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Plant Responses. How plants move and communicate. Tropisms. Tropisms are the growth of a plant toward or away from a stimulus, including: Phototropism: in response to light Gravitropism (geotropism): in response to gravity Thigmotropism : in response to touch - PowerPoint PPT Presentation
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PLANT RESPONSES How plants move and communicate
TROPISMS Tropisms are the growth of a plant toward
or away from a stimulus, including: Phototropism: in response to light Gravitropism (geotropism): in response to
gravity Thigmotropism: in response to touch
Auxins are plant growth hormones that promote elongation of cells
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.
PHOTOTROPISM Look at the sprouts in the bottom picture
and the explanatory diagram at the top.
GRAVITROPISM In this 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?
GRAVITROPISM IN ROOTS
In roots, however, auxin concentration on the lower side of the root suppresses cell elongation.
The upper side of the root continues to grow, causing the roots to bend downward.
THIGMOTROPISM In some plants,
vining stems or tendrils will grow in response to touch.