Gibberellins and Light Inhibition of Stem Growth in Peas

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Abstract
Two fractions with gibberellin-like activity were obtained from dwarf peas by means of partition chromatography and thin-layer chromatography. No differences could be detected in the levels of these substances when extracted from light- and dark-grown plants. One of the 2 gibberellin-like fractions (fraction II) behaved chromatographically and biologically like gibberellin A1 (GA1), the other (fraction I) like gibberellin A5 (GA5). Fraction II and GA1 were highly active on dwarf peas grown in light and in darkness. Fraction I and GA5 were highly active in the dark but 10 times less active when the test plants were exposed to red light. In light-grown Alaska peas GA5 was half as active as GA1 in promoting stem elongation. Again both gibberellins were equally active when applied to etiolated Alaska peas. It is concluded that illumination lowers the sensitivity of the tissue to fraction I and to GA5 while not affecting the sensitivity to fraction II and GA1. It is estimated that the reaction affected by light is 5 times more sensitive to irradiation in dwarf peas than in Alaska peas. It is probable that fraction I is identical with GA5 and fraction II identical with GA1.