EXPERIMENT
   Researchers  exposed  maize  (Zea  mays)  coleoptiles to light to test
   which wavelengths stimulate the phototropic bending toward light.
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RESULTS
   Curvature occurred with wavelengths below 500 nm and was greatest with
   blue light.
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CONCLUSION
   Phototropism  is  caused  by a photoreceptor that is sensitive to blue
   light.