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Agronomy Journal Abstract -

Manipulation of Sorghum Growth and Development with Gibberellic Acid1


This article in AJ

  1. Vol. 69 No. 5, p. 789-793
    Received: May 17, 1976

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  1. Page W. Morgan,
  2. F. R. Miller and
  3. J. R. Quinby2



This study is the initial step in an effort to understand the nature of the hormone involvement in the genetic control of height, date of flowering, and tillering in Sorghum bicolor L. Moench. The objective of these experiments was to characterize the response of sorghum genotypes varying in dwarfing genes to gibberellic acid. Since height influences commercial production, better understanding of its control may have practical and scientific value. Solutions of GA3 were applied in the whorl of vegetative plants and the growth and development of treated plants compared to controls. Sorghum grown in the field on Norwood fine sandy loam (Typic Udifluvente) soil exhibited a range of responses to gibberellic acid (GA3). Plant height of seedlings was universally promoted, but higher GA3 levels were required to increase final stem height. At concentrations up to 10−3 M GA3, stem height of members of the milo and kafir groups was promoted to a major degree and the Redlan varieties were promoted to a slight extent while hegaris were not changed. GA3 applied over a period of several weeks drastically reduced tillering and adventitious root development. Early termination of GA3 application resulted in subsequent promotion of tillering. It was possible to separate the effect of GA3 on tillering from its effect on stem height. At higher concentrations both processes are modified while at lower treatment rates GA3 reduced tillering without promoting stem height. The treatments employed did not significantly shift the date of anthesis. Several of these results were verified by experiments in a greenhouse and in the field at a different location on Hollister clay loam (Pachic Paleustoll) soil. The results support the conclusion that gibberellins function in the control of height and tillering in the genotypes studied.

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