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The Action of Duramycin on Plant Roots¹

ABSTRACT

The polypeptide antibiotic, duramycin, has been reported to be antagonistic to certain plant pathogens. Growth of plant roots, however, is repressed by this compound. The duramycin concentration causing 50% reduction in elongation of the primary root of cucumber is 42 µg. per ml. The deleterious effect is mitigated or prevented by simultaneous presentation of calcium or magnesium ions. Depending on concentration, duramycin resembles polymyxin in being bound to plant roots. Roots exposed to excess duramycin lose solutes, both inorganic and organic, and are irreversibly injured. Auxin-induced water uptake by hypocotyl segments is unaffected by low concentrations of duramycin which does not have antiauxin properties.

¹ Paper No. 23 from the Plant Nutrition Laboratory, The University of Michigan, Ann Arbor. Able assistance in these experiments was provided by Mrs. Elvera B. Shappirio. Presented before Div. III, Soil Science Society of America, Nov. 18, 1959, at Cincinnati, Ohio.

² Professor.

Received for publication June 12, 1959. Accepted for publication November 20, 1959.