Lateral bud

Cytokinins were discovered in the 1950s. In combination with auxin, they control cell division, promote juvenility or slow ageing and induce the formation of lateral buds (Figure 5.3). 

A dominance hierarchy also exists within individual sinks. When the level of photosynthate is high, lateral buds on the tubers begin to develop and act as competing sinks (Tsvetoukhine, 1960). Development of lateral buds results in tubers with a highly irregular form and reduced value for many uses. 

Branching of a plant occurs when lateral buds, which become dormant shortly after formation in the leaf axil, lose their dormaney and resumed growing. Lateral buds tend to remain dormant as long as the apical bud is active and growing apical dominance), but... 

Other processes involve an antagonistic action of auxin vs. cytokinin as well. For example, studies with transgenic plants containing genes for enhanced synthesis of either auxin or cytokinin has shown that both apical dominance and xylem development depend on the relative amounts of these hormones [32]. Enhanced auxin increases apical dominance and xylem formation, while enhanced endogenous cytokinin promotes the outgrowth of lateral buds, leading to a more branched plant, and decreased xylem development. 

ABA was originally discovered because of its role in the dormancy of apical buds [20]. The correlation between the amount of ABA in apical buds and the depth of winter dormancy suggests that ABA plays a major role in the dormancy of this region. More controversial is the question as to whether ABA is involved in lateral bud dormancy as well [85]. Another major role of ABA is to induce the dormancy in maturing seeds of many species. At the same time, ABA induces the synthesis of proteins stored in seeds as... 

Subsequent work with lAA indicated that this auxin which was produced at the terminal bud stimulated cellular growth in the terminal bud but as it was transported down the shoot, somehow supressed growth of the lateral buds (22). There are indications that under the influence of auxin, the cells around lateral buds produce ethylene. It is the ethylene in turn which inhibits the growth of the lateral buds (23). When the terminal bud is removed and the auxin and ethylene are no longer present, the lateral buds grow, resulting in bushy plants. The number of flowers on the plant is also increased. 

As the tree grows in height (primary growth), branching is initiated by lateral bud development. Knots are the... 

In nature, auxins are produced in apical and root meristems, young leaves, seeds and developing fruits, and their main functions are cell elonj tion and expansion, suppression of lateral buds, etc. (Opik RoUe, 2005). In somatic embryogenesis this is considered one of the most important elements producing cell polarity and asymmetrical cell division. In general, relatively high auxin concentrations (2,4-D, lAA, etc.) favor callus formation and the induction process (cell polarity). Afterwards, when the induction stage has been achieved, it is necessary to reduce or eliminate the auxins in order to initiate the bilateral symmetry and the expression of the somatic embryos. 

BAP riboside, a synthetic cytokinin, supplied via the root system induced some effects in the shoot which are characteristic of the leaf curl syndrome, especially release of lateral buds from apical dominance and hyponasty. 

In the 1930s the inhibition of the growth of lateral buds by the terminal bud in young plants was shown to be carried out by auxin, using the following sequence of experiments [9] ... 

Removal of this apical bud allowed rapid elongation of the lateral buds previously inhibited and... 

It was not until 1968 that Burg and Burg [3] offered the basis of such an explanation. They noted firstly that applied auxin was known to promote the liberation of ethylene in seedlings. Secondly, in their experiments the ethylene was mainly localized at the nodes, and thirdly, applied ethylene inhibited lateral bud development in decapitated pea seedlings. They therefore suggested that the bud inhibition that resulted when lAA was applied to decapitated plants could be actually due to the ethylene production that was induced. 

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