AN IAA OXIDASE‐INHIBITOR SYSTEM IN BEAN PODS. I. PHYSIOLOGICAL SIGNIFICANCE AND SOURCE OF THE INHIBITOR

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Abstract
Sacher, Joseph A. (Los Angeles State Coll., Los Angeles, Calif.) An IAA oxidase‐inhibitor system in bean pods. I. Physiological significance and source of the inhibitor. Amer. Jour. Bot. 48(9): 820–828. Illus. 1961.—In ‘Kentucky Wonder’ pole bean pod segments, a correlation is shown between the resistance and susceptibility to senescence of exocarp and endocarp, respectively, in the absence of exogenous auxin, and the distribution of a natural, heat‐stable, dialyzable inhibitor of IAA oxidase. The tissues are similar in content of IAA oxidase, but the exocarp, which is resistant to senescence, has a high content of inhibitor. The endocarp, which senesces readily, has none. The greater efficacy of naphthalene acetic acid than IAA in delaying senescence of endocarp, in experiments which minimized or eliminated the effect of the destruction of IAA at cut surfaces, suggested this was due to the endogenous destruction of IAA. But the application of inhibitor did not delay senescence of endocarp. The inhibitor content of exocarp increased 2–5 fold with aging. Reaction mixtures containing non‐dialyzed exocarp enzyme solution showed no IAA destruction for 4 1/2 + hr, while with exocarp slices IAA destruction proceeded rapidly after a 10‐min lag. Evidence is presented which indicates that cytoplasmic particulates are the source of the dialyzable inhibitor.
Funding Information
  • National Science Foundation (G‐9894)