Chapter 39

Question 1

One of a ribosome’s three binding sites for tRNA during translation. The E site is the place where discharged tRNAs leave the ribosome. (E stands for exit.)

Answer 1

E site

Question 2

Effects of light on plant morphology.

Answer 2

photomorphogenesis

Question 3

Pathogen-encoded protein that cripples the host’s innate immune system.

Answer 3

effector

Question 4

A physiological cycle of about 24 hours that persists even in the absence of external cues.

Answer 4

circadian rhythm

Question 5

A plant that flowers (usually in late summer, fall, or winter) only when the light period is shorter than a critical length.

Answer 5

short-day plant

Question 6

A flowering signal, probably a protein, that is made in leaves under certain conditions and that travels to the shoot apical meristems, inducing them to switch from vegetative to reproductive growth.

Answer 6

florigen

Question 7

Plant enzyme that breaks the cross-links (hydrogen bonds) between cellulose microfibrils and other cell wall constituents, loosening the wall’s fabric.

Answer 7

expansin

Question 8

Any of a class of related plant hormones that retard aging and act in concert with auxin to stimulate cell division, influence the pathway of differentiation, and control apical dominance.

Answer 8

cytokinin

Question 9

Nonliving; referring to the physical and chemical properties of an environment.

Answer 9

abiotic

Question 10

A directional growth of a plant in response to touch.

Answer 10

thigmotropism

Question 11

Any of a class of related plant hormones that stimulate growth in the stem and leaves, trigger the germination of seeds and breaking of bud dormancy, and (with auxin) stimulate fruit development.

Answer 11

gibberellin

Question 12

A type of light receptor in plants that initiates a variety of responses, such as phototropism and slowing of hypocotyl elongation.

Answer 12

blue-light photoreceptor

Question 13

A signaling molecule in plants that may be partially responsible for activating systemic acquired resistance to pathogens.

Answer 13

salicylic acid

Question 14

A physiological response to photoperiod, the interval in a 24-hour period during which an organism is exposed to light. An example of photoperiodism is flowering.

Answer 14

photoperiodism

Question 15

The use of cold treatment to induce a plant to flower.

Answer 15

vernalization

Question 16

A growth response that results in the curvature of whole plant organs toward or away from stimuli due to differential rates of cell elongation.

Answer 16

tropism

Question 17

A response in plants to chronic mechanical stimulation, resulting from increased ethylene production. An example is thickening stems in response to strong winds.

Answer 17

thigmomophogenesis

Question 18

Short molecular sequences that typify certain groups of pathogens and that are recognized by cells of the innate immune system.

Answer 18

pathogen-associated molecular patterns (PAMPs)

Question 19

A gaseous plant hormone involved in responses to mechanical stress, programmed cell death, leaf abscission, and fruit ripening.

Answer 19

ethylene

Question 20

A small, nonprotein, water-soluble molecule or ion, such as a calcium ion (Ca2+) or cyclic AMP, that relays a signal to a cell’s interior in response to a signaling molecule bound by a signal receptor protein.

Answer 20

second messenger

Question 21

The growth phase in a plant or plant part (as a leaf) from full maturity to death.

Answer 21

senescence

Question 22

A protein that helps protect other proteins during heat stress. Heat-shock proteins are found in plants, animals, and microorganisms.

Answer 22

heat-shock protein

Question 23

Pertaining to the living factors—the organisms—in an environment

Answer 23

biotic

Question 24

A graph that profiles the relative effectiveness of different wavelengths of radiation in driving a particular process.

Answer 24

action spectrum

Question 25

Any of a class of plant hormones that inhibit shoot branching, trigger the germination of parasitic plant seeds, and stimulate the association of plant roots with mycorrhizal fungi.

Answer 25

strigolactone

Question 26

Plant morphological adaptations for growing in darkness.

Answer 26

etiolation

Question 27

A plant growth maneuver in response to mechanical stress, involving slowing of stem elongation, thickening of the stem, and a curvature that causes the stem to start growing horizontally.

Answer 27

triple response

Question 28

In animal behavior, a process involving transmission of, reception of, and response to signals. The term is also used in connection with other organisms, as well as individual cells of multicellular organisms.

Answer 28

communication

Question 29

A response of a plant or animal to gravity.

Answer 29

gravitopism

Question 30

Any of a class of plant hormones that regulate a wide range of developmental processes in plants and play a key role in plant defense against herbivores.

Answer 30

jasmonate

Question 31

A plant that flowers (usually in late spring or early summer) only when the light period is longer than a critical length.

Answer 31

long-day plant

Question 32

Growth of a plant shoot toward or away from light.

Answer 32

phototropism

Question 33

The changes a plant shoot undergoes in response to sunlight; also known informally as greening.

Answer 33

de-etiolation

Question 34

A defensive response in infected plants that helps protect healthy tissue from pathogenic invasion.

Answer 34

systemic acquired resistance

Question 35

A plant hormone that slows growth, often antagonizing the actions of growth hormones. Two of its many effects are to promote seed dormancy and facilitate drought tolerance.

Answer 35

abscisic acid (ABA)

Question 36

A plant in which flower formation is not controlled by photoperiod or day length.

Answer 36

Day-neutral plants

Question 37

A steroid hormone in plants that has a variety of effects, including inducing cell elongation, retarding leaf abscission, and promoting xylem differentiation.

Answer 37

brassinosteroid

Question 38

A plant’s localized defense response to a pathogen, involving the death of cells around the site of infection.

Answer 38

hypersensitive response

Question 39

A type of light receptor in plants that mostly absorbs red light and regulates many plant responses, such as seed germination and shade avoidance.

Answer 39

phytochrome

Question 40

A term that primarily refers to indoleacetic acid (IAA), a natural plant hormone that has a variety of effects, including cell elongation, root formation, secondary growth, and fruit growth.

Answer 40

auxin