Phototropic Dosage-Response Curves for Oat Coleoptiles

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Abstract
The coleoptile tips of 3-day-old etiolated seedlings of Avena sativa were irradiated with monochromatic blue light of 4358 A, both with and without pretreatment with red light. Phototropic curvature in degrees was plotted against log(intensity (I) x exposure time (t)) for 3 intensities. First positive and 1st negative curvatures are a function of the product (I x t) alone and are made less sensitive to phototropic induction by red light treatment. Second positive curvature depends only on t and not on the blue light intensity. Red light increases the sensitivity of the latter response to phototropic induction.