Evidence for "gibberellin-like" Substances from Flowering Plants.

Gibberellins are compounds that produce a wide variety of growth responses in flowering plants. Among these responses are stimulation of shoot growth for many plant species,' root elongation in maize,2 induction of bolting and flowering in some biennial and long-day plants,3-resumption of normal growth in certain genetically dwarfed genotypes of maize,6 growth stimulation in dwarf strains of peas and beans,7 and the overcoming of physiological dwarfing of apple seedlings.8 Gibberellins also stimulate parthenocarpy in tomatoes,9 promote the germination of light-requiring lettuce seed in the dark,'0 and reverse the light inhibition of pea stem growth."I For the interpretation of these and other effects, it is important to know whether gibberellins or "gibberellin-like" substances occur naturally in flowering plants. The three known gibberellins, gibberellic acid (gibberellin A3), Cj9H2206; gibberellin A (gibberellin Al), C19H2406; and gibberellin A2, C19H2606, are products of certain strains of the imperfect stage of the fungus Gibberella fujikuroi (Saw.) Wr.12-B6 No other organism has been found to contain these compounds. The present paper will report evidence for the occurrence of "gibberellin-like" substances from species of several different families of flowering plants.'7 These substances produce the same growth response in maize dwarfs as do the known gibberellins. RJ values for these substances will also be reported and compared with those for the known gibberellins.