Ro 2 Flashcards
plants sense and respond to light using ____, a specialized ____ protein.
phytochrome, light-sensing
Plants exhibit different growth patterns depending on light conditions
In Darkness:
____
Cotyledons ____
In Light:
____
____.
Initiation of pigment synthesis (e.g., chlorophyll and carotenoids).
elongated cotyledons
folded, closed, unexpanded
shortened cotyledon
straight apical hook
photosynthesis, pigments, etc
Plants respond to specific parts of the light spectrum:
Blue light: ____ nm.
Red light: ____ nm.
Far-red light: ____ nm.
400 - 500 nm
650 - 680 nm
710–740 nm
Green leaves filter light, reducing ____ light and increasing ____ light beneath the canopy.
red, far-red
Two Hypotheses for light sensing:
Plants have separate sensors for red and far-red light, working ____.
A single ____ molecule changes between two forms in response to red or far-red light.
antagonistically, photo-reversible
Scientists purified a ____ pigment protein (~125 kDa) and named it ____.
The ____ hypothesis was correct: (first or second)
Pr (red-light absorbing form) is converted to Pfr (far-red-light absorbing form) by ____ light.
Far-red light converts ____ back to ____.
blue, phytochrome, second
red,
Pfr, Pr
Light does not fully convert phytochrome into one form. What does this mean?
Red light: 88% Pfr, 12% Pr.
Far-red light: 2% Pfr, 98% Pr.
what is the physiologically active form, pr or pfr
pfr
what does pfr vs pr absorb
pfr - green
pr - red
The balance of red and far-red light allows plants to detect shade (far-red enriched light) and adjust growth (e.g., elongation to escape shade).
high R:fr means
high fr:r means
high red:far red - no shade avoidance response
high far red: red - growth and elongation
Role of Phytochromes in Signaling:
In the nucleus, phytochromes can: do 3 things
____ other proteins.
Be ____ by other proteins.
____ proteins to regulate signaling.
phosphorylate, phosphorylated, degrade
