Chapter 39 Vocab - Summary Campbell Biology PDF

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Chapter 39: Plants Responses to Internal and External Signals 39.1 “Signal transduction pathways link signal reception to response” 

Etiolation- morphological adaptations for growing in darkness

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De-etiolation- when a shoot reaches the sunlight and undergoes profound changes such as slowing elongation of stem, leaves expanding, roots elongating, and the shoot producing chlorophyll Transduction

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Second Messengers- small, internally produced chemicals that transfer and amplify the signal from the receptor to other proteins that cause the response 39.2 “Plant hormones help coordinate growth development, and responses to stimuli”

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Hormones- chemicals signals that coordinate the different parts of an organism; a signaling molecule that is produced in tiny amounts by one part of an organism's body and transported to other parts, where it binds to a specific receptor and triggers responses in target cells and tissues The Discovery of Plant Hormones

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Tropism- any growth response that results in plant organs curving away or toward from stimuli

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Phototropism- the growth of a shoot toward or away from light (positive phototropism for toward and negative phototropism for away) A Survey of Plant Hormones Auxin

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Auxin- a term used for any chemical substance that promotes elongation of coleoptiles; the natural auxin in plants is indoleactic acid (IAA)

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Expansins- enzymes that break the cross-links (hydrogen bonds) between cellulose microfibrils and other cell wall constituents, loosening the wall’s fabric in response to the acidification of the wall Cytokinins

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Cytokinins- growth regulators that stimulate cytokinesis; the most common is zeatin because it was first discovered in maize Gibberellins

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Gibberellin- a chemical that has a variety of effects in plants such as stem elongation, fruit growth, and seed germination Brassinosteroids

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Brassinosteroids- steroids that are chemically similar to cholesterol and sex hormones of animals. They induce cell elongation and division in stem segments and seedlings at concentrations as low as 10^-12 M; similar to auxins, but are different Abscisic Acid

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Abscisic acid (ABA)- ABA slows growth, it often antagonizes the actions of growth hormones, and the ration of ABA to one or more growth hormones determines the final physiological outcome Ethylene

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Ethylene - active factor in illuminating gas; produced by plants in response to stresses such as flooding, mechanical pressure, injury, and infection. Production

also occurs in fruit ripening and programmed cell deal and in response to high concentrations of externally applied auxin 

Triple Response- enables the shoot to avoid the obstacle. Three parts of this response area slowing of stem elongation, a thickening of the stem (which makes it stronger), and a curvature that causes the stem to start growing horizontally

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Aptosis- programmed cell death 39.3 “Responses to light are critical for plant success”

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Photomorphogenesis - effects of light on plant morphology

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Action Spectrum- depicts the relative effectiveness of different wavelengths of radiation in driving a particular process

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Blue-Light Photoreceptors- absorb mostly red light; initiates phototropism, the light-induced opening of stomata, and the light-induced slowing of hypocotyl elongation that occurs when a seedling breaks ground

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Phytochromes- absorb mostly red light; play a role in seed germination and shade avoidance Biological Clocks and Circadian Rhythms

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Circadian Rhythms- cycles of a frequency of 24 hours not directly controlled by any known environmental variables Photoperiodism and Responses to Seasons

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Photoperiodism- a physiological response to photoperiod, such as flowering Photoperiodism and Control of Flowering

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Short-Day Plant- plants that require a light period shorter than a critical length to flower; usually flower in later summer, fall or winter

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Long-Day Plants- plants that generally flower in late spring or early summer. E.g. Spinach

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Day-Neutral Plants- unaffected by photoperiods, flower when they reach a certain stage of maturity, regardless of day length. Egg. Tomatoes, rice, and dandelions

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Vernilization- pretreatment with cold to induce flowering A Flowering Hormone?

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Florigen- the flowering signal, not yet chemically identified 39.4 “Plants respond to a wide variety of stimuli other than light” Gravity

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Gravitropism- plants adjusting growth in response to gravity; roots display positive gravitropism and shoots exhibit negative gravitropism

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Statoliths- specialized plastids containing starch grains to allow plants to detect gravity Mechanical Stimuli

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Thigmomorphogenesis- changes in form that result from mechanical perturbation

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Thigomotropism- the directional growth in response to touch

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Action Potentials- impulses that resemble slow nerve impulses in animals Environmental Stresses

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Abiotic- nonliving

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Biotic- living Heat Stress

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Heat-Shock Proteins- proteins which help protect other proteins from heat stress 39.5 “Plants defend themselves against herbivores and pathogens”

Defenses Against Herbivores 

Jasmonic Acid- an important molecule in plant defense against herbivores Defenses Against Pathogens Gene-for-Gene Recognition

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Virulent- pathogens against which a plant has little specific defense

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Avirulent - strains of pathogens that are mildly harmful, but do not kill the host plant

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Gene-for-gene Recognition - a widespread form of plant disease resistance that involves recognition of pathogen derived molecules by the protein products of specific plant disease resistance R genes Plant Responses to Pathogen Invasions

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Elictors- molecules that induce a broad type of host defense response

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Oligosaccharins- a type of elictor that is derived from cellulose fragments released by cell wall damage

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

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PR proteins- a protein involved in plant responses to pathogens (PR = pathogenesis-related)

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Hypersensitive Response (HR) - A plant's localized defense response to a pathogen Systemic Acquired Resistance

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Systemic Acquired Resistance (SAR) - a defensive response in infected plants that helps protect healthy tissue from pathogenic invasion

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Salicylic Acid - a plant hormone that may be partially responsible for activating systemic acquired resistance to pathogens...