Ch. 39 Plant Responses Flashcards
big ideas: tropisms (photo/gravi/thigmo), auxin, acid growth hypothesis, Pr and Pfr, signal transduction pathway
what is etiolation?
the responses of a plant to growing in darkness
what is de-etioliation?
the series of changes a plant previously in dark undergoes when being exposed to the sun
what are the 3 steps of cell signal transduction?
-reception, transduction, and response
what are the steps of the 2nd messenger cGMP cascade?
- cGMP activates protein kinases / PKs
- PKs activate transcription factors (TFs)
- TFs turn on genes for transcription
- transcribed genes get turned into response proteins
what is the 1st step of a plant cell’s signal transduction pathway?
1st step begins when a stimulus (ex - light) binds to a receptor, such as phytochrome
what is phototropism?
growth of a plant in response to light. can be towards (+) or away from (-)
what is the major function of auxin?
responsible for tropism of plants - phototropism and gravitropism
how does auxin result in phototropism?
auxin moves to the opposite side of the light source of the plant, causing elongation in the opposite side which results in the plant “bending” towards the source
how is auxin transported? [what is polar transport]?
auxin moves unidirectionally: always from shoot tip downwards, and is transported through cells via diffusion by active transport
what does auxin stimulate cells to do?
auxin stimulates shady cells to pump H+ out of the cell into the cell wall
what is the acid growth hypothesis?
a hypothesis that auxins causing cells to pump H+ out of the cell, and therefore activating enzymes such as expansin, results in enlargement of the cell
what does auxin do to the inside of a cell, after H+ has been pumped out?
-increase in charge difference stimulates cations to enter the cell
-this decreases Ψs = water moves into cell = increase in turgor pressure
what is photomorphogenesis?
changes in morphology/shape due to light intensity/wavelength/availability
what plant processes does blue light regulate?
phototropism, stomata opening/closing, and slowing of growth of seedlings out of soil
what blue light photoreceptor is responsible for phototropism?
phototropin
what blue light receptor controls the opening of stomata?
zeaxanthin
what blue light photoreceptor controls the growth of seedlings as they break the soil surface?
cryptochromes
what is a phytochrome?
a pigment with 2 different forms that responds to two types of light
what two forms of light do phytochromes respond to?
red light (Pr) and far-red light (Pfr)
what do phytochromes do when stimulated by red light and far-red light?
-red light (660nm) stimulates a switch from the inactive Pr to the active Pfd
-far-red light (730nm) stimulates a switch from the active Pfr to the inactive Pr
what is the function of Pfr?
to stimulate germination and flowering in plants, as well as stimulating flowering in long-day plants
what is the function of Pr?
to inhibit germination + flowering in plants, as well as inhibiting flowering in long-day plants
how do different flashes of red and far-red light affect a plant?
-only the last flash of light (red or far red) determines what will happen, all flashes before are invalidated
what are long-day / short-night plants?
plants that flower when the nights are shorter than a given critical period: lettuce, spinach, spring-blooming flowers
what is photoperiodism?
a physiological response of a plant with respect to the length of night
what are short-day / long-night plants?
-plants that flower when nights are longer than a certain critical period: soybeans, poinsettias, asters, fall-blooming flowers
what wavelengths of light are involved in regulating plant flowering?
red light / far-red light
what are day-neutral plants?
plants who flower regardless of day length, such as tomatoes
what is gravitropism?
the growth of plants in response to the force of gravity. can be with gravity (+, roots) or against gravity (-, shoots)
what are statoliths?
microscopic “rocks” in a plant that settle on their root downside, allowing them to sense gravity
what is thigmomorphogenesis?
changes in plant form / growth due to environmental disturbances
what is thigmotropism?
directional growth by plants in response to touch - ex - pea tendrils
what are “rapid leaf movements” with regards to thigmotropism?
acute, immediate responses by a plant to touch, such as a venus fly trap snapping shut when touched by a fly
what are pulvini cells and what is their function?
pulvini = specialized “motor organs” within a plant that can sense touch
what happens in a plant when pulvini cells sense touch?
-K+ leaves = Ψs increases = water leaves = leaves shrivel up and allow for desired movement
