Table I.

GA structure-activity relationships

GA-aHypocotyl Length-bGA4:APT1Ratio-cActivity-d
mm
3β-OH-GAs
 00.8  (0.1)1.00
 GA4 3.3  (0.3)n.d.-e Active
 GA1 1.0  (0.1)0.41Inactive
 GA4-Methyl ester0.7  (0.1)0.80Inactive
 GA C0.9  (0.1)0.98Inactive
Non-3β-OH-GAs
epi-GA4 2.8  (0.3)n.d.Active
 3-oxo-GA9 4.1  (0.4)n.d.Active
  • F0-a GA and analog structures as shown in Figure4.

  • F0-b Seedlings were grown on germination medium containing individual GAs or analogs at 10−7 m. Hypocotyls were measured as described in Figure 2 withse in parentheses.

  • F0-c RelativeGA4 transcript levels calculated after 22 cycles.GA4 and APT1 transcript levels were obtained initially as ImageQuant phosphor imaging values (see Methods), and are expressed as normalized GA4:APT1 ratio (gal-3 grown on germination medium only = 1).

  • F0-d Activity of each GA at 10−7 m. GA1, although classed here as inactive, has mild activity.

  • F0-e n.d., Samples where the GA4transcript level was too low to be detected, preventing calculation of the GA4:APT1 ratio. In all cases APT1 was expressed at a similar level.