Auxin molecules act to cause plant tropisms by congregating on the side away from the stimulus.
Auxins are one of the plant hormones that functions in cell elongation.
Auxins cause the movement of plant parts called tropism by congregating on one side of the plant, hence, causing that side to grow more and elongate than the other side.
Therefore, auxin molecules act to cause plant tropisms by congregating on the side away from the stimulus.
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