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Inhibition of Root Growth and Cation Uptake by Antibiotics¹

ABSTRACT

Microbial products of an antibiotic nature produced in the rhizosphere may affect root growth and development. Twenty newer antibiotics have been tested to determine their activity in repressing elongation of roots of cucumber and growth of barley roots as measured by weight changes. Potency in repressing root elongation was found in most; 7 caused 50% repression at concentrations < 10 µg. per ml. Effects on conversion of barley seed endosperm to roots were demonstrated at similar but not identical concentrations. Effects on cation accumulation by excised 5-day-old barley roots were studied using various antibiotic concentrations in 10^-3M K₂SO₄. In no case was uptake found to be more sensitive than growth, and, with 4 of the 5 antibiotics studied, significant repression of uptake was observed only at concentrations many fold greater than those repressing growth.

¹ Paper No. 19 from the Plant Nutrition Laboratory, The University of Michigan, Ann Arbor. Presented in substance before Div. III, Soil Science Society of America, Aug. 6, 1958, at Lafayette, Ind.

² Professor of Botany, The University of Michigan.

Received for publication January 22, 1959. Accepted for publication February 18, 1959.