Woody plant

A woody plant is a plant that produces wood as its structural tissue. Woody plants are usually either trees, shrubs, or lianas. These are usually perennial plants whose stems and larger roots are reinforced with wood produced from secondary xylem. The main stem, larger branches, and roots of these plants are usually covered by a layer of bark. Wood is a structural cellular adaptation that allows woody plants to grow from above ground stems year after year, thus making some woody plants the largest and tallest terrestrial plants.

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 rings produced by each year's production of new vascular tissue. Only the outer handful of rings contain living tissue (the cambium, xylem, pholem, and sapwood). Inner layers have heartwood, dead tissue that serves merely as structural support.

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).

Wood is primarily composed of xylem cells with cell walls made of cellulose and lignin. Xylem is a vascular tissue 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 layer located immediately beneath the bark. However, in some monocotyledons 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.[1]

Under specific conditions, woody plants may decay or may in time become petrified wood.

The symbol for a woody plant, based on Species Plantarum by Linnaeus is ♃, which is also the astronomical symbol for the planet Saturn.[2]

RosmaryStem SatCrop BgSub
A section of rosemary stem, an example of a woody plant, showing a typical wood structure.

See also

References

  1. ^ Chase, Mark W. (2004). "Monocot relationships: an overview". Am. J. Bot. 91 (10): 1645–1655. doi:10.3732/ajb.91.10.1645. PMID 21652314.
  2. ^ Stearn, William T. (1992) [1966]. Botanical Latin (Fourth ed.). Portland: Timber Press. ISBN 0881923214.
Aralia elata

Aralia elata, commonly called Chinese angelica-tree, Japanese angelica-tree, and Korean angelica-tree, is a woody plant belonging to the family Araliaceae. It is known as tara-no-ki (タラノキ; 楤木) in Japanese, and dureup-namu (두릅나무) in Korean.

Crown (botany)

The crown of a plant refers to the totality of an individual plant's aboveground parts, including stems, leaves, and reproductive structures. A plant community canopy consists of one or more plant crowns growing in a given area.

The crown of a woody plant (tree, shrub, liana) is the branches, leaves, and reproductive structures extending from the trunk or main stems.

Shapes of crowns are highly variable. The major types for trees are the excurrent branching habit resulting in conoid shapes and decurrent (deliquescent) branching habit, resulting in round shapes. Crowns are also characterized by their width, depth, surface area, volume, and density. Measurements of crowns are important in quantifying and qualifying plant health, growth stage, and efficiency.

Major functions of the crown include light energy assimilation, carbon dioxide absorption and release of oxygen via photosynthesis, energy release by respiration, and movement of water to the atmosphere by transpiration. These functions are performed by the leaves.

Eastern Asiatic Region

The Eastern Asiatic Region (also known as Oriasiaticum, Sino-Japanese Region, East Asian Region, Temperate Eastern Region) is the richest floristic region within the Holarctic Kingdom and situated in temperate East Asia. It has been recognized as a natural floristic area since 1872 August Grisebach's volume Die Vegetation der Erde and later delineated by such geobotanists as Ludwig Diels, Adolf Engler (as Temperate Eastern region), Ronald Good (as Sino-Japanese Region) and Armen Takhtajan.

The Eastern Asiatic Region is dominated by very old lineages of gymnosperms and woody plant families and is thought to be the cradle of the Holarctic flora. Moreover, this floristic region wasn't significantly glaciated in the Pleistocene, and many relict Tertiary genera (such as Metasequoia glyptostroboides, ancestors of which were once common throughout the Northern Hemisphere up to subpolar latitudes) found refuge here.

Fagaceae

Fagaceae is a family of flowering plants that includes beeches and oaks, and comprises eight genera with about 927 species. The Fagaceae are deciduous or evergreen trees and shrubs, characterized by alternate simple leaves with pinnate venation, unisexual flowers in the form of catkins, and fruit in the form of cup-like (cupule) nuts. Their leaves are often lobed and both petioles and stipules are generally present. Leaf characteristics of Fagaceae can be very similar to those of Rosaceae and other rose motif families. Their fruits lack endosperm and lie in a scaly or spiny husk that may or may not enclose the entire nut, which may consist of one to seven seeds. In the oaks, genus Quercus, the fruit is a non-valved nut (usually containing one seed) called an acorn. The husk of the acorn in most oaks only forms a cup in which the nut sits. Other members of the family have fully enclosed nuts. Fagaceae is one of the most ecologically important woody plant families in the Northern Hemisphere, as oaks form the backbone of temperate forest in North America, Europe, and Asia and one of the most significant sources of wildlife fodder.

