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28 Cards in this Set
- Front
- Back
How do plants respond to environmental cues:
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1) through evolution (very long term)
2) growth differences (trees vs. wind; yrs) 3) change developmental processes (make roots or leaves, wks) 4) change physiological processes (CAM responds to day vs. night) |
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What controls responses over the course of a plants life?
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hormones
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what are hormones?
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chemical produced in one part of body and affects another part of the body.
- actions are specific and they affect specific tissues - active in minute concentrations. |
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Who discovered the first hormone?
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Darwin and Darwin
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What was the first hormone discovered?
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the hormone responsible for phototropism
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coleoptile:
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grows straight up in normal overhead light and in the dark
- grows toward light when the light comes form one side. |
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define tropisms:
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growth responses towards or away from a stimulus
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what are 3 examples of tropisms?
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1) gravitropism
2) phototropism 3) thigmotropism |
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define thigmotropism:
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directional growth in response to touch.
- touching a plant at a site, has been demonstrated to slow growth at that site. ----- if one side of a vine or tendril is touching something.... that side will grow slowly and the other side will grow more quickly |
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What is thought to be the cause of thigmotropism?
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an increased ethylene in response to mechanical stimulation ---> decreased cell elongation at site of stimulation
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define circadian rhythm:
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responses that are based on a 24 hr. time period.
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define biological clock:
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the internal clock that allows circadian rhythms to occur.
- are usually set by the light/dark cycle of the sun. |
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what do biological clocks modulate (control)?
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- metabolism/ metabolic rate
- cell division rate - blood cell deposition into blood stream - alertness etc.... |
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In plants what do biological clocks modulate (control)?
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- metabolism/ metabolic rate
- opening and closing of stomata - legume sleep movement - long term growth responses to day length etc.... |
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define photoperiodism:
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responses dependent on day vs. night length.
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Plants need to be able to tell when the change of seasons occur for.... in other words photoperiodism controls?
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- seed germination
- flowering - entering or breaking winter or summer dormancy |
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what is photoperiod?
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the determination of relative length of day vs. night.
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Describe the best studied example of photoperidism
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study used a variety of mutant tobacco (Maryland mammoth)
- it grew tall in summer, but would not flower during the summer, finally flowered in dec. in a greenhouse. - found that it was short winter days that induced plant to flower. ---- by manipulating the daylight period so that the day was 14hrs. or shorter, they were able to induce flowering. |
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What is the mutant tobacco called a short day plant?
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because it was a shortened day that induced flowering.
ex: soy and poinsettias. |
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what are some plants called long day plants?
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because they flower when days are longer than a certain period of time.
ex: plants that flower in the summer, spinach flowers... |
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What are day neutral plants?
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plants that flower at a certain maturity stage and are not photoperiodic
ex: tomato |
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it was discovered that it was not day length but actually _______ length that was the controlling factor in photoperiodism plants.
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night length
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flowering and night length:
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Phytochrome:
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- a light absorbing protein pigment
- exist in leaves - the protein is a dimer and an enzyme and it exists in 2 states. - can be turned on and off by red light. |
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what occurs when phytochrome is flashed with red light at night?
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the night is interrupted and flowering is inhibited.
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What occurs if the phytochrome is shined with red light twice?
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what does photoreversible mean?
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Describing any compound or system that can exist in two forms, and can be changed from one to the other by the appropriate influence of light.
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Phytochromes allow plants to adapt to certain conditons such as and fine tuning of?
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- day/night length
- light intensity - light quality (wavelength) fine tuning of: - flowering time - growth spurts - breaking dormancy - seed germination |