Apical dominance

In plant physiology, 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 branchlets.

The apical bud (or tip) produces the growth hormone auxin, which not only promotes cell division, but also diffuses downwards and inhibits the development of lateral bud growth which would otherwise compete with the apical tip for light and nutrients. Removing the apical tip and its suppressive hormone, allows the lower dormant lateral buds to develop, and the buds between the leaf stalk and stem produce new shoots which compete to become the lead growth. Manipulating this natural response to damage (known as the principle of apical dominance) by processes such as pruning (as well as coppicing and pollarding) allows the horticulturist to determine the shape, size and productivity of many fruiting trees and bushes.

Understanding the principle of apical dominance is helpful when embarking upon any regime of tree or other plant management. Plants form new tissue in an area called the meristem, located near the tips of roots and shoots, where active cell division takes place. Meristem growth is aimed at ensuring that leaves are quickly elevated into sunlight, and that roots are able to penetrate deeply into the soil. Once adequate height and length is achieved by the stems and roots, they will begin to thicken to give support to the plant. On the shoots, these growing tips of the plant are known as apical buds.

Some fruit trees have strong apical dominance, and young trees can become "leggy", with poor side limb development. One can reduce the apical dominance 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. Select the bud along the leader (stem) where one desires a side branch to develop, or where one already is present, but growing too weakly. With a sharp knife make a horizontal cut about a half inch above it, just deep enough to break the cambium, and only about a quarter of the way around the stem. This breaks the flow of auxins that had suppressed its growth. Later, when a bud breaks, it can be trained or pruned as needed.

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 Fruit trees pruning

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  • apical dominance — viršūnės vyravimas statusas T sritis augalininkystė apibrėžtis Vyravimo atvejis, kuriam reiškiantis viršūnė stelbia šoninių pumpurų augimą. atitikmenys: angl. apical dominance rus. апикальное доминирование; доминирование верхушки ryšiai:… …   Žemės ūkio augalų selekcijos ir sėklininkystės terminų žodynas

  • apical dominance —   Dominance of the apical growing shoot which produces hormones and prevents offset or suckers from developing while it is still actively growing …   Expanded glossary of Cycad terms

  • apical dominance — Growth inhibiting effect exerted by actively growing apical bud of higher plant shoots, preventing the growth of buds further down the shoot. Thought to be mediated by the basipetal movement of auxin from the apical bud …   Dictionary of molecular biology

  • apical dominance — The phenomenon where growth of lateral (axillary) buds in a plant is inhibited by the presence of the terminal (apical) bud on the branch. Explained by the export of auxins from the apical bud …   Glossary of Biotechnology

  • apical dominance — noun Date: 1947 inhibition of the growth of lateral buds by the terminal bud of a shoot …   New Collegiate Dictionary

  • apical dominance — Bot. suppression of the development of lateral buds in a growing plant shoot, caused by hormones produced in the tip of the shoot. [1945 50] * * * …   Universalium

  • apical dominance — noun : inhibition of the growth of lateral buds by the terminal bud of a shoot that is believed to be effected principally or at least in part by auxins produced by the terminal bud * * * Bot. suppression of the development of lateral buds in a… …   Useful english dictionary

  • Apical — Apical, from the Latin apex (plural apices ) meaning to be at the apex or tip, may refer to:*Apical consonant, a consonant produced with the tip of the tongue *Apical dominance *Apical membrane, a cell biology term *Apical pulse, the heart rate… …   Wikipedia

  • apicaldominance — apical dominance n. Inhibition of the growth of lateral buds by the terminal bud of a plant shoot. * * * …   Universalium

  • Meristem — Tunica Corpus model of the apical meristem (growing tip). The epidermal (L1) and subepidermal (L2) layers form the outer layers called the tunica. The inner L3 layer is called the corpus. Cells in the L1 and L2 layers divide in a sideways fashion …   Wikipedia

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