Evaluation of the present information on the mechanisms leading to flower bud induction, evocation and differentiation in olea europaea

7 páginas, 1 figura, 2 tablas, 16 referencias.-- The "5th International Symposium on Olive Growing" will be held in Izmir, Turkey between 26 September- 2 October, 2004.-- Fué leído en el citado simposio por Shimon Lavee y por motivos desconocidos no figura en el libro de actas.

The lack of regularity in reproductive organ development leading in many cases to severe alternate bearing is one of the major problems and drawbacks in today’s economy of the olive industry. Although a considerable amount of work has been devoted during the second half of the last century to this subject, our understanding of the metabolism leading to flower bud differentiation and ability to control alternate bearing is still limited. The genetic potential to induce flower buds is environmentally dependent. Temperature was found the most eminent environmental factor to affect the metabolism leading to flower bud induction. Specific but not yet clearly defined temperatures in early summer on one hand and relatively low winter temperature gradually fluctuating with warm ones in the winter are essential for inducing the metabolic pass-ways initiating the sequence of processes leading to the formation of flower buds. Changes in the RNA content of lateral buds expected to develop inflorescences in the spring was shown to occur already in the fall. Thus, some workers suggested that the low winter temperatures act as a dormancy breaking agent of pre differentiated buds. On the other hand, these same buds were shown to grow vegetative when induced without or with unsuitable winter temperature. This could be explained as dedifferentiation process however, no differentiated floral organs have been found in buds in the fall and no aborted secondary growing points in lateral buds have been found either. The presently available data indicate that neither summer-fall nor mid winter seasons could be individually responsible for flower bud initiation. The presently developing fruits on the trees were found to have a major affect on controlling the metabolism leading to reproductive development although they were shown to have no effect on the tree’s carboydrate level and only a minor one on the nitrogen balance. However, the protein composition of leaves on fruiting and non fruiting trees was found to be different with specific proteins developing in leaves of the fruiting trees and others on the non fruiting ones. Furthermore, chlorogenic acid, related to the cinnamic acid pass-way was found to accumulate in leaves of fruiting trees and to inhibit specifically winter differentiation. The messenger from the developing fruits to change the leaf metabolism is not yet entirely clear but believed to be specific gibberellins. Based on the present available data including the effect of harvest time on the following reproductive development and the amount of yield on vegetative growth, a two phase mechanism for reproductive bud development in the olive could be suggested. The initial developing bud of the olive is suggested to be indifferent. During the “off” year, when tha plant has normalized its situation after a heavy crop, the buds receive their initial induction to develop reproductive. Those buds which received their initial induction to differentiate reproductively will respond to the winter inductive conditions.

Peer reviewed