Morphogenesis in the Mycelium: Control of Lateral Hypha Frequency in Mucor hiemalis by Amino-Acids

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Abstract
A method is described for the perfusion of growing mycelial margins with solutions and for the measurement of their effect upon the frequency of lateral hypha production. Perfusion with water induces in Mucor hiemalis Wehm. a high lateral branch frequency which is only moderately diminished if a minerals+ thiamin+ glucose solution is used. Additions of various materials to this basal solution may promote or strongly depress lateral branching. Internode lengthening agents are enzymic digest of casein, or its acid hydrolysate or dialysate, at pH 50. About half the activity of casein hydrolysate is found with favourable mixtures of amino-acids, and with arginine or lysine. Some degree of activity is also found with six other amino-acids alone, Ca(NO2)2, uracil plus adenine, and other as yet unidentified materials. Internode shortening effects are demonstrated for five amino-acids and asparagine. Evidence is given of interactions between acids. Growth of the fungus for 14 hours removes the internode lengthening quality from dilute malt-extract medium, and during the same time its α amino nitrogen is markedly reduced. Various inactive materials are mentioned and possible mechanisms of activity are discussed.