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Response of Eastern Gamagrass Seed to Gibberellic Acid Buffered below Its pKa


This article in CS

  1. Vol. 43 No. 3, p. 927-933
    Received: Apr 3, 2002

    * Corresponding author(s): adknapp@iastate.edu
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  1. X. Tiana,
  2. A. D. Knapp *a,
  3. L. R. Gibsona,
  4. R. Struthersa,
  5. K. J. Moorea,
  6. E. C. Brummera and
  7. T. B. Baileyb
  1. a Dep. of Agronomy, Iowa State Univ., Ames, IA 50011
    b Dep. of Statistics, Iowa State Univ., Ames, IA 50011


Eastern gamagrass [Tripsacum dactyloides (L.) L.] seed are usually dormant, often causing seedling establishment difficulties. This study was conducted to assess the effect of gibberellic acid (GA3) buffered below its pKa (3.8) on seed germination of eastern gamagrass. In one experiment, concentrations of 0.001-, 0.005-, and 0.01 M buffered GA3 solutions were applied to seed with cupules removed from six commercial seed lots produced in three different years. After 28 d of germination, GA3 application increased total seed germination by 25 to 47 percentage points. The three GA3 concentrations were equally effective in promoting germination in all seed lots except one, where 0.001 M GA3 was more effective than 0.01 M GA3 The germination rate was accelerated by GA3 application during the germination process but did not result in germination of all the viable seeds. An average 10% of the viable caryopses remained dormant at the end of the germination test. A second experiment evaluated the germination of intact cupules after treatment for 24 or 48 h in distilled water, 0.001 M GA3 solution, buffer solution, or buffered 0.001 M GA3 solution. Buffered GA3 was not effective at enhancing germination of eastern gamagrass seed when cupules were left intact. These results suggest that there may be multiple dormancy mechanisms in eastern gamagrass. At least one mechanism involves the caryopsis and is affected by GA3 application. Furthermore, the cupule-mediated dormancy mechanism(s) and the caryopsis-mediated mechanism(s) must be addressed to obtain complete germination of dormant seed.

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Copyright © 2003. Crop Science Society of AmericaPublished in Crop Sci.43:927–933.