Plant Responses to Stimuli

Question 1

What are the mechanisms of signaling

Answer 1

Reception, Transduction, Response

Question 2

Reception

Answer 2

Internal and external signals are detected by receptors, proteins that change in response to specific stimuli

Question 3

Transduction

Answer 3

Second messengers transfer and amplify signals from receptors to proteins that cause responses

Question 4

Response

Answer 4

A signal transduction pathway leads to regulation of one or more cellular activities
In most cases, these responses to stimulation involve increased activity of enzymes
This can occur by transcriptional regulation or post translational modification

Question 5

Specific transcription factors

Answer 5

bind directly to specific regions of DNA and control transcription of genes

Question 6

Positive transcription factors

Answer 6

proteins that increase the transcription of specific genes, while negative transcription factors are proteins that decrease the transcription of specific genes

Question 7

Post-translational modification

Answer 7

modification of existing proteins in the signal response

Question 8

What does modification often involve

Answer 8

the phosphorylation of specific amino acids

Question 9

Phototropism

Answer 9

a plant’s response to light

Question 10

Auxin

Answer 10

any chemical that promotes elongation of coleoptiles

Question 11

Indoleacetic acid (IAA)

Answer 11

a common auxin in plants

Question 12

Role of auxin transporter proteins

Answer 12

move the hormone from the basal end of one cell into the apical end of the neighboring cell

Question 13

What is the role of auxin in cell elongation

Answer 13

auxin stimulates proton pumps in the plasma membrane
Proton pumps lower the pH in the cell wall, activating expansions, enzymes that loosen the wall’s fabric
With the cellulose loosened, the cell can elongate

Question 14

How does auxin affect secondary growth

Answer 14

by inducing cell division in the vascular cambium and influencing differentiation of secondary xylem

Question 15

What are two kinds of synthetic auxins

Answer 15

Naphthalene acetic acid (NAA) and indolebutyric acid (IBA)

Question 16

What do synthetic auxins do

Answer 16

prevent abscission in apples and berries

Promote flowering and fruiting in pineapples

Question 17

2,4-dichlorophenoxyacetic acid (2,4-D)

Answer 17

a herbicide commonly used to kill weeds

Question 18

What do cytokinins do

Answer 18

stimulate cytokinesis

Question 19

Where are cytokinins produced

Answer 19

in actively growing tissues such as roots, embryos , and fruits

Question 20

what is the role of cytokinins

Answer 20

work together with auxin to control cell division and differentiation
Retard the aging of some plant organs by inhibiting protein breakdown, stimulating RNA and protein synthesis, and mobilizing nutrients from surrounding tissues

Question 21

Control of Apical Dominance

Answer 21

Cytokinins, auxin, and other factors interact in the control of apical dominance, a terminal bud’s ability to suppress development of axillary buds

Question 22

What happens if the terminal bud is removed

Answer 22

the plants become bushier

Question 23

Strigolactones

Answer 23

Inhibit axillary bud growth
Affect extent of branching
Derived from caretonoid

Question 24

Role of Gibberellins

Answer 24

Stem Elongation, Fruit growth, Germination

Question 25

Stem Elongation

Answer 25

Gibberellins stimulate growth of leaves and stems

In stems, they stimulate cell elongation and cell division

Question 26

Fruit growth

Answer 26

In many plants, both auxin and gibberellins must be present for fruit to set
Gibberellins are used in spraying of Thompson seedless grapes

Question 27

Germination

Answer 27

After water is imbibed, release of gibberellins from the embryo signals seeds to germinate

Question 28

Brassinosteroids

Answer 28

chemically similar to the sex hormones of animals

induce cell elongation and division in stem segments

Question 29

Abscisic Acid (ABA)

Answer 29

slows growth
Seed dormancy
Primary internal signal that enables plants to withstand drought

Question 30

Seed dormancy

Answer 30

ensures that the seed will germinate only in optimal conditions
In some seeds, dormancy is broken when ABA is removed by heavy rain, light, or prolonged cold
Precocious germination is observed in maize mutants that lack a transcription factor required for ABA to induce expression of certain genes
Primary internal signal that enables plants to withstand drought

Question 31

Ethylene

Answer 31

Produced in response to stresses such as drought, flooding, mechanical pressure, injury, and infection

Question 32

Effects of ethylene

Answer 32

response to mechanical stress
senescence
leaf abscission
fruit ripening

Question 33

What does ethylene induce

Answer 33

the triple response, which allows a growing shoot to avoid obstacles

Question 34

What does the triple response consist of

Answer 34

slowing of stem elongation
thickening of the stem
horizontal growth

Question 35

Senescence

Answer 35

the programmed death of plant cells or organs

A burst of ethylene is associated with apoptosis

Question 36

apoptosis

Answer 36

the programmed destruction of cells, organs, or whole plants

Question 37

Leaf Abscission

Answer 37

A change in the balance of auxin and ethylene controls leaf abscission

Question 38

Fruit ripening

Answer 38

triggered by a burst of ethylene production (one bad apple spoils the bunch)