Light

Question 1

Photomorphogenesis

Answer 1

effects of light on plant morphology

Question 2

phototropism

Answer 2

directional growth in response to light

Question 3

What do plants detect

Answer 3

light direction, intensity, and wavelength

Question 4

Action spectrum

Answer 4

depicts relative response of a process to different wavelengths

Question 5

What are the classes of light receptors

Answer 5

Blue-light photoreceptors and phytochromes

Question 6

Blue-light photoreceptors

Answer 6

control hypocotyl elongation
Control stomatal opening
Control phototropism

Question 7

Phytochromes

Answer 7

Pigments that regulate many of a plant’s responses to light throughout its life
Seed germination
shade avoidance
Etiolation (shoot elongation)

Question 8

what system provides the plant with information about the quality of light

Answer 8

phytochrome system

Question 9

Shaded plants receive far more _____ than ____ light

Answer 9

far-red, red

Question 10

Shade avoidance response

Answer 10

the phytochrome ratio shifts in favor of Pr when a tree is shade

Question 11

Circadian rhythms

Answer 11

cycles that are about 24 hours long and are governed by an “internal clock”

Question 12

What may the internal clock depend on

Answer 12

synthesis of a protein regulated through feedback control and may be common to all eukaryotes

Question 13

Photoperiod

Answer 13

the relative lengths of night and day

Question 14

what is the environmental stimulus plants use most often to detect time of year

Answer 14

Photoperiod

Question 15

Phytochrome conversion

Answer 15

marks sunrise and sunset, providing the biological clock with environmental cues

Question 16

Photoperiodism

Answer 16

a physiological response to photoperiod

Question 17

Short-day plants

Answer 17

Flower when light period is shorter than a critical threshold

Question 18

Long-day plants

Answer 18

flower when a light period is longer than a certain number of hours

Question 19

Day-neutral plants

Answer 19

flowering is controlled by plant maturity, not photoperiod

Question 20

what are short-day plants governed by

Answer 20

whether the critical night length sets a minimum number of hours of darkness

Question 21

what are long-day plants governed by

Answer 21

whether the critical night length sets a maximum number of hours of darkness

Question 22

Flowering Locus C (FLC)

Answer 22

Discovered in Arabidopsis thaliana
FLC activation inhibits flowering
MADS box gene
Controls vernalization
Epigenetic control regulates the gene
Cold exposure reduces expression

Question 23

florigen

Answer 23

the flowering signal

Question 24

what are florigens

Answer 24

may be a macromolecule governed by the CONSTANS gene

Question 25

what must happen for a bud to form a flower instead of a vegetative shoot

Answer 25

meristem identity genes must first be switched on

Question 26

Gravitropism

Answer 26

Response to gravity

Question 27

what kind of gravitropism do roots show

Answer 27

positive gravitropism

Question 28

what kind of gravitropism do shoots show

Answer 28

negative gravitropism

Question 29

statoliths

Answer 29

specialized plastids (amyloplasts) containing dense starch grains

Question 30

what may contribute to gravity detection

Answer 30

dense organelles, in addition to starch granules

Question 31

Thigmomorphogenesis

Answer 31

refers to changes in form that result from mechanical disturbance

Question 32

Thigmotropism

Answer 32

movement of ions induces osmotic potential change

Question 33

What are the responses to drought

Answer 33

``` reduce transpiration by closing stomata slow leaf growth reduce exposed surface area growth of shallow roots is inhibited deeper roots continue to grow ```

Question 34

Response to flooding

Answer 34

enzymatic destruction of root cortex cells creates air tubes that help plants survive oxygen deprivation during flooding

Question 35

Response to herbivory

Answer 35

thorns and distasteful or toxic compounds | Some plants "recruit" predatory animals that help defend against specific herbivores

Question 36

Responses to high temps

Answer 36

produce heat shock proteins (HSPs) if exposed to rapid temperature increases Can survive otherwise lethal temperatures if they are gradually exposed to increasing temperature

Question 37

HSPs

Answer 37

stabilize other proteins

Question 38

Thermotolerance

Answer 38

the gradual exposure of plants to high temperatures

Question 39

Responses to chilling

Answer 39

Lipid composition of a plant's membranes can help predict whether the plant will be sensitive or resistant to chilling Supercooling - survive as low as -40 C Limits ice crystal formation to extracellular spaces Antifreeze proteins

Question 40

The more unsaturated the membrane lipids are,

Answer 40

the more resistant the plant is to chilling