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Apical dominance GudangMovies21 Rebahinxxi LK21
In botany, apical dominance is the phenomenon whereby the main, central stem of the plant is dominant over (i.e., grows more strongly than) other side stems; on a branch the main stem of the branch is further dominant over its own side twigs.
Plant physiology describes apical dominance as the control exerted by the terminal bud (and shoot apex) over the outgrowth of lateral buds.
Overview
Apical dominance occurs when the shoot apex inhibits the growth of lateral buds so that the plant may grow vertically. It is important for the plant to devote energy to growing upward so that it can get more light to undergo photosynthesis. If the plant utilizes available energy for growing upward, it may be able to outcompete other individuals in the vicinity. Plants that were capable of outcompeting neighboring plants likely had higher fitness. Apical dominance is therefore most likely adaptive.
Typically, the end of a shoot contains an apical bud, which is the location where shoot growth occurs. The apical bud produces a plant hormone, auxin (IAA), that inhibits growth of the lateral buds further down on the stem towards the axillary bud. Auxin is predominantly produced in the growing shoot apex and is transported throughout the plant via the phloem and diffuses into lateral buds which prevents elongation. That auxin likely regulates apical dominance was first discovered in 1934.
When the apical bud is removed, the lowered IAA concentration allows the lateral buds to grow and produce new shoots, which compete to become the lead growth.
Apex removal
Plant physiologists have identified four different stages the plant goes through after the apex is removed (Stages I-IV). The four stages are referred to as
lateral bud formation,
"imposition of inhibition" (apical dominance),
initiation of lateral bud outgrowth following decapitation, and
elongation and development of the lateral bud into a branch.
These stages can also be defined by the hormones that are regulating the process which are as follows: Stage I, cytokinin promoted, causing the lateral bud to form since cytokinin plays a role in cell division; Stage II, auxin is promoted, resulting in apical dominance ("imposition of inhibition"); Stage III, cytokinin released resulting in outward growth of the lateral bud; and Stage IV, auxin is decreased and gibberellic acid is promoted which results in cell division, enabling the bud or branch to continue outward growth.
More simply stated, lateral bud formation is inhibited by the shoot apical meristem (SAM). The lateral bud primordium (from which the lateral bud develops) is located below SAM. The shoot tip rising from the SAM inhibits the growth of the lateral bud by repressing auxin. When the shoot is cut off, the lateral bud begins to lengthen which is mediated by a release of cytokinin. Once the apical dominance has been lifted from the plant, elongation and lateral growth is promoted and the lateral buds grow into new branches. When lateral bud formation prevents the plant from growing upward, it is undergoing lateral dominance. Often, lateral dominance can be triggered by decapitating the SAM or artificially decreasing the concentration of auxin in plant tissues.
Applications
When the apical bud is removed, the lowered IAA concentration allows the lateral buds to grow and produce new shoots, which compete to become the lead growth. Pruning techniques such as coppicing and pollarding make use of this natural response to curtail direct plant growth and produce a desired shape, size, and/or productivity level for the plant. The principle of apical dominance is manipulated for espalier creation, hedge building, or artistic sculptures called topiary. If the SAM is removed, it stimulates growth in the lateral direction. By careful pruning, it is possible to create remarkable designs or patterns.
Some fruit trees have strong apical dominance, and young trees can become "leggy", with poor side limb development. Apical dominance can be reduced in this case, or in cases where limbs are broken off by accident, by cutting off the auxin flow above side buds that one wishes to stimulate. This is often done by orchardists for young trees.
Occasionally, strong apical dominance is advantageous, as in the "Ballerina" apple trees. These trees are intended to be grown in small gardens, and their strong apical dominance combined with a dwarfing rootstock gives a compact narrow tree with very short fruiting side branches.
See also
Meristem
Fruit tree pruning
References
Thimann, Kenneth V.; Skoog, Folke (1933). "Studies on the growth hormone of plants: III. The inhibiting action of the growth hormone on bud development". Proceedings of the National Academy of Sciences of the United States of America. 19 (7): 714–716. doi:10.1073/pnas.19.7.714. PMC 1086139. PMID 16577553.
Dun, Elizabeth Ann; Ferguson, Brett James; Beveridge, Christine Anne (2006). "Apical Dominance and Shoot Branching. Divergent Opinions or Divergent Mechanisms?". Plant Physiology. 142 (3): 812–819. doi:10.1104/pp.106.086868. PMC 1630731. PMID 17093134.
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Apical Dominance - THCFarmer
May 1, 2011 · Apical Dominance a condition where vertical growth supercedes lateral growth in a plant. this is controlled by auxins, where in high concentrations can inhibit growth but on the whole promote it. Removal of the apex can induce lateral growth. Typically a shoot has leaves attached to a stem. The apex of the stem has an actively growing apical bud.
High Science : Apical Dominance - but wait, there’s more
Nov 18, 2020 · Three theories for apical dominance have existed since the 1930s, Direct, Diversion and Indirect. Over eight decades, the first two theories have been heavily studied and were adapted to Auxin Transport Canalization and Second Messenger theories, respectively. However, neither can fully explain the phenomenon of apical dominance.
Do i trim of the leaves in the bottom or i let them be ... - THCFarmer
Jan 14, 2025 · You can just let them grow and in preflower take the main stem and pull it softly to 90° down, doing that promote the lower shoots due to breaking the apical dominance, which also happen with topping, just with less stress.
High Times at Redneck'x Cabin - THCFarmer
Nov 26, 2024 · With breaking the apical dominance I should archive to get a wider and not so tall plants right? Is there a point when the dominance fell apart and shoots in the sky like there is no limit? Maybe during flip?View attachment 2330082
Super Lemon Haze manifold 12:12 from seed - THCFarmer
Mar 10, 2023 · The manifold method outdoor seems to have produced more useful buds and kept the plant at much more managable height. The only training was getting the two stems to grow somewhat sideways after the first pruning, but apical dominance is still severly restricted.
Conditioning, Configuring, Dialing, And Refreshing Blumat
Aug 22, 2017 · How they work Blumat operates off of capillary pressure. This is why they must be conditioned. Its basically the pressure created by the soil trying to wick the water from the carrot. when it does this it slowly opens a valve located on the top of the carrot.
Oct 22, 2019 · Yes, this product helps with roots, but what people do not understand is that this form of kelp tends to contain higher Cytokinin counts than Auxin Counts. These two things are considered natural growth hormones where Cytokinins regulate axillary bud growth, apical dominance and shoot growth.
Duds; Is It A Virus? - THCFarmer
Dec 20, 2015 · Lack of apical dominance. Plants sometime grow wider than tall. No normal large fan leaf growth. Leaves are generally small and blades tend to point upward with an overall “spiky” appearance. The plants have an unusual branch structure, sometimes referred to as “witch-brooming.” Branches often bow down instead of growing up at a steep ...
When Do I Untie Branches During Flower? - THCFarmer
Mar 10, 2019 · There's a blooming hormone in the plant that kinda builds up more in the highest branches or if it's untopped the main cola.the more the branch stays at the top the more the blooming hormone builds up in that branch the more effort/energy =bud it puts on that branch to the detriment of the lower branches.what you want to do,even if the branches are thicker or …
When To Use Pk 13/14....?? - THCFarmer
Apr 21, 2017 · Yes..but phosphorus is the real culprit with early flower stretch. Tissue analysis proves it. Nitrogen makes for bendy flexy apical dominance. Lack of sugary carbs. Energy spending. And nitrates are different. Ammonium nitrate is a whole different game.
