Apical Dominance and Tissue Abscission Plant Apical Dominance Auxin is synthesized in large quantities in the apical shoots of plants and moves basipetally (towards the base of the stem) throughout the plant. This auxin flow has the effect of encouraging the elongation of stem cells and at the same time inhibiting the growth of shoots in the leaf axils (lateral shoots). This results in rapid upward growth. This state is calledapical bud dominance. Whether a plant branches or not usually depends on the amount of auxin produced in the apical bud. The development of lateral shoots can not only be Stimulated by removing the apical shoot, but also by providing certain chemical compounds or by providing a certain physical environment that can reduce the plant's auxin content. Pruning shoots to overcome apical dominance is applied in plant cultivation practices with the aim of shaping the plant or making it grow "bushy". Providing auxin to plants that have been pruned can also inhibit the development of lateral shoots, a situation similar to apical shoot dominance. Thus the lateral buds remain dormant. One of the responses of plant tissue to auxin treatment is random cell division, which results in cell multiplication. This kind of unorganized or slightly organized collection of cells is calledcallus. Injured or cut stems are often found to form callus when treated with auxin. Abscission of Plant Tissue Various parts or organs of plants can experience abscission (abortion). For example leaves, branches or twigs, corollas, flowers and fruit. This process is under the influence of auxin. Abscission of leaves (and other plant parts) occurs due to differentiation taking place in a certain cell layer (abscission area) at the base of the petiole, followed by the dissolution (disappearance) of concentrated compounds so that the cells are separated from one another, except for vascular tissue cells. Next, the leaves will fall mechanically, either due to gravity or due to wind, rain and so on. The formation of the abscission area is influenced by the flow (supply) of auxin from the leaf blade to the stem. As long as the auxin supply is sufficient, abscission areas do not form. However, if this auxin supply is reduced or lost due to various reasons (aging leaves, leaf blades are damaged or die gradually) then abscission areas begin to form. The fact that auxin can control the abscission process makes it possible measures to control leaf, flower and fruit drop. Now various methods have been widely used in cultivated plants, both to stimulate and inhibit abscission. To prevent cabbage leaf abscission during harvest, 2,4-D spraying with a concentration of 25 ppm can be used. Fall of apples that are ripening can be inhibited by spraying NAA 5-10 ppm. Apart from that, several actions are taken to reduce the auxin content in the organ, so that abscission is accelerated. For example, to make it easier to harvest cotton mechanically, before harvest, cotton plants are sprayed with certain compounds that can kill the leaves. It's different with fruit plants that bear too much fruit. To achieve optimum fruit production (so that the plants do not languish), plants can be sprayed with 10-20 ppm NAA when the flowers bloom. Allegedly, that with This treatment delays the normal loss of young fruit, so that more fruit abscission occurs. Thinning measures become more effective.