Chapter 39 Reading Quiz. What are the three parts to a signal-transduction pathway? What is the general term for chemicals that coordinate the parts of an organism? Which hormone promotes the ripening of fruits? What effect do gibberellins have on seeds? What is “apoptosis”?.
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- positive towards light
- negative away from light
- auxin cannot suppress the growth of these buds once it has begun
- auxins stimulate stem elongation
- gibberellins also stimulate stem elongation
- dual control by auxins & gibberellins
- in some plants, both must be present for fruit to set
to an internal clock
21. Distinguish among short-day plants, long-day plants, and day-neutral plants; give common examples of each; and explain how they depend upon critical night length.
ex: poinsettias (flower in late summer, fall, or winter)
ex: spinach, lettuce, irises (flower in late spring, early summer)
ex: tomatoes, rice, dandelions
22. Explain how the interconversion of phytochrome can act as a switching mechanism to help plants detect sunlight and trigger many plant responses to light.
- pigments called phytochromes
24. Describe how plants apparently tell up from down, and explain why roots display positive gravitropism and shoots exhibit negative gravitropism.
ex: vine coiling response
ex: stunted trees in windy places