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Plants in motion


Although plants cannot move around, they can change their direction of growth or turning in response to stimuli from their surroundings. This is called tropism. Positive tropism is when a plant grows or turns toward the stimulus, and negative tropism is when a plant grows or turns away from the stimulus.


Phototropism: plant's overall growth or movement in response to light. This response is caused by the redistribution of the plant hormone auxin within the plant.
Helitropism:
(helio="sun")
plant's ability to move or grow in response to sunlight. Also called solar tracking.
Diaheliotropisim: leaves track the sun and orient themselves perpendicular to sun rays to maximize light absorbtion.
Paraheliotropism: leaves orient themselves parallel to sun rays to avoid and minimize solar radiation.
Gravitropism: plant's growth or movement in response to gravity. Auxin and calcium are involved in this response. Also called geotropism (geo="earth").
Positive gravitropism: root grows downward, responding to gravity positively.
Negative gravitropism: shoot grows upward, responding to gravity negatively.
Thigmotropism:
(thigma="touch")
plant's growth or movement in response to contact with a solid object.


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