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A woody plant is a
plant
plant
that produces
wood
wood
as its structural tissue and thus has a hard stem. In cold climates, woody plants further survive
winter
winter
or
dry season The dry season is a yearly period of low rainfall, especially in the tropics The tropics are the region of Earth surrounding the Equator. They are delimited in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropi ...
above ground, as opposite to
herbaceous Herbaceous plants are vascular plant Vascular plants (from Latin ''vasculum'': duct), also known as Tracheophyta (the tracheophytes , from the Greek ''trācheia''), form a large group of plants ( 300,000 accepted known species) that are defined ...
plants that die back to the ground until
spring Spring(s) may refer to: Common uses * Spring (season), a season of the year * Spring (device), a mechanical device that stores energy * Spring (hydrology), a natural source of water * Spring (mathematics), a geometric surface in the shape of a heli ...
.


Characteristics

Woody plants are usually either
tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, supporting branches and leaves in most species. In some usages, the definition of a tree may be narrower, including only wood plants with se ...

tree
s,
shrub A shrub (often called a bush) is a small- to medium-sized perennial A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate ...

shrub
s, or
liana A liana is a long-Plant stem, stemmed, Woody plant, woody vine that is rooted in the soil at ground level and uses trees, as well as other means of vertical support, to climb up to the Canopy (biology), canopy in search of direct sunlight. Li ...

liana
s. These are usually
perennial plant A perennial plant or simply perennial is a plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and incl ...
s whose stems and larger roots are reinforced with wood produced from secondary
xylem Xylem is one of the two types of transport tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North Amer ...

xylem
. The main stem, larger branches, and roots of these plants are usually covered by a layer of
bark Bark may refer to: * Bark (botany), an outer layer of a woody plant * Bark (sound), a vocalization of some animals Places * Bark, Germany * Bark, Warmian-Masurian Voivodeship, Poland Arts, entertainment, and media * ''Bark'' (Jefferson Airp ...
. Wood is a structural
tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ''Triphosa dubitata'', a species of geometer mot ...
that allows woody plants to grow from above ground stems year after year, thus making some woody plants the largest and tallest
terrestrial plant A terrestrial plant is a plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; ho ...
s. Woody plants, like herbaceous perennials, typically have a dormant period of the year when growth does not take place, in colder climates due to freezing temperatures and lack of daylight during the winter months, in subtropical and tropical climates due to the dry season when precipitation becomes minimal. The dormant period will be accompanied by shedding of leaves if the plant is deciduous. Evergreen plants do not lose all their leaves at once (they instead shed them gradually over the growing season), however growth virtually halts during the dormant season. Many woody plants native to subtropical regions and nearly all native to the tropics are evergreen due to year-round warm temperatures. During the fall months, each stem in a deciduous plant cuts off the flow of nutrients and water to the leaves. This causes them to change colors as the chlorophyll in the leaves breaks down. Special cells are formed that sever the connection between the leaf and stem, so that it will easily detach. Evergreen plants do not shed their leaves and merely go into a state of low activity during the dormant season. During spring, the roots begin sending nutrients back up to the canopy. When the growing season resumes, either with warm weather or the wet season, the plant will break bud by sending out new leaf or flower growth. This is accompanied by growth of new stems from buds on the previous season's wood. In colder climates, most stem growth occurs during spring and early summer. When the dormant season begins, the new growth hardens off and becomes woody. Once this happens, the stem will never grow in length again, however it will keep expanding in diameter for the rest of the plant's life. Most woody plants native to colder climates have distinct
growth ring Dendrochronology (or tree-ring dating) is the scientific method The scientific method is an Empirical evidence, empirical method of acquiring knowledge that has characterized the development of science since at least the 17th century. It in ...
s produced by each year's production of new vascular tissue. Only the outer handful of rings contain living tissue (the
cambium A cambium (plural cambia or cambiums), in plants, is a tissue layer that provides partially undifferentiated cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic ...
,
xylem Xylem is one of the two types of transport tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North Amer ...

xylem
,
phloem Phloem (, ) is the living biological tissue, tissue in vascular plants that transports the soluble Organic chemistry, organic Chemical substance, compounds made during photosynthesis and known as ''photosynthates'', in particular the sugar sucrose ...

phloem
, and sapwood). Inner layers have heartwood, dead tissue that serves merely as structural support.


