti-aging-slows apoptosis, stops protein breakdown, and stimulates RNA and protein production.
14
Q
where are gibberellins produced and function.
A
- produced in young roots and leaves
- function: stem elongation- stimulating both cell division and elongation - work with auxins, fruit growth- need both auxins and gibberellins for fruit to develop, and germination-signals seed to break dormancy, stimulates digestive enzymes for endosperm breakdown.
15
Q
where is abscisic acid (ABA) found and function
A
- found everywhere in plant
- function: slows growth, causes seeds to remain dormant (prevents germination when environment not good). so when ABA decreases, seed will germinate.
-ABA also closes stomata to prevent water loss.
16
Q
ratio of what two hormones determines whether the seed is dormant or will germinate
A
abscisic acid and gibberellins
17
Q
when is ethylene hormone produced, what does it do?
A
- produced in response to mechanical stresses like drought, flooding, mechanical pressure, injury, and infection.
- also produced during fruit ripening, apoptosis, and leaf abscission (leaves falling in fall).
- for mechanical stress it causes a triple response: shoots avoid obstacles via horizontal growth.
-stem elongation, thickening of the stem, and curvature of the stem
18
Q
how does ethylene initiate senescence (leaf/flower shedding)
A
burst of ethylene initiates the cascade of apoptosis
19
Q
aging leaves will have more or less auxin and ethylene
A
less auxin, more ethylene
20
Q
how does ethylene cause fruit ripening
A
- when ready, burst of ethylene triggers enzymatic breakdown of cell walls allowing the fruit to soften, and convert starch to sugar to make it sweeter.
- chain reaction: ethylene promotes ripening, and ripening produces more ethylene.
21
Q
A
22
Q
commercial producers will store fruit in _ to slow the production of ethylene or ___ to promote ripening
A
store fruit in CO2 to slow ethylene production.
spray with ethylene to promote ripening.
23
Q
what are brassinosteroids? what do they do?
A
- steroids, and cholesterol
- induce cell elongation and division in stems, slow down leaf abscission, and promote xylem differentiation.
24
Q
what are jasmonates? what do they do?
A
- fatty-acid derived molecules
- function: plant defence and development
- Also, key roles in nectar secretion, fruit
ripening, pollen production, flowering
time, root growth, seed germination,
tuber formation, promoting
mycorrhizal associations, tendril
coiling
25
what are strigolactones? what do they do?
* xylem-mobile chemicals
* stimulate seed germination, surpress adventitious root development, helps with mycorrhizae, and controls apical dominance.
26
photomorphogenesis
the effect of light on plant growth and development
-allows plants to measure day length, time of year, seasons.
27
what are the two main photoreceptors and what do they do
* blue-light photoreceptors-have a role in phototropism, light-induced stomata opening, light-induced hypocotyl growth reduction after breaking ground.
* phytochromes -red and far red have reversible, opposite effects.
-red light=germination, far red=inhibits germination
28
there are several kinds of phytochromes
Pr absorbs _ light and is converted to _
Pfr absorbs _ and is converted back to _
Pr absorbs red light and is converted to Pfr
Pfr absorbs far red and converted back to Pr
29
higher or lower ratio of Pfr:Pr initiates germination?
higher ratio
30
during _ the conversion between phytochrome states (Pr and Pfr) reach equilibrium
during the day
31
if plant is shaded, phytochrome ratio of Pr is higher or lower
higher
32
what are circadian rhythms
responses occuring on a 24 hr cycle, without a known underlying cause
33
what are circadian rhythms controlled by
gene transcription
34
state the length of the photoperiod that induces flowering for the following (short or long)
* short day plants
* long day plants
* day neutral plants
* short day > shorter photoperiod
* long day > longer
* day neutral > flower when a certain stage of maturity is reached rather than day length
35
is flowering controlled by day or night length
night length, they need a required amount of continous dark to flower.
36
whats gravitropism
do roots vs shoots display positive or negative gravitropism
allows the plant to grow towards the light, regardless of position
roots-positive (grow down)
shoots-negative (against gravity)
37
statoliths
starch containing plastids in plant tissues that settle due to gravity.
-in roots near root cap
38
thigomorphogenesis
refers to changes in morphology due to physical/mechanical disturbances.
39
thigmotropism
directional growth due to touch
40
how do plants respond to Flooding
* too much water suffocates plant roots
* oxygen deprivation stimulates ethylene, which initiates apoptosis to kill off cells in the roots to make their own spaces.
41
how do plants respond to drought
* close of their stomata during the day, in response to lack of water, due to production of ABA.
-some species shed their leaves
42
plant response salt stress
* Excess salt lowers the water potential in the soil, resulting in less water uptake by the plant
* Can overcome this by producing their own solutes so they don’t acquire the toxic ones
(but only short term)
* Halophytes can pump out excess salt from the leaf epidermis
43
plant response to heat stress
Excessive heat can denature plant proteins, disrupting metabolism
* Transpiration can cool leaves, until water loss becomes overwhelming
* Most plants can produce heat-shock proteins at temps >40C which help prevent protein
denaturation in the plant body
* These are chaperone proteins that help proteins fold properly in excess heat
44
whats the plants response to cold stress
Cooler temperatures change the plasma membrane fluidity since lipids become locked into
crystalline structures
* Alters solute transport across membranes and protein function
* Plants can alter lipid composition in their membranes -> increase unsaturated fatty acids
* But it can take days to adjust so really fast cold snaps are still a problem
45
what are plants defences against pathogens.
1. epidermis, w waxy cuticle, and periderm. However pathogens can still sneak through stomata.
2. chemicals- plants produce chemicals that are toxic to invaders or inhibit their growth within the plant.
3. immunity via PAMP-triggered immunity and effector-triggered immunity.
## Footnote
(PAMP=PATHOGEN-ASSOCIATED MOLECULAR PATTERNS)
46
PAMP recognition triggers what
-signal transduction pathways to produce a response.
47
the plant immune system is made up of hundreds of
disease resisting genes, each gene codes for a protein that is activated in the presence of the effector. signal trasduction then initiates lots of responses.
48
what are the 2 responses that disease resisting genes cause
1. Hypersenstive response- programmed cell death at infection site. increased production of lignin and cell wall cross linkages. -Production of enzymes and chemicals (jasmonates) that impair the pathogen’s cell wall integrity, metabolism, or reproduction
2. Systemic acquired resistance -send signals to rest of plant, Methylsalicylic acid is produced at the infection site, carried by phloem, and converted to salicylic acid
which promote signal transduction and the production of more defence further in the plant
49
how does herbivory affect the plant
it causes mechanical stress on plant
* reducing plant size
* reducing photosynthesis capacity
* restricts growth, plants divert energy to anti herivory defence
* it opens sites for infection by pathogens.
50
what defences have plants adapt against herbivory
* physical defences: thorns, trichomes
* chemical defenses: terrible taste, toxic, hallucinogenic effects
* combination of both burning sap, irritants
