12 Flashcards
Light induces fast/slow transitions (High Pfr:Pr ratio)?
Fast
Night induces fast/slow reversion (Low Pfr:Pr ratio)?
Slow
How to plants sense the ratio of the Pfr:Pr ratio?
Short night plants need a relatively high/low Pfr:Pr ratio at sunrise?
High
Long night plants need a very high/low Pfr:Pr ratio at sunrise?
Low
Primary compound?
Essential for growth
Secondary compound?
Not essential but does benefit the plant.
Auxin roles? 4•
•wound response
•flowering
•fruit growth and development
•ethylene biosynthesis
Auxin at high concentrations are powerful?
Herbicides.
Herbicides?
Plant killers
!!!!!!!Auxin is responsible for?
•Cell elongation
•Gravitational pull
Once PHOT1 is phosphorylated, then?
A phototropic response is initiated.
Where in the plant is the blue light sensed?
By coleoptile tip.
Where is the response of the bend of the plant occurring?
In the lower coleoptile
How does the lower coleoptile bend if the tip senses?
There is chemical diffusion that transports through the plant
When light hits the plant, how does that induce bending?
Auxin gets hit by the light, and goes into the dark side of the plant. There is a higher concentration in that side, and diffuses down. There is still a higher concentration down the plant. Since auxin causes cell elongation, it facilitates cell elongation on the shaded side.
Acid growth hypothesis?
Plants are able to loosen their cell wall by raising its pH by auxin binding to an ABP1 receptor, which facilitates H+/ATPase proton pump. Protons will pump outside of the cell. Potassium will facilitate diffuse inside of the cell. This decreases solute potential, which decreases water potential, and water will diffuse into the cell. This increases turgor pressure.
Expansion?
Proton pumping also ends to loosening of cellulose micro-fibrils in cell wall by activating expansion. It break bonds between cellulose microfibris. It weakens the cell wall. It is a signal for cell wall synthesis (button example)
!!!!!!When does expansin get activated?
When the cell wall gets acidified
Gravitropism?
•Roots will grow towards gravity, and shoots grow against gravity. •Roots have a tip with sensors called the columella cells. •Amyloplasts are pulled towards a specific side in the cell by gravity. •Auxin are evenly distributed when roots are growing downwards. •When amyloplasts are not distributed evenly, then auxin will flow towards amyloplasts, and there will be a difference of concentration, auxin-induced asymmetric growth. This will INHIBIT cell elongation at the side with most amyloplasts since there are WAY TOO MANY auxin. The other side grows normally.
