Are gibberellins capable of replacing the environmental flowering signal?

Flowering is a complex cascade of processes that occurs in response to envi ronmental signals such as photoperiod, temperature, light intensity, and sp ectrum. Gibberellins (GAs) are known to be able to replace some of these si gnals and induce flowering. The degree of substitution is not consistent, a nd sometimes the same GA is very effective in one species and inhibitory in another. A group of scientists constructed synthetic, custom-made GAs that promoted flowering and did not affect elongation in a few species. These s ynthetic GAs were tried on several long-day (LD) commercial cut flowers in order to enhance blooming. It was found that in aster, phlox, and limonium, all quantitative LD plants, endo-16,17-dihydro-GA(5) was able to enhance f lowering. In solidago and hypericum, mandatory LD plants, this compound cou ld not replace the LD requirement and blooming date was similar to control plants in solidago and marginally enhanced in hypericum. On the other hand, GA, enhanced flowering in solidago but delayed blooming in hypericum. The reasons for different patterns of influence in different species are discus sed.