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This article in CS

  1. Vol. 21 No. 6, p. 818-822
    Received: Sept 4, 1980



Preflowering Levels of Phytohormones in Sorghum II. Quantitation of Preflowering Internal Levels1

  1. J. R. Dunlap and
  2. P. W. Morgan2



Levels of free and bound indole-3-acetic acid (IAA), abscisic acid (ABA), and gibberellin-like (GA-like) compounds were determined over a 25-day period prior to flowering in the above ground portions of an intermediate (60M) and a late (90M) maturing genetic line of Sorghum bicolor (L.) Moench.This was an initial effort to learn something about the hormone status of these lines on a whole shoot basis and there is no specific inference to the mechanism of photoperiodism. Following purification of the plant extract, IAA and ABA were analyzed with high performance liquid chromatography (HPLC); GA-like substances were assayed with the lettuce hypocotyl elongation bioassay. The preflowering levels of GA-like activity did not differ significantly between the two sorghum genotypes; however, the preflowering levels of both free IAA and ABA consistently increased with age in the later maturing genotype (90M). Increasing levels of free IAA and ABA relative to GA-like activity may partially account for the delayed flowering characteristic of 90M. The differences in phytohormone levels in closely related genotypes differing in photoperiod requirement for floral initiation suggest the need for a detailed examination of the phytohormone status of the sorghum maturity genotypes relative to the mechanism of photoperiodism.

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