Lecture 3- Exploiting Light

Question 1

Silphium laciniatum

Answer 1

compass plant,grows leaves to face E and W, leaves move in late morning to keep away from hot midday sun

Question 2

Phototropism

Answer 2

chloroplasts movement in response to light

Question 3

Heliotropism

Answer 3

movement with sun, plants keeping track of sun

Question 4

2 requirements for seeds of temperate grasslands and weeds to germinate

Answer 4

1. seed must be buried for some time

2. seed needs exposure to light

Question 5

light signal transport to nucleus

Answer 5

light to cytoplasm to signal to nucleus

Question 6

Nucelopore

Answer 6

proteins at entrance that screen compounds

Question 7

3 Types of barrier that nuclear membrane is

Answer 7

physical, chemical, energy driven

Question 8

Nuclear membrane energy-driven

Answer 8

entrance and exit, uses GTP instead of ATP

Question 9

Running out of GTP

Answer 9

plant cell dies, human cell gets diseases

Question 10

Light receptor molecules

Answer 10

all are proteins

Question 11

Types of receptors to blue or UV wavelengths

Answer 11

cry-1, cry-2, phototropin

Question 12

Types of receptors to red/far-red wavelengths

Answer 12

phytochromes

Question 13

Phytochrome movement

Answer 13

induced by light, moves from cytoplasm into nucleus

Question 14

Blue light receptor protein movement

Answer 14

only found within nucleus, only move within nucleus

Question 15

5 Types of Phytochromes

Answer 15

PHYA, PHYB, PHYC, PHYD, PHYE

Question 16

Phytochrome synthesis

Answer 16

in the dark, at time of manufacture in cell they are produced in inactive form (Pr), ready to absorb red light

Question 17

Phytochrome exposure to red light

Answer 17

Changes shape to phyiologically active form (Pfr) which moves into nucelus, found by studies with flourescnet tag

Question 18

PhyA abundance

Answer 18

dark-grown plants

Question 19

Location of Pr form of PHYA

Answer 19

cytoplasm, sticking to outer edge

Question 20

What happens when Pfr moves into nucleus

Answer 20

alters gene expression

Question 21

Nuclear Localization Signal

Answer 21

code that is part of PHYA a.a sequence, allows PHYA to pass through nucleopore into nucleus. recognized by nucelopore proteins

Question 22

PHYA signal cascades in cytoplasm

Answer 22

very low fluence response (moonlight response)
high irradiance response (short pulses of intense light)
continuous red light response (uninterrupted red light) (only in experimental conditions)

Question 23

PHYB

Answer 23

receptor for classical red/far red responses, has NLS

Question 24

Red light wavelength

Answer 24

650-670nm

Question 25

Far-red light wavelength

Answer 25

705-740nm

Question 26

Reversal of effect of red light

Answer 26

far-red light

Question 27

Germination occurs if

Answer 27

last light was red

Question 28

No germination if

Answer 28

last light was far-red

Question 29

Red:far-red on forest floor,growth form

Answer 29

red

Question 30

Red:far-red in the open, growth form

Answer 30

1:1, squat and branched

Question 31

Light perception

Answer 31

PHYB

Question 32

Malvastrum rotundifolium

Answer 32

spotted mallow. leaves face rising sun, follow sun during day, return to original position at night

Question 33

plants that move to follow sun

Answer 33

sunflower, soybean, cowpea, cotton

Question 34

Harnessed plants experienced

Answer 34

lower leaf temp, fewer/smaller seeds

Question 35

How does Pfr turn back to Pr

Answer 35

protein turnover and enzymatic degradation Pfr degrades faster than Pr autoconversion of Pfr to Pr

Question 36

Neutral

Answer 36

day length insensitive, tomatoes and dandelions flower all season

Question 37

long day plants

Answer 37

only flower if number of hours of daylight/day exceeds threshold. lettuce and spinach flower in spring (longer days)

Question 38

Short day plants

Answer 38

only flower if # of hours of daylight/day is less than certain number eg soybeans and chrysanthemums flower in late summer (shorter days)

Question 39

Harry Allard and Wightman Garner experiment

Answer 39

Biloxi soybeans-5 weeks earlier | Maryland Mammoth tobacco-3 months earlier

Question 40

Pigeon pea (Cajanus cajan)

Answer 40

short day plant, genetically altered to lose shortday requirement

Question 41

Chrysanthemum

Answer 41

short day plant, flowering delayed by flashes of light in night. daylength altered with blackout curtains to produce them year round