20. Signals from Sunlight

Question 1

photomorphogenesis

Answer 1

effect of light on plant development and growth

Question 2

photoreceptors

Answer 2

detect and interpret light signals, initiate signal transduction pathways which ultimately trigger developmental responses

Question 3

3 types of photoreceptors

Answer 3

phototropins
cryptochromes
phytochromes

Question 4

which photoreceptors respond to blue light?

Answer 4

phototropins and cryptochromes

Question 5

which photoreceptors respond to red light?

Answer 5

phytochromes

Question 6

which photoreceptors would be most likely to detect light in the 400-500 nm wavelength range?

Answer 6

cryptochromes and phototropins

Question 7

which photoreceptors would be most likely to detect light in the 650-720 nm wavelength range?

Answer 7

phytochromes

Question 8

phytochromes are mostly used for:

Answer 8

photoperiodism

Question 9

photoperiodism

Answer 9

the timing of plant processes in relation to the year

Question 10

cryptochromes are primarily used for:

Answer 10

plant developement and photomorphogenesis, de-etiolation

Question 11

phototropins are primarily used for:

Answer 11

phototropism and chloroplast relocation

Question 12

in the stem, phototropins will be more active on the ___ side

Answer 12

sunny

Question 13

in a stem, phototropins will be less active on the ___ side

Answer 13

shady

Question 14

more active phototropins on the ___ side of the stem cause concentration of ____ on the shady side, leading to ____ of cells. This is called ___

Answer 14

sunny ; auxin ; elongation ; positive phototropism

Question 15

etiolation

Answer 15

stems kept in the dark will grow long in search of light and lack chlorophyll
once it is exposed to light it will focus on leaf development

Question 16

bending towards the light is is a ___ light response

Answer 16

blue

Question 17

high light activates phototrpins to ___ stomata

Answer 17

close

Question 18

which photoreceptor is most important for stomatal operature?

Answer 18

phototropins

Question 19

which photoreceptor is most important for chloroplast relocation?

Answer 19

phototropins

Question 20

which photoreceptor is most important for photoperiodism?

Answer 20

phytochromes

Question 21

which photoreceptor is most important for de-etiolation?

Answer 21

cryptochrome

Question 22

what is the most reliable trigger for photoreceptors?

Answer 22

length of day

Question 23

short day and long day plants are actually sensing night or day length?

Answer 23

night length

Question 24

why is night length important for plants?

Answer 24

during nighttime, Pfr –> Pr
it is the amount of Pfr that induces/inhibits flowering in plants, depending on whether they are SD/LN or LD/SN

Question 25

what light is between 620 - 750 nm wavelength?

Answer 25

red

Question 26

what light is between 700-780 nm wavelength?

Answer 26

far red

Question 27

two forms of phytochrome are:

Answer 27

Pr (red light sensitive) and Pfr (far red sensitive)

Question 28

light activates P__ to convert to P __

Answer 28

Pr –> Pfr

Question 29

during nighttime, P__ converts/decays to P__

Answer 29

Pfr –> Pr

Question 30

short nights/long day plants flower if P_ is __

Answer 30

Pfr is high

less has decayed to Pr overnight

Question 31

long nights/short day plants flower if P_ is __

Answer 31

Pfr is low

more has decayed to Pr overnight

Question 32

in short night plants, Pfr __ flowering
in long night plants, Pfr __ flowering

Answer 32

induces

inhibits

Question 33

ratio of R:FR light indicates to plants:

Answer 33

orientation

Question 34

under a canopy, there is less ___ light

Answer 34

green/blue/red

Question 35

under a canopy, there is proportionally high __ light

Answer 35

far red

Question 36

high far red : red light indicates to a plant that it is:

Answer 36

under a canopy
or has many neighbors that the FR is reflecting off of

Question 37

high far red tells plants to _____ and inhibits _____

Answer 37

grow taller ; seed germination

Question 38

phyochrome is a chromoprotein:

Answer 38

it has a pigment and a protein

Question 39

far red - enriched light stimulates plants to:

Answer 39

increased stem elongation

Question 40

far red light ___ seed germination

Answer 40

inhibits

Question 41

inhibition of seed germination from ___ light can be reversed by ___ light

Answer 41

far red ; red