Ch. 39 Key Concepts: - Signal transduction pathways link signal reception to response. - Plant hormones help coordinate growth, development, and responses to stimuli. - Responses to light are critical for plant success. - Plants respond to a wide variety of stimuli other than light. - Plants respond to attacks by herbivores and pathogens.
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| 6283022140 | etiolation | morphological adaptations for growing in darkness |  | 0 |
| 6283022141 | de-etiolation | The changes a plant shoot undergoes in response to sunlight; also known informally as greening. | 1 | |
| 6283022142 | phytochrome | plant pigment responsible for photoperiodism (sleeping at night, waking up at day, for plants) | 2 | |
| 6283022143 | second messengers | Small, non-protein water soluble molecules or ions that send messages throughout the cells by diffusion. | 3 | |
| 6283022144 | Plant growth regulator | Organic compounds other than nutrients (like hormones that affect plant growth. | 4 | |
| 6283022145 | plant hormone | abscisic acid, auxin, cytokinins, ethylene, gibberellins act as chemical messengers | 5 | |
| 6283022146 | tropism | A growth response that results in the curvature of whole plant organs toward or away from stimuli owing to differential rates of cell elongation. | 6 | |
| 6283022147 | phototropism | Growth of a plant shoot toward or away from light. | 7 | |
| 6283022148 | auxin | Indoleacetic acid (IAA), a natural plant hormone that has a variety of effects, including cell elongation, root formation, secondary growth, and fruit growth. | 8 | |
| 6283022149 | expansins | Plant enzymes that break the cross-links (hydrogen bonds) between cellulose microfibrils and other cell wall constituents, loosening the walls fabric. | 9 | |
| 6283022150 | cytokinins | A class of plant hormones that retard aging and act in concert with auxin to stimulate cell division, influence the pathway of differentiation, and control apical dominance. | 10 | |
| 6283022151 | gibberellin | a hormone that stimulates plant stem elongation | 11 | |
| 6283022152 | brassinosteroids | steroid hormones in plants that have a variety of effects, including cell elongation, retarding leaf abscission, and promoting xylem differentiation. | 12 | |
| 6283022153 | abscisic acid (ABA) | a plant hormone that slows growth, often antagonizing the actions of growth hormones. Two of its many effects are to promote seed dormancy (prevents seeds from germinating at incorrect time) and facilitate drought tolerance, high ___ causes stomata to close | 13 | |
| 6283022154 | ethylene | The only gaseous plant hormone. Among its many effects are response to mechanical stress, programmed cell death, leaf abscission, and fruit ripening. | 14 | |
| 6283022155 | triple response | 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. | 15 | |
| 6283022156 | senescence | A gradual physical decline that is related to aging and during which the body becomes less strong and efficient. | 16 | |
| 6283022157 | apoptosis | Process of programmed cell death | 17 | |
| 6283022158 | photomorphogenesis | Effects of light on plant morphology (the form of the plant). | 18 | |
| 6283022159 | action spectrum | A profile of the relative performance of the different wavelengths in photosynthesis (so green light is less absorbed, others are better absorbed). | 19 | |
| 6283022160 | blue-light photoreceptors | a type of light receptor in plants that initiates a variety of responses, such as phototropism and slowing of hypocotyl elongation | 20 | |
| 6283022161 | phytochromes | A class of light receptors in plants. Mostly absorbing red light, these photoreceptors regulate many plant responses, including seed germination and shade avoidance. | 21 | |
| 6283022162 | circadian rhythms | The 24-hour biological cycles found in humans and many other species. | 22 | |
| 6283022163 | photoperiodism | A physiological response to photoperiod, the relative lengths of night and day. An example of photoperiodism is flowering. | 23 | |
| 6283022164 | short-day plant | A plant that flowers only when the light period is shorter than a critical length. Usually fall or winter. | 24 | |
| 6283022165 | long-day plant | A plant that flowers only when the light period is longer than a critical length. Usually spring or early summer. | 25 | |
| 6283022166 | day-neutral plants | are not affected by the length of day | 26 | |
| 6283022167 | vernalization | The use of cold treatment to induce a plant to flower. | 27 | |
| 6283022168 | florigen | A flowering signal, not yet chemically identified, that may be a hormone or may be a change in relative concentrations of multiple hormones. | 28 | |
| 6283022169 | gravitropism | A growth response to gravity | 29 | |
| 6283022170 | statoliths | specialized plastids containing dense starch grains, that let plants know up from down. | 30 | |
| 6283022171 | thigmomorphogenesis | A response in plants to chronic mechanical stimulation, resulting from increased ethylene production. An example is thickening stems in response to strong winds. | 31 | |
| 6283022172 | thigmotropism | A growth response to touch | 32 | |
| 6283022173 | action potential | A neural impulse; a brief electrical charge that travels down an axon. | 33 | |
| 6283022174 | abiotic stresses | Stresses that come from non-living factors such as wind, temperature, drought or pollution | 34 | |
| 6283022175 | biotic stresses | Stresses caused by living factors, such as bacteria, fungi, animals, other plants. | 35 | |
| 6283022176 | heat-shock proteins | Proteins that help maintain integrity of other proteins that would normally be denatured in extreme heat. | 36 | |
| 6283022177 | virulent pathogens | pathogens against which a plant has little specific defense | 37 | |
| 6283022178 | avirulent pathogens | strains of pathogens that are mildly harmful, but do not kill the host plant | 38 | |
| 6283022179 | hypersensitive response | a plant's localized defense response to a pathogen, involving the death of cells around the site of infection | 39 | |
| 6283022180 | systemic acquired resistance | A defensive response in plants infected with a pathogenic microbe; helps protect healthy tissue from the microbe. | 40 |
