Lecture 5

Question 1

true or false; plants can “see” light

Answer 1

true

Question 2

What does plants seeing light affect

Answer 2

germination
seedling development
phototropism
photosynthesis 
shade avoidance
flowering 
circadian rythmns
photmorphogenesis

Question 3

What does it mean by photomorphogenesis

Answer 3

creation of form in the light

Question 4

define nutation

Answer 4

circular swaying movement of the tip of growing shoot

Question 5

true or false; light induces morphological changes in seedlings

Answer 5

true

Question 6

What do you call the creation of form, of seedlings grown in the dark

Answer 6

skotomorphogenesis or etiolation

Question 7

describe the characteristics of the seedlings grown in the dark

Answer 7

tall
leaves are yellow green
chloroplasts are not properly developed
little chlorphyll
leaves are not fully expanded or open

Question 8

What do you call the creation of form in the light

Answer 8

photomorphogenesis

Question 9

What happens eg. in potatoes when the growing conditions of plants are shifted from dark to light

Answer 9

plants undergo de-etiolation

• sprouting potatoes in the dark
• shoots greening up in the light

Question 10

Why is harmful to eat green potatoes

Answer 10

solanine is present in the green areas

• can occur in improperly stored potatoes
• solanine is harmful when ingested and can be toxic in large quantities

Question 11

true or false; environment has the a large effect on the expression of a plants’ genes

Answer 11

true

Question 12

define germination

Answer 12

beginning of growth by seed

Question 13

define photosynthesis

Answer 13

conversion of light energy to chemical energy

Question 14

true or false; wavelengths and the light intensity that plants perceive have a great impact on their growth

Answer 14

true

Question 15

What wavelength affects photosynthesis

Answer 15

400-700nm is photosynthetically active radiation

Question 16

What does it mean by phototropism

Answer 16

growth towards the light

Question 17

What wavelength and light color affects phototropism

Answer 17

• blue light causes plant to bend towards the light
• multiple photoreceptors are involved in detecting the blue light
• experiment called: determining the action spectrum (allows us to determine the wavelength perceived by a plant)

Question 18

what light causes plants to grow out of the shade and into the light

Answer 18

far red light

Question 19

what light do green leaves absorb

Answer 19

red light

• increases the proportion of far red light relative to red light
• this is detected by the plants and they grow to taller to out compete other plants

Question 20

What are the light receptors in humans

Answer 20

humans have 4 light receptor pigments

• 3 for each of the primary colors in our cone cells in the retina
• 1 in our rod cells

Question 21

true or false; plants also have many photoreceptors for blue and red light

Answer 21

true

Question 22

What are phototropins

Answer 22

detect blue light

Question 23

what are phytochromes

Answer 23

detect red light

Question 24

What are cryptochromes

Answer 24

detect blue light

Question 25

Describe the structure of phytochromes

Answer 25

- is a dimer - 2 identical proteins that are dimerized together to become one big molecule - each protein has a domain ( 2 domains in total); for photoreceptor activity and kinase activity - each molecule is attached to a chromophore - activated by light

Question 26

What is a chromophore

Answer 26

detects light | organic molecule

Question 27

true or false; there are two forms of phytochrome that absorb different wavelengths

Answer 27

true

Question 28

What are the two forms of phytochrome

Answer 28

Pr (660 nm) | Pfr (730nm)

Question 29

What does Pr absorb

Answer 29

red light

Question 30

what does Pfr absorb

Answer 30

far red light (longer wavelength)

Question 31

true or false; phytochrome is a molecular switching mechanism

Answer 31

true

Question 32

true or false; Pfr is the biologically active form of phytochrome

Answer 32

true

Question 33

what reverses phytochrome

Answer 33

light

Question 34

What happens in the dark to Pfr

Answer 34

slowly reverses to Pr | - slowly degraded and made

Question 35

what are the applications of studying light regulation of plant development

Answer 35

designing | selecting crops that can cope with being crowded

Question 36

true or false; most leaves are specialized for light absorption

Answer 36

true | - like a solar panel, leaves are often broad and flat to optimize light harvesting

Question 37

how come modern maize plants can be planted at high density; increasing their yield per hectare

Answer 37

Plants selected by plant breeders have upright leaves to help capture sunlight energy under crowded conditions. They can be machine planted at high density (up to 100 000 plants per hectare)

Question 38

What is the effect of red light

Answer 38

increased germination inhibit stem elongation and lateral root formation stimulates leaf expansion, cholorplast development, red flower coloration, spore germination

Question 39

What is the effect of far red light

Answer 39

inhibits germination

Question 40

what is the photoreceptor responsible for perceiving red and far red light

Answer 40

phytochrome

Question 41

What does the kinase domain trigger

Answer 41

triggers kinase cascade | of downstream events

Question 42

What are phototropism involved in

Answer 42

phototropism

Question 43

what is the survival advantage of etiolation

Answer 43

increases the plants' chances of reaching light before their stored energy supplies are exhausted