ISHS Acta Horticulturae 482: International Symposium on Cut Flowers in the Tropics
FLOWERING CONTROL BY ARTIFICIAL GIBBERELLINS |
| Authors: | Y. Ben-Tal, Y. Erner |
| Abstract:
Gibberellins (GA) was known to be involved in flowering processes of many plants since the late 1950s and it was considered as the flowering hormone for a while. But the information was very confusing. In some plants it promoted flowering, while in others flowering was inhibited. Then, a new theory suggested that GA promoted flowering only in long day plants (LDP) or when vernalization was required. But many exceptions that contradicted this theory were accumulated. All the research work leading to the early theories that related flowering to GA were done with GA3 or by its common name "Gibberellin Acid". As more and more GAs were discovered their role in plants became more confusing. In the mid 1980s Pharis and coworkers suggested that some functional groups in the GA molecule are the control mechanism that distinguished among the different GAs regarding their function. Comparisons of different GAs revealed that GA4 was more active than GA3 in flowering promotion of woody Angiosperms, especially in Pinaceae, and apple trees while GA1 was associated with elongation. Based on these assumptions Mander synthesized GAs in which certain changes like addition of hydroxyl groups, changing bond's type etc. were introduced artificially into the molecule and were tested for their ability to promote flowering. Some of these compounds actually promoted flowering in various plants. Furthermore, elongation was not affected and sometimes even inhibited. It was the first time that flowering induced by GAs was separated from stem or inflorescence elongation. These artificial GAs promoted flowering in Lolium temulentum, Salix pentandra, Thalaspi averenze, Xanthium strumarium, Pharbitis nil, Sorghum bicolor L and we found it effective in orange, olive, grapevine and Limonium. The fact that a large number of plants had responded so far to artificial GAs, might be a beginning of a new era. We might be able to control flowering of commercial cut flowers by simple sprays. | |
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