In
plant physiologyPlant physiology is a subdiscipline of botany concerned with the functioning, or physiology, of plants. Closely related fields include plant morphology , plant ecology , phytochemistry , cell biology, and molecular biology.Fundamental processes such as photosynthesis, respiration, plant nutrition,...
,
apical dominance is the phenomenon whereby the main central
stemA stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , cones or other stems etc. The internodes act as spaces that distance one node from another...
of the
plantPlants are living organisms belonging to the kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The scientific study of plants, known as botany, has identified about 350,000 extant species of plants, defined as seed plants,...
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
hormoneA hormone is a chemical released by one or more cells that affects cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. It is essentially a chemical messenger that transports a signal from one cell to another. All multicellular organisms...
auxinAuxins are a class of plant growth substance and morphogens . Auxins have an essential role in coordination of many growth and behavioral processes in the plant life cycle...
, which not only promotes
cell divisionCell division is a process by which a cell, called the parent cell, divides into two or more cells, called daughter cells. Cell division is usually a small segment of a larger cell cycle. This type of cell division in eukaryotes is known as mitosis, and leaves the daughter cell capable of dividing...
, but also diffuses downwards and inhibits the development of lateral
budthumb|right|Flower buds have not yet bloomed into a full-size flower.In botany, a bud is an undeveloped or embryonic shoot and normally occurs in the axil of a leaf or at the tip of the stem...
growth which would otherwise compete with the apical tip for light and nutrients.
In
plant physiologyPlant physiology is a subdiscipline of botany concerned with the functioning, or physiology, of plants. Closely related fields include plant morphology , plant ecology , phytochemistry , cell biology, and molecular biology.Fundamental processes such as photosynthesis, respiration, plant nutrition,...
,
apical dominance is the phenomenon whereby the main central
stemA stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , cones or other stems etc. The internodes act as spaces that distance one node from another...
of the
plantPlants are living organisms belonging to the kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The scientific study of plants, known as botany, has identified about 350,000 extant species of plants, defined as seed plants,...
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
hormoneA hormone is a chemical released by one or more cells that affects cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. It is essentially a chemical messenger that transports a signal from one cell to another. All multicellular organisms...
auxinAuxins are a class of plant growth substance and morphogens . Auxins have an essential role in coordination of many growth and behavioral processes in the plant life cycle...
, which not only promotes
cell divisionCell division is a process by which a cell, called the parent cell, divides into two or more cells, called daughter cells. Cell division is usually a small segment of a larger cell cycle. This type of cell division in eukaryotes is known as mitosis, and leaves the daughter cell capable of dividing...
, but also diffuses downwards and inhibits the development of lateral
budthumb|right|Flower buds have not yet bloomed into a full-size flower.In botany, a bud is an undeveloped or embryonic shoot and normally occurs in the axil of a leaf or at the tip of the stem...
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 to 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
coppicingCoppicing is a traditional method of woodland management in which young tree stems are repeatedly cut down to near ground level. In subsequent growth years, many new shoots will emerge, and, after a number of years the coppiced tree, or stool, is ready to be harvested, and the cycle begins again...
and
pollardingPollarding is a pruning system in which the tree is headed back every year. This pruning encourages lateral branches and is normally done two or three metres above ground level. The tree is allowed to regrow after the initial cutting, but once begun, pollarding requires regular maintenance by...
) 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
treeA tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
or other plant management. Plants form new tissue in an area called the
meristemA meristem is the tissue in all plants consisting of undifferentiated cells and found in zones of the plant where growth can take place....
, located near the tips of roots and shoots, where active cell division takes place.
MeristemA meristem is the tissue in all plants consisting of undifferentiated cells and found in zones of the plant where growth can take place....
growth is aimed at ensuring that leaves are quickly elevated into sunlight, and that roots are able to penetrate deeply into the
soilSoil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics. It is composed of particles of broken rock that have been altered by chemical and...
. 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 budA meristem is the tissue in all plants consisting of undifferentiated cells and found in zones of the plant where growth can take place....
s.
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
cambiumIn botany this is a layer or layers of tissue, also known as lateral meristems, that are the source of cells for secondary growth. There are two types of cambium*Cork cambium*Vascular cambium-References:...
, 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"
appleThe apple is the pomaceous fruit of the apple tree, species Malus domestica in the rose family Rosaceae. It is one of the most widely cultivated tree fruits...
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.