Gibberellin-like substances in Bryophyllum daigremontianum and the distribution and persistence of applied gibberellin A3.

Acidic extracts of the long-short-day plant Bryophyllum daigremontianum contain two gibberellin (GA)-like substances called fractions I and II. In plants under permanent short-day (SD) conditions the levels of both I and II are very low. In continuous long days (LD) the total GA content is approximately 20 times higher than in SD, mainly due to an increased level of II. Extracts of plants induced to flower by the shift LD→SD show a further increase in the level of II. Application of GA3 to plants in SD causes normal flower formation, but the level of fraction II remains as low as in vegetative plants in permanent SD.Approximately 10% of the GA3 applied could still be recovered from leaves and inflorescences after 45 days, indicating that GA3 is very stable in Bryophyllum, Most of the GA3 recovered was still associated with the treated leaves, but small amounts could be detected in other leaves and in inflorescences. Results of grafting experiments indicate that these low levels of GA3 are adequate to induce production of the floral stimulus.