Changes in the Levels of Endogenous Growth Regulators during Development of the Flowers of Chrysanthemum morifolium

Gibberellin-like substances and an auxin similar to IAA weredetected by bioassays in extracts of flowers of Chrysanthemummorifolium. The activity of these substances was shown to reacha maximum early in the development of the flower when its relativegrowth-rate was at a maximum, and then to decline with the relativegrowth-rate. The leaves of lateral flowering shoots were found to containgibberellins similar to those detected in the flowers whilea different gibberellin, which appeared to decrease in activitywith the age of the shoot, was detected in the stem. An auxinsimilar to indol-3yl-acetic acid (IAA) was also detected inthese stems. Growth-promoting substances were not detected inthe old stems and leaves from the main shoot. Gas-liquid chromatographyrevealed the presence of a number of additional gibberellinsin the flowers. The chemical nature of the growth substances is discussed inrelation to their biological and chromatographic behaviour.