Changes in Endogenous Growth Substances during Flower Development.

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Abstract
Substances of the auxin and gibberellin type were extracted from lyophilized stem tips of Rudbeckia speciosa, a long-day plant, the Japanese variety Shuokan of Chrysanthemum morifolium, a cold-requiring, day-neutral plant, and the variety Shasta of C. morifolium, a short-day plant; extraction with cold, absolute methanol and ascending chromatography on Whatman 3MM paper strips in 80% isopropanol; bioassay of the various portions of the chromatograms with the mesocotyl test and the "Avena leaf test". Among the 6 different growth substances separated, the 3 major ones were: B (Rf around 0.2, active in both bioassays), C (Rf around 0.3, active in the mesocotyl test), E (Rf around 0.7, active in both bioassays). None of these substances was identical with indole-3-acetic acid, its nitrite or ethyl ester, nor with gibberellin A1 nor gibberellic acid. . The quantitative changes in these substances during flower initiation and development were as follows: In Rudbeckia, C decreased steadily after an initial rise to 10 times its original concentration reached after 1 week of long days (LD); B reached its peak after 2 weeks and E after 3 weeks of LD. In the Shuokan chrysanthemum, C decreased steadily during the vernalization treatment, B reached its peak 1 week and E 3 weeks after the beginning of the cold treatment. In both Rudbeckia and Shuokan, the sudden peak in E just preceded the capacity to bolt. In the Shasta chrysanthemum, an inhibitor moving at the E position on the chromatograms obscured the results. In Shasta, the trends of changes in the B and C substances were comparable to those in the 2 other species, but much delayed in time.