Plant Responses to the Environment - Light Flashcards
what triggers plant stress responses (list some) (6)
environmental variability:
- light intensity/spectral quality
- water potential/nutrients
- temperature
- day-length
- herbivores/pathogens
- distinguishing up from down
what triggers plant stress responses (list some) (6)
environmental variability:
- light intensity/spectral quality
- water potential/nutrients
- temperature
- day-length
- herbivores/pathogens
- distinguishing up from down
PAR
- photosynthesis active radiation
plant responses: daily variability (2)
- sense PAR daily cycles (day/night) and day to day variability
- responds by regulating relatively SIMPLE physiological processes, such as stomatal opening
plant responses: seasonal variability
- plant senses difference in the average PAR between seasons
- plants responds by regulating COMPLEX developmental programs, such as seed germination, flowering, fruit development, senescence, etc
what are some environmental variations that plants detect when responding to daily and seasonal variability (4)
- light/PAR
- temperature
- rainfall
- nutrients
sensing mechanisms at the cellular level: plants vs animals (2)
- have similar sensing mechanisms/fundamental components at the cellular level
- main difference is the stimulus that triggers the physiological/cellular response
what is the general response to this stimulus: gravity
- cells on opposite side of root or shoot elongate; tissue curves
what is the general response to this stimulus: touch/wind
- stems grow shorter and thicker
what is the general response to this stimulus: touch (venus fly trap)
- target cells swell and trap shuts
what is the general response to this stimulus: pathogens
- hypersensitive response where infected cells die
what is the general response to this stimulus: herbivores
- insecticide production
relationship between: stomatal opening, transpiration, and light intensity (3)
- increase in light intensity:
- stomatal openings increase
- plant transpiration, how much water is lost through the stomata, increases
how do plants respond to blue/red light (2)
- activates photosynthetic antenna and induces ATP and NADPH synthesis
- facilitates CO2 capture by promoting stomatal opening
which light beams are best at promoting stomatal opening (3)
- only red light is the weakest
- only blue light is intermediate
- both red and blue light is the strongest
blue light receptors (2)
- sensed by phototropins PHOT1 and PHOT2 receptors, which are protein kinases
- PHOT1/PHOT2 are activated by interactions with a chromophore (a light absorbing molecule)
how does the blue light signalling pathway trigger stomatal opening: absence of blue light (2)
- PHOT1 domains bind non-covalently (weakly) to the FMN chromophore
- no autophosphorylation, no signal amplification, stoma closed
how does the blue light signalling pathway trigger stomatal opening: presence of blue light
- PHOT1 domains bind covalently (strongly) to the FMN chromophore
- autophosphorylation, signal amplification, stoma open
what results from the auto-phosphorylation of PHOT1/2
- the photoreceptors change their activity and activate signal transduction
is K+ essential for plants (2)
- K+ is an essential osmotic regulator in stomata
- is a common additive in fertilizers as it is often a limiting factor in soils
where do seeds “prefer” to germinate
- in the sun: high C fixation, so seedling is well-fed
where do seeds not “prefer” to germinate (2)
- in the shade: low C fixation, so seedling is starving
- seed will still germinate with water, but this is not preferred as there is limited production of biomass
sunlight spectrum light richness (2)
- sunlight is rich in red light and poor in far red light
- in the sun, plants will receive more red photons than far red photons
how would you describe the effects of red and far red light on germination
- antagonistic effects on germination
how can plants sense shade (3)
- far red light is poorly absorbed by chlorophyll a
- red light is strongly absorbed by chlorophyll a
- as a results, seeds can sense the FR:R ratio they receive through a single phytochrome receptor
what kind of FR:R ratio will shade have and its results
- high FR:R ratio
- dormancy of seeds; low germination
what kind of FR:R ratio will sun have and its results
- low ratio of FR:R light
- metabolism activation in the seeds; germination
phytochrome (2)
- a single receptor that moves between two conformations, depending on the predominant light wavelength (FR or R)
- changes between conformations VERY FAST
phytochrome conformations (2)
- changes to Pfr after absorbing red light
- changes to Pr after absorbing far red light
what is the active form of the phytochrome
- Pfr is the active form that will trigger germination
if there are consecutive flashes of different wavelengths (FR vs R), which will determine seed germination
- the wavelength of the last flash will determine seed germination
how are SHADE and the NIGHT different (2)
- shade: presence of red and far red photons; fast phytochrome response
- night: absence of red and far red photons; slow phytochrome response