Growth

Stem growth primarily occurs out of the terminal bud on the tip of the stem. Buds on the sides of the stem are suppressed by the terminal bud and produce less growth, unless it is removed by human or natural action. Without a terminal bud, the side buds will have nothing to suppress them and begin rapidly sending out growth, if cut during spring. By late summer and early autumn, most active growth for the season has ceased and pruning a stem will result in little or no new growth. Winter buds are formed when the dormant season begins. Depending on the plant, these buds contain either new leaf growth, new flowers, or both. Terminal buds have a stronger dominance on conifers than broadleaf plants, thus conifers will normally grow a single straight trunk without forking or large side or lateral branches. As a woody plant grows, it will often lose lower leaves and branches as they become shaded out by the canopy. If a given stem is producing an insufficient amount of energy for the plant, the roots will "abort" it by cutting off the flow of water and nutrients, causing it to gradually die. Below ground, the root system expands each growing season in much the same manner as the stems. The roots grow in length and send out smaller lateral roots. At the end of the growing season, the newly grown roots become woody and cease future length expansion, but will continue to expand in diameter. However, unlike the above-ground portion of the plant, the root system continues to grow, although at a slower rate, throughout the dormant season. In cold-weather climates, root growth will continue as long as temperatures are above 36 °F (2 °C).


Tissue composition

Wood is primarily composed of xylem cells with
cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane cell membrane vs. Prokaryotes The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to a ...
s made of
cellulose Cellulose is an organic compound , CH4; is among the simplest organic compounds. In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ...
and
lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood Wood is a porous and fibrous s ...

lignin
. Xylem is a
vascular tissue stalk, showing vascular bundles, which include both phloem and xylem. Image:BrambleLeaf_CrossPolarisedLight_Diagram.jpg, 250px, Detail of the vasculature of a bramble leaf. Vascular tissue is a complex conducting tissue (biology), tissue, formed ...
which moves water and nutrients from the roots to the leaves. Most woody plants form new layers of woody tissue each year, and so increase their stem diameter from year to year, with new wood deposited on the inner side of a
vascular cambium The vascular cambium is the main growth tissue in the stems and roots of many plants, specifically in dicots such as buttercups and oak trees, gymnosperm The gymnosperms, also known as Acrogymnospermae, are a group of seed-producing plants th ...
layer located immediately beneath the bark. However, in some
monocotyledons Monocotyledons (), commonly referred to as monocots, ( Lilianae '' sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds A seed is an Plant embryogenesis, embryonic plant enclosed in a testa (botany), pr ...
such as palms and dracaenas, the wood is formed in bundles scattered through the interior of the trunk. Stem diameter increases continuously throughout the growing season and halts during the dormant period. Under specific conditions, woody plants may decay or may in time become
petrified wood File:PetrifiedWood.jpg, Petrified log at the Petrified Forest National Park Petrified wood (from Ancient Greek meaning 'rock' or 'stone'; literally 'wood turned into stone') is the name given to a special type of fossilized remains of terrestr ...

petrified wood
.


Symbol

The symbol for a woody plant, based on ''
Species Plantarum ' (Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republic, i ...
'' by
Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his Nobility#Ennoblement, ennoblement as Carl von Linné#Blunt, Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomia ...
is , which is also the
astronomical symbol Astronomical symbols are abstract pictorial symbols used to represent astronomical objects, theoretical constructs and observational events in Western culture, European astronomy. The earliest forms of these symbols appear in Greek papyrus text ...
for the planet
Saturn Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It only has one-eighth the average density of Earth; how ...

Saturn
.


See also

*
Arboriculture An arborist practicing tree care: using a chainsaw">tree_care.html" ;"title="arborist practicing tree care">arborist practicing tree care: using a chainsaw to fell a eucalyptus tree in a park at Kallista, Victoria. Arboriculture () is the cultivati ...
*
Dendrology Dendrology ( grc, δένδρον, ''dendron'', "tree"; and grc, -λογία, '' -logia'', ''science of'' or ''study of'') or xylology ( grc, ξύλον, ''ksulon'', "wood") is the science and study of wooded plants (tree In botany, a tr ...
*
Inosculation Inosculation is a natural phenomenon in which trunks, branches or roots of two tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, supporting branches and leaves in most species. In som ...
*
Vascular plant Vascular plants (from Latin ''vasculum'': duct), also known as Tracheophyta (the tracheophytes , from Greek τραχεῖα ἀρτηρία ''trācheia artēria'' 'windpipe' + φυτά ''phutá'' 'plants'), form a large group of plants ( 300,000 a ...


References

{{Authority control Plants
Plant morphology ''Plant morphology'' is the field in botany that studies the diversity in forms, with the naked eye or slight optical magnification. This is opposed to plant anatomy (see :Plant anatomy) that needs to cut into plants to be able to study its subject, ...
Dendrology Biology terminology