8 julio, 2024

Woody stems: what they are, characteristics, types and uses

What are woody stems?

The woody stems They are perennial plant support structures that develop hard tissues, commonly known as wood. These tissues are made up of fibers and vascular bundles with lignified cells that constitute the log or wood. This allows them to reach much higher measurements.

Plants that develop woody stems have a layer of meristematic cells called the cambium between the phloem and the xylem. The cambium represents the meristematic plant tissue responsible for the growth in thickness of the plant.

Plants with woody stems have a continuous growth phase where the weight and thickness of the trunk increase. This is because the main axis of the trees develops successive structural layers so that the plant can grow in size.

The function of the woody stem is to support the vascular bundles that transport water and nutrients from the roots to the leaves, as well as the sugars generated in the photosynthesis process from the leaves to the rest of the plant.

The woody tissue is renewed annually, promoting the growth in diameter of the trunk of the plant. The wood product of vegetative growth is deposited externally under the bark. In certain monocots, the heartwood or woody tissue accumulates inside the stem.

Characteristics of woody stems

The woody stem presents a secondary growth and is lignified, since it is made up of secondary xylem —wood or log—. Some examples of woody stems are the shrubby and treelike structures of gymnosperms and certain dicotyledonous angiosperms.
The trunk or shaft of a woody plant is constituted from the outside by