Several members of the Fagaceae have important economic uses. Many species of oak, chestnut, and beech (genera Quercus, Castanea, and Fagus, respectively) are commonly used as timber for floors, furniture, cabinets, and wine barrels. Cork for stopping wine bottles and myriad other uses is made from the bark of cork oak, Quercus suber. Chestnuts are the fruits from species of the genus Castanea. Numerous species from several genera are prominent ornamentals, and wood chips from the genus Fagus are often used in flavoring beers.

Ficus retusa

Ficus retusa is a species of evergreen woody plant in the fig genus, native to the Malay Archipelago and Malesia floristic region. The species name has been widely mis-applied to Ficus microcarpa.

Juniperus communis

Juniperus communis, the common juniper, is a species of conifer in the genus Juniperus, in the family Cupressaceae. It has the largest geographical range of any woody plant, with a circumpolar distribution throughout the cool temperate Northern Hemisphere from the Arctic south in mountains to around 30°N latitude in North America, Europe and Asia. Relict populations can be found in the Atlas Mountains of Africa.

Juniperus indica

Juniperus indica, the black juniper, is a juniper native to high-altitude climates in the Himalaya, occurring from the northern Indus Valley in Kashmir east to western Yunnan in China.

It is of interest as the highest elevation woody plant known, reported growing as high as 5200 m in southern Tibet; the lowest limit being 2600 m.

It is a shrub growing to 50–200 cm tall, with largely horizontal branching. The leaves are dark grey-green, dimorphic, with adult plants having mostly scale-like leaves 1–3 mm long, while young plants have mostly needle-like leaves 5–8 mm long, but needle-like leaves can also be found on shaded shoots of adult plants. The leaves are borne in whorls of three on strong stout main stem shoots, and opposite pairs on thinner, slower-growing shoots. It is dioecious, with male (pollen) and female (seed) cones on separate plants. The mature seed cones are ovoid, berry-like, 6–10 mm long, glossy black, and contain a single seed; the seeds are dispersed by birds which eat the cones, digest the fleshy cone pulp, and excrete the seeds in their droppings.

Lecythis

Lecythis is a genus of woody plant in the Lecythidaceae family first described as a genus in 1758. It is native to Central America and South America.

Marsh

A marsh is a wetland that is dominated by herbaceous rather than woody plant species. Marshes can often be found at the edges of lakes and streams, where they form a transition between the aquatic and terrestrial ecosystems. They are often dominated by grasses, rushes or reeds. If woody plants are present they tend to be low-growing shrubs. This form of vegetation is what differentiates marshes from other types of wetland such as swamps, which are dominated by trees, and mires, which are wetlands that have accumulated deposits of acidic peat.

Oasification

In hydrology, oasification is the antonym to desertification by soil erosion; this technique has limited application and is normally considered for much smaller areas than those threatened by desertification.

To help the oasification process, engineers aim to develop a thriving dense woody plant cover to redress the hydrological, edaphic and botanical degradation affecting a slope. This is done through appropriate soil preparation and the introduction of suitable plant species. It is also necessary to make adequate water harvesting systems—ideally taking advantage of the degradation process of the slope, collecting runoff water in ponds around the sites to be forested.

The term "oasification" was coined in 1999 by Andrés Martínez de Azagra Paredes, PhD Forest Engineer and professor on Hydraulics and Forest Hydrology at E.T.S. of Agroforestry Engineering in Palencia, University of Valladolid, Spain.

In oasification, soil and nutrient harvesting are regarded as fundamental component parts in the reclamation process of a degraded slope. Besides harvesting water, oasification preserves and accumulates soil and nutrients, helping to control water erosion—a common problem in dry climates. Ludwig et al. (1997) reported about sloping areas under semiarid conditions in Australia where the landscape is naturally divided into source and sink zones (surface runoff and run-on areas), which are sometimes reclaimed by plant species through retention of water soil and litter.

Picloram

Picloram is a systemic herbicide used for general woody plant control. It also controls a wide range of broad-leaved weeds, but most grasses are resistant. A chlorinated derivative of picolinic acid, picloram is in the pyridine family of herbicides.

Picloram can be sprayed on foliage, injected into plants, applied to cut surfaces, or placed at the base of the plant where it will leach to the roots. Once absorbed by the foliage, stem, or roots, picloram is transported throughout the plant.

