, Volume 145, Issue 3, pp 269–272 | Cite as

Floral initiation in sorghum hastened by gibberellic acid and far-red light

  • Emily A. Williams
  • Page W. Morgan


Combinations of far-red light (FR) (4 min) and gibberellic acid (GA3), given at the beginning of a daily 12-h dark period in a growth room, were used to study floral induction in four maturity genotypes of the milo group of sorghum (Sorghum bicolor (L.) Moench). The 12-h dark period without GA3 application or FR induced flowering in only the early genotype; FR hastened initiation in the early genotype, while GA3 hastened floral initiation in the two intermidiate-flowering genotypes. GA3 and FR together had a strong synergistic effect, hastening floral initiation by 30 to more than 80 d in the early and intermediate genotypes. Red light (R) did not hasten flowering; FR preceded by R gave the same effect as FR alone. GA3 promoted stem elongation equally whether floral initiation occurred or not; thus, its effect on stem elongation was independent of floral initiation. The capacity of GA3 to induce flowering in sorghum, a short-day plant, seems to be enhanced by phytochrome being in the PR form at the beginning of the night when GA3 was applied.

Key words

Flowering Gibberellin Photoperiodism Phytochrome Sorghum 



far-red light




gibberellic acid


red light


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Copyright information

© Springer-Verlag 1979

Authors and Affiliations

  • Emily A. Williams
    • 1
  • Page W. Morgan
    • 1
  1. 1.Department of Plant Sciences, Texas Agricultural Experiment StationTexas A&M UniversityCollege StationUSA

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