Light as an Environmental Signal Flashcards
What levels of irradiance is there high and low in the canopy?
High: high irradiance
Low: low irradiance
What is irradiation?
The amount of light on a surface per area per second.
What light penetrates the furthest into the canopy?
Far red light
How can plants tell what their current and future competition is?
Current: R:FR ratio from top
Future: R:FR ratio from side
What is photomorphogenesis?
The origin of the form of a plant in response to light
What is phytochrome?
A photoreceptor
Measures light quality by sensing red and far-red light (LFR)
Measures light quantity by measuring photons (VLFR)
What are the phytochrome mediated responses?
- LFR: low fluence response
- VLFR: very low fluence response
- HIR: high irradiance response
What two forms can phytochrome exist in?
Pr: inactive
Pfr: active
What activates Pfr?
Red light activates, far-red inactivates
What does the proportion of Pr to Pfr depend on?
R:FR ratio
What percentage of phytochrome is Pr and Pfr in 600nm?
Pr: 20%
Pfr: 80%
What percentage of phytochrome is Pr and Pfr in 730nm?
Pr: 97%
Pfr: 3%
What is a LFR (low fluence response)
Senses light quality
Promoted seed germination
Stimulated by red light. Inhibited by far-red
Can be far-red reversed.
What is a VLFR (very low fluence response)
Acts as a photon detector
Can be triggered by red or far-red light
Not far-red reversable
What is a HIR (high irradiance response)
Detects irradiance
Can be triggered by red or far-red light
Not far-red reversable
Activation of Pfr requires an intermediate state, in high irradiance, more phytochrome is in intermediate state which triggers HIR.
