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Plant hormones

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Hormones

from Gr. to excite

natural chemicalmessengerstransported totarget cells

minuteconcentrations =substantial change

growth regulators

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Plants respond to stimuli

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Plant hormones coordinate growth,development and responses to stimuli

Tropisms

growth responses

organs curvetowards (+) oraway from (-) astimulus

ex. phototropism,thigmotropism,

gravitropism

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Studies on phototropism

towards or away fromlight

differential growth ofcells on opposite sidesof a shoot or coleoptile

cells on darker sideelongate faster thanthose on the light side

experiments by Darwinand son and FW Went

due to auxindistributions

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Went experiment

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