Ap Biology Chapter 39 Vocabulary

Front 1

abiotic

Back 1

Nonliving.

Front 2

abscisic acid (ABA)

Back 2

A plant hormone that slows down growth, often antagonizing actions of growth hormones. Two of its many effects are to promote seed dormancy and facilitate drought tolerance. Produced in the terminal bud and slows down growth and directs leaf primordia to develop into the scales that will protect the dormant cells during winter.

Front 3

action potential

Back 3

A rapid change in the membrane potential of an excitable cell, caused by stimulus-triggered, selective opening and closing of voltage-sensitive gates in sodium and potassium ion channels. Electrical impulses in plants similar to nervous system in animals.

Front 4

action spectrum

Back 4

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

Front 5

apoptosis

Back 5

The changes that occur within a cell as it undergoes programmed cell death, which is brought about by signals that trigger the activation of a cascade of suicide proteins in the cell destined to die.

Front 6

auxin

Back 6

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. Any chemical substance that promotes the elongation of celeoptiles  

Front 7

avirulent

Back 7

A term describing a pathogen that can only mildly harm, but not kill, the host plant.

Front 8

biotic

Back 8

Pertaining to the living organisms in the environment.

Front 9

blue-light photoreceptors

Back 9

A class of light receptors in plants. Blue light initiates a variety of responses, such as phototropism and slowing of hypocotyl elongation.

Front 10

brassinosteroids

Back 10

Steroid hormones in plants that have a variety of effects, including cell elongation, retarding leaf abscission, and promoting xylem differentiation.

Front 11

circadian rhythm

Back 11

A physiological cycle of about 24 hours that is present in all eukaryotic organisms and that persists even in the absence of external cues.

Front 12

cytokinins

Back 12

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.

Front 13

day-neutral plant

Back 13

A plant whose flowering is not affected by photoperiod.

Front 14

de-etiolation

Back 14

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

Front 15

elicitor

Back 15

A molecule that induces a broad type of host defense response.

Front 16

ethylene

Back 16

The only gaseous plant hormone. Among its many effects are response to mechanical stress, programmed cell death, leaf abscission, and fruit ripening.

Front 17

etiolation

Back 17

Plant morphological adaptations for growing in darkness.

Front 18

expansins

Back 18

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

Front 19

florigen

Back 19

A flowering signal, not yet chemically identified, that may be a hormone or may be a change in relative concentrations of multiple hormones.

Front 20

gene-for-gene recognition

Back 20

A widespread form of plant disease resistance involving recognition of pathogen-derived molecules by the protein products of specific plant disease resistance genes.

Front 21

gibberellins

Back 21

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 stimulate fruit development with auxin.

Front 22

gravitropism

Back 22

A response of a plant or animal to gravity.

Front 23

heat-shock protein

Back 23

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

Front 24

hormone

Back 24

In multicellular organisms, one of many types of circulating chemical signals that are formed in specialized cells, travel in body fluids, and act on specific target cells to change their functioning.

Front 25

hypersensitive response (HR)

Back 25

A plant’s localized defense response to a pathogen. Localized defense response. Enhanced production of phytoalexins and PR proteins occurs and the area is "sealed off."  

Front 26

jasmonic acid

Back 26

An important molecule in plant defense against herbivores.

Front 27

long-day plant

Back 27

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

Front 28

oligosaccharin

Back 28

A type of elicitor (molecule that induces a broad defense response in plants) that is derived from cellulose fragments released by cell wall damage. Short chains of sugars released from cell walls by the hydrolytic action of enzymes on cellulose and pectin  

Front 29

photomorphogenesis

Back 29

Effects of light on plant morphology.

Front 30

photoperiodism

Back 30

A physiological response to photoperiod, the relative lengths of night and day. An example of photoperiodism is flowering.

Front 31

phototropism

Back 31

Growth of a plant shoot toward or away from light.

Front 32

phytoalexin

Back 32

An antibiotic, produced by plants, that destroys microorganisms or inhibits their growth.

Front 33

phytochromes

Back 33

A class of light receptors in plants. Mostly absorbing red light, these photoreceptors regulate many plant responses, including seed germination and shade avoidance.

Front 34

PR protein

Back 34

A protein involved in plant responses to pathogens (PR = pathogenesis-related).

Front 35

salicylic acid

Back 35

A plant hormone that may be partially responsible for activating systemic acquired resistance to pathogens.

Front 36

second messenger

Back 36

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

Front 37

short-day plant

Back 37

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

Front 38

statolith

Back 38

1) In plants, a specialized plastid that contains dense starch grains and may play a role in detecting gravity; 2) In invertebrates, a grain or other dense granule that settles in response to gravity and is found in sensory organs that function in equilibrium. Specialized plastids containing dense starch grains. Used to determine "up from down."  

Front 39

systemic acquired resistance (SAR)

Back 39

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

Front 40

thigmomorphogenesis

Back 40

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

Front 41

thigmotropism

Back 41

A directional growth of a plant in response to touch.

Front 42

triple response

Back 42

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

Front 43

tropism

Back 43

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

Front 44

vernalization

Back 44

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

Front 45

virulent

Back 45

A term describing a pathogen against which a plant has little specific defense.