Chapter 39: Plant Responses to Internal and External Signals

Question 1

Leaf Abscission

Answer 1

when a plant drops its leaves

Question 2

cytokinin

Answer 2

plant hormones that influence growth and the stimulation of cell division (can slow aging of plant organs)

Question 3

Auxin

Answer 3

a plant hormone which causes the elongation of cells in shoots and is involved in regulating plant growth

Question 4

ethylene

Answer 4

plants produce this in response to stresses such as

drought, flooding, mechanical pressure, injury, and infection

Question 5

xanthophylls

Answer 5

class of oxygen-containing carotenoid pigments (cause orange pigment)

Question 6

Plants sense a diverse array of

stimuli including:

Answer 6

Light
Gravity
Touch, wind
Drought, floods
Temperature
Heavy metals
Herbivores, pathogens

Question 7

Photomorphogenesis

Answer 7

development of form and structure in plants which is affected by light, other than that occurring for photosynthesis

Question 8

Gravitropism

Answer 8

important plant growth response to the environment that directs shoots upward and roots downward

Question 9

Thigmotropism

Answer 9

the turning or bending of a plant or other organism in response to a touch stimulus

Question 10

Thigmomorphogenesis

Answer 10

the response by plants to mechanical sensation (touch) by altering their growth patterns

Question 11

Response to drought

Answer 11

Abscisic acid (ABA) production, reducing water loss by closing stomata

Question 12

Response to flooding

Answer 12

Formation of air tubes that help roots survive oxygen deprivation; stimulates ethylene

Question 13

Response to salt

Answer 13

Avoiding osmotic water loss by producing solutes tolerated at high concentrations

Question 14

Response to heat

Answer 14

Synthesis of heat-shock proteins, which reduce protein denaturation at high temperatures

Question 15

Response to cold

Answer 15

Adjusting membrane fluidity; avoiding osmotic water loss; producing antifreeze proteins

Question 16

Plants counter herbivory with…

Answer 16

physical defenses, such as thorns and trichomes, and chemical defenses, such as distasteful or toxic compounds

Question 17

hypersensitive response

Answer 17

a form of cell death often associated with plant resistance to pathogen infection

Question 18

systemic acquired resistance

Answer 18

a plant defense response that provides long-lasting, broad-spectrum pathogen resistance to uninfected systemic leaves following an initial localized infection

Question 19

signal transduction pathway

Answer 19

a mechanism linking a mechanical or chemical stimulus to a specific cellular response

Question 20

Transcriptional regulation

Answer 20

end products of signal transduction pathway increase or decrease the rate of transcription of specific genes

Question 21

Post-translational modification

Answer 21

end products of signal transduction pathway modify existing proteins to make them more or less active

Question 22

Two major classes of light receptors:

Answer 22

blue-light photoreceptors (detect/respond to blue light) and phytochromes (detect/respond to red and far red light)

Question 23

Chlorophyll absorbs ____ and ____ wavelengths

Answer 23

red, blue

Question 24

Seed germination occurs during ____ illumination

Answer 24

red light

Question 25

phytochrome system

Answer 25

provides the plant with information about the quality of light

Question 26

Photoperiod

Answer 26

relative lengths of night and day

Question 27

Photoperiodism

Answer 27

a physiological response to photoperiod

Question 28

Short-day plants

Answer 28

governed by minimum number of hours of darkness

Question 29

Long-day plants

Answer 29

governed by maximum number of hours of darkness

Question 30

Day-neutral plants

Answer 30

flowering is controlled by plant maturity

Question 31

It is the length of ______ that plays the most crucial role in flowering

Answer 31

darkness

Question 32

De-etiolation

Answer 32

“greening”

Question 33

Etiolation

Answer 33

plant morphological adaptations for growing in the darkness

Question 34

tropism

Answer 34

response of a plant organ toward or away from a stimulus

Question 35

acid growth hypothesis

Answer 35

auxin stimulates proton pumps in the plasma membrane & loosens cellulose

Question 36

Gibberellins

Answer 36

stimulate growth of leaves and stems

Question 37

Abscisic acid (ABA)

Answer 37

slows growth by antagonizing the actions of the growth hormones—auxins, cytokinins, and gibberellins

Question 38

Two effects of ABA

Answer 38

Seed dormancy

Drought signaling