Plant hormones 2

What 3 colors can plants sense

red (phytochrome), blue (cryptochrome and phototropin), and ultra-violete B lightW

What are phytochromes

photoreceptor proteins that can exists in 2 different

states based on its photochromicity (wavelength it absorbs)

What are the 2 states can phytochromes be in

Pr (ground state) and Pfr ( active state)

What does Pr absorb

red light (sunlight)

What does Pfr absorb

far-red light (shade)

What occurs when a plant is exposed to red light, is it fast or slow

Pr to Pfr, a fast process

What occurs when a plant is exposed to far-red light, is it fast or slow

Pfr-pr, a fast process

What occurs when a plant is exposed to darkness, is it fast or slow

Pfr-Pr, a slow process

How does phytochrome act in germination in darkness

red light promotes their germination

What occurs to plants that germinate in the dark

they form long weak stems with a hook below the apical meristem

When does De-etiolation occur

happens upon exposure to sunlight or red light

What is etiolation

the formation of a weak long stem with a hook below the apical meristem

What do phytochrome and cryptochromes regulate

they regulate the activity of gibberellin

What does Pfr do to Gibberellin activity

inhibits Gibberellin

What occurs to internode expansion if a plant grows in full sunlight

More Pfr causes less internode expansion

What occurs to internode expansion if a plant grows in the shade

Less Pfr thus more internode expansion

What is photoperiodism

ability of organisms to control

life processes based on changes in light

What is the most reliable environmental variable

changes in day/night

What do plants use photoperiodism to do

to determine then to flower

When do long-day plants flower

begin flowering as days get

longer (January-June in NH)

When do short-day plants flower

begin flowering as days get

shorter (July-December ni NH)

What is the key factor of flowering

the length of the night

What are nastic movements

are non-directional responses

to stimuli

What does nyctinastic refer to

to circadian rhythm-based

responses controlled by daily changes in light

What is ncytinastic movement caused by

ion transport the leads to changes in

turgor pressure in cells.

What is tropism

directional growth in response to stimuli

What is positive tropism

growth toward the stimuli

What is negative tropism

growth away from the

stimuli

What is hydrotropism

response to moisture

What is thigmotropism

response to touch

What are the portions that make up photoreceptors

protein portion and a light-absorbing portion called

chromophore

What do phototropins mediate

responses to phototropic activity in the apical meristem, absorbing blue light

What tropism do shoots show

positive

What tropism do roots show

negative

Phototropism occurs as a result of what

auxin accumulation

What causes auxins to move towards the shaded side

phosphorylation of phototropins

What is the hypothesis that auxins cause cells to activate proton pumps

acid growth hypothesis

What are statoliths

specialized amyloplasts n cells

of the stem cortex and root cap settle to the

bottom of the cell under gravity.

What do statoliths in contact with the ER do

release calcium ions

What do calcium ions promote

n accumulation of PIN

(auxin transport) proteins

What hydrotropism do root exhibit and why

positive hydrotropism, moving toward

areas of higher relative moisture

What mediates hydrotropism

receptor-like kinases

(RLKs) in the root caps

What is thigmotropism

growth that results from

constant directional pressure.

What thigmotropism do tendrils have

positive

What is positive thigmotropism mediated by

jasmonic acid

What thigmotropism do roots have

negative, as an obstruction is encounterd

What is negative thigmotropism mediated by

a spike in calcium and auxin gradiant

What thigmomorphogenesis

a slow developmental

change in the shape of a plant subjected to

continuous mechanical stress. ( mediated by ethylene and jasmonic acid)

What is thigmonastic movementa touch

a touch

response independent of the direction of stimulus.