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24 Cards in this Set
- Front
- Back
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Plant Behavior
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Response to stimuli
Plant movements Bending, twisting or rotating |
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Responses to internal and external stimuli
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Internal
Chemical signals – hormones , phytohormones or plant growth substances |
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Environmental stimuli
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Light, atmospheric gases (CO2 and water vapor), temperature, touch, wind, gravity, water, rocks, and soil stimuli
Herbivores, pathogens, organic chemicals from neighboring plants, and beneficial or harmful soil organisms Agricultural chemicals including hormones |
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Biological environmental Plant stimuli
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Herbivores, Plant hormone applications, Pathogens, organic chemicals from other plants, microorganisms
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Plant responses
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Receptor molecules located in plant cells sense stimuli and cause responses
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Phototropism
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involves both a cellular perception of light and a growth response of stem tissue to an internal chemical signal (auxin)
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Plant signal transduction 3 parts
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Receptor activation
Transduction of the signal via second messengers Cellular response |
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Auxins
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“Master” plant hormone
Indoleacetic acid (IAA) is one plant auxin Promotes expression of diverse genes known as auxin-response genes |
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Auxin effects
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Establishes the apical-basal polarity of seed embryos
Induces vascular tissue to differentiate Mediates phototropism Promotes formation of adventitious roots Stimulates fruit development |
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Many effects of practical importance to humans
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Seedless fruit production
Stimulates flower ovaries to mature into fruits |
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Cytokinins
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vIncrease rate of cytokinesis or cell division
Root tips major production site Also produced in shoots and seeds At shoot and root tips, cytokinins influence meristem size, stem cell activity, and vascular tissue development Also involved in root and shoot growth and branching, the production of flowers and seeds, and leaf senescence (aging) |
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Gibberellins
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Produced in apical buds, roots, young leaves, and seed embryos
Foster seed germination Enhance stem elongation and flowering Retard leaf and fruit aging Arise from stimulatory effects on cell division and elongation |
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Ethylene
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Important in coordinating developmental and stress responses
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Triple response of seedlings
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Ethylene prevents the seedling stem and root from elongating
Hormone induces the stem and root to swell radially, thereby increasing in thickness Seedling stem bends so that a hook pushes up through the soil Result of an imbalance of auxin Ethylene drives auxin imbalance |
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Abscisic acid (ABA)
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Slows or stops plant metabolism when growing conditions are poor
May induce bud and seed dormancy Stimulates formation of protective scales around buds of perennial plants in preparation for winter |
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Photoperiodism
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Based on the presence of light receptors within cells
Photoreceptors respond to light absorption by switching on signal transduction Results in sun tracking, phototropism, flowering and seed germination |
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Long-day plants
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flower in spring or early summer, when the night period is shorter (and thus the day length is longer) than a defined period
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Short-day plants
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flower only when the night length is longer than a defined period such as in late summer, fall, or winter, when days are short
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Day-neutral plants
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flower regardless of the night length, as long as day length meets the minimal requirements for plant growth
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Gravitropism
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Growth in response to the force of gravity
Shoots are said to be negatively gravitropic Most roots positively gravitropic |
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Thigmotropism
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Touch responses
Roots encounter rocks as they grow down |
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Flooding
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Too much water makes roots unable to obtain sufficient oxygen
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Pathogen and herbivore attack
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Structural barriers (cuticles, epidermal trichomes, and outer bark) help to reduce infection and herbivore attack
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Hypersensitive response (HR)
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Occurs when a plant recognizes a pathogen by chemical means and responds in such a way that the disease symptoms are limited
Several components including increased production of hydrogen peroxide Nitric oxide also produced |
