Lecture 7

Question 1

photomorphogenesis

Answer 1

development of plant in light.

Question 2

skotomorphogenesis

Answer 2

development of plants in darkness

Question 4

etiolation

Answer 4

plants response to lack of light, resulting in lack of cotyledon and root growth. stems are rapidly developed

Question 5

de-etiolation

Answer 5

once plants reach lights after etiolation, they undergo photomorphogenesis

Question 6

negative phototropism

Answer 6

plant grows against light

Question 7

positive phototropism

Answer 7

plant grows towards light

Question 8

what colours are sensed by olants

Answer 8

blue (ultraviolet) and red

Question 10

phytochromes

Answer 10

photoreceptors in plants that detect light and regulate germination, flowering, and seedling growth

Question 11

far red light

Answer 11

converts the active form Pfr into the inactive form Pr

Question 12

Red light converts the inactive form __ to the active form ____

Answer 12

Pr, Pfr

Question 13

red light stimulates _____

Answer 13

germination

Question 14

far red lights inhibit _______

Answer 14

germination

Question 15

Pfr is the _____ form

Answer 15

active

Question 16

Pr is the ______ form

Answer 16

inactive

Question 17

plants use phytochrome to

Answer 17

• measure the red/far red ratio
• measure the length of the night, during the night, red light induced active Pfr is slowly converted into the inactive Pr form. the longer the night the less Pfr response.

Question 18

mutated phytochrome can cause hy (hypocotyl) mutants to undergo _______ under light

Answer 18

skotomorohogenesis

Question 19

______ _______ ______ mutants do not exhibit phototropism

Answer 19

non phototrophic hypocotyl

Question 20

what are photoreceptors composed of?

Answer 20

apoprotein and light sensitive chromophore pigments

Question 21

apoprotein + chromophore =

Answer 21

holoprotein

Question 22

phytochromes primarily absorb in the ____ to _____nm red light/far red light range

Answer 22

600, 700

Question 23

phototropins and cryptochromes absorb in the Uv-A to blue light range ____ to ____ nm

Answer 23

320,500

Question 24

name three photoreceptors

Answer 24

1. cryptochrome
2. phototropins
3. phytochromes

Question 25

phytochrome B is composed of

Answer 25

apoprotein and phytochromobilin chromophore.

Question 26

phytochrome is synthesized in _____

Answer 26

plastids

Question 27

phytomobilin is attached to a

Answer 27

cysteine

Question 28

2 holoproteins in a phytochrome B form a _____

Answer 28

dimer

Question 29

phytomobilin switches conformation from ____ to ____ in response to red light

Answer 29

cis, trans

Question 30

what happens when a phytochrome B is activated by red light.

Answer 30

1. D ring of phytochromobilin rotates converting from cis to trans conformation, exposing nuclear localization sequences (NLSs) within the PRD domains. 2. most of the phytochrome pool moves to the nucleus where it regulates gene expression by interacting with nuclear proteins. 3. seed germination, photomorphogenesis

Question 31

The _____/______ ratio provides plants with position and time information through phytochrome signalling

Answer 31

red/far red

Question 32

shade avoidance response

Answer 32

when plants receive a low red/far red ratio and elongates to avoid shade

Question 33

The R:FR ratio changes from ____ during daylight to ____ in the evening

Answer 33

1.15, 0.7

Question 34

in response to red light Pfr moves into the nucleus and interacts with ______ _____ _____ ______ that leads to activation of genes needed for ______

Answer 34

phytochrome B interacting factors , photomorphogenesis

Question 35

In phototropins, blue light induced change in conformation leads to _______ and ________ signalling by the kinase domains

Answer 35

autophosphorylation, phosphorylation.

Question 36

activation phototropin is reversed by the phosphatase _____

Answer 36

PP2A

Question 37

____ and ____ proteins can form mixed photobodies, generating integrated response of red and blue lights

Answer 37

phytochrome, cryptochrome

Question 38

phytochrome and cryptochrome for complexes called _____ in the nucleus

Answer 38

photobodies

Question 39

name one far red receptor

Answer 39

phytochromes (PHY)

Question 40

name two Blue and ultraviolet receptors

Answer 40

phototropin (PHOT), chryptochrome (CRY)

Question 41

an example of phototropin action

Answer 41

signal transduction leading to stomatal opening in response to blue light.

Question 42

when a phototropin absorbs blue light, a signal transduction chain leads to:

Answer 42

the closure of anion channels, and opening of potassium channels - elevated intracellular ion levels - water uptake my osmosis - swelling and bending of cells - opening between cells for gas exchange

Question 43

how do phytochrome and cryptochrome proteins interact to generate a combined red and blue light response for photogenesis

Answer 43

they combine to form photobodies which changes chromatin packaging, therefore changing gene expression to regulate photomorphogenesis