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Plant Responses

Plant Responses. How plants move. www.wou.edu/~bledsoek/103materials/.../ Plant _ responses .ppt. Early Inquiry. The houseplant observation. For years, people noticed that houseplants tended to lean toward a source of light.

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Plant Responses

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  1. Plant Responses How plants move www.wou.edu/~bledsoek/103materials/.../Plant_responses.ppt

  2. Early Inquiry

  3. The houseplant observation • For years, people noticed that houseplants tended to lean toward a source of light. • Charles Darwin and his son Francis, wondered why. How does a plant “know” where to lean?

  4. Tropisms • Tropisms are the growth of a plant toward or away from a stimulus, including: • Phototropism: in response to light • Gravitropism: in response to gravity • Thigmotropism: in response to touch

  5. Tropisms: cell elongation • In general, tropisms involve cell elongation or suppression of cell elongation on one side of a plant, causing the plant to grow in a particular direction.

  6. Phototropism • Look at the sprouts in the bottom picture and the explanatory diagram at the top. Explain why the sprouts are all leaning in the same direction.

  7. Gravitropism • In this Impatiens plant, shoots grow upwards and roots grow downwards in response to gravity. • On which side of the shoot and root do you think auxins are more concentrated?

  8. Thigmotropism • In some plants, vining stems or tendrils will grow in response to touch. • Which side of the tendril is elongating? Where might the auxin be? (Remember, this is the shoot system.)

  9. Nastic movement in the sensitive plant (Mimosa pudica)

  10. Other examples • Sunflowers follow the sun during the day. • Leaves of many plants turn to follow the sun.

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