Herbicides containing Picloram are sold under a variety of brand names. Dow Chemicals and now Dow AgroSciences sell herbicides containing it under the brand name Tordon.During the Vietnam War, a mixture of picloram and other herbicides were combined to make Agent White (commercially available as Tordon 101) and enhanced Agent Orange which was previously conducted by the British military during the Malayan Emergency. Large quantities of these herbicides were sprayed by U.S. forces in areas where they considered its long-term persistence desirable, such as inland forests.

Prostrate shrub

A prostrate shrub is a woody plant, most of the branches of which lie upon or just above the ground, rather than being held erect as are the branches of most trees and shrubs.

Pruning

Pruning is a horticultural and silvicultural practice involving the selective removal of certain parts of a plant, such as branches, buds, or roots. Reasons to prune plants include deadwood removal, shaping (by controlling or redirecting growth), improving or sustaining health, reducing risk from falling branches, preparing nursery specimens for transplanting, and both harvesting and increasing the yield or quality of flowers and fruits.

The practice entails targeted removal of diseased, damaged, dead, non-productive, structurally unsound, or otherwise unwanted tissue from crop and landscape plants. In general, the smaller the branch that is cut, the easier it is for a woody plant to compartmentalize the wound and thus limit the potential for pathogen intrusion and decay. It is therefore preferable to make any necessary formative structural pruning cuts to young plants, rather than removing large, poorly placed branches from mature plants.

Specialized pruning practices may be applied to certain plants, such as roses, fruit trees, and grapevines. It is important when pruning that the tree’s limbs are kept intact, as this is what helps the tree stay upright. Different pruning techniques may be deployed on herbaceous plants than those used on perennial woody plants. Hedges, by design, are usually (but not exclusively) maintained by hedge trimming, rather than by pruning.

In nature, meteorological conditions such as wind, ice and snow, and salinity can cause plants to self-prune. This natural shedding is called abscission.

Savanna

A savanna or savannah is a mixed woodland grassland ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of grasses.Savannas maintain an open canopy despite a high tree density. It is often believed that savannas feature widely spaced, scattered trees. However, in many savannas, tree densities are higher and trees are more regularly spaced than in forests. The South American savanna types cerrado sensu stricto and cerrado dense typically have densities of trees similar to or higher than that found in South American tropical forests, with savanna ranging from 800–3300 trees per hectare (trees/ha) and adjacent forests with 800–2000 trees/ha. Similarly Guinean savanna has 129 trees/ha, compared to 103 for riparian forest, while Eastern Australian sclerophyll forests have average tree densities of approximately 100 per hectare, comparable to savannas in the same region.Savannas are also characterised by seasonal water availability, with the majority of rainfall confined to one season; they are associated with several types of biomes, and are frequently in a transitional zone between forest and desert or grassland. Savanna covers approximately 20% of the Earth's land area.

Shrub

A shrub or bush is a small- to medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. They are distinguished from trees by their multiple stems and shorter height, less than 6 m-10 m (20 ft–33 ft) tall. Small shrubs, less than 2 m (6.6 ft) tall are sometimes termed subshrubs.

Subshrub

A subshrub (Latin suffrutex) or dwarf shrub is a short woody plant. Prostrate shrub is a related term. "Subshrub" is often used interchangeably with "bush".Because the criteria are matters of degree rather than of kind, the definition of a subshrub is not sharply distinguishable from that of a shrub; examples of reasons for describing plants as subshrubs include ground-hugging stems or low growth habit. Subshrubs may be largely herbaceous, with overwintering perennial woody growth much lower-growing than deciduous summer growth. Some plants described as subshrubs are only weakly woody and some persist for only for a few years; others however, such as Oldenburgia paradoxa live indefinitely, rooted in rocky cracks.

Small, low shrubs such as lavender, periwinkle, and thyme, and many members of the family Ericaceae, such as cranberries and small species of Erica, are often classed as subshrubs.

Witch's broom

Witch's broom or witches' broom is a deformity in a woody plant, typically a tree, where the natural structure of the plant is changed. A dense mass of shoots grows from a single point, with the resulting structure resembling a broom or a bird's nest. It is sometimes caused by pathogens.

Witch-broom disease caused by phytoplasmas is economically important in a number of crop plants, including the cocoa tree Theobroma cacao,jujube (Ziziphus jujuba) and the timber tree Melia azedarach.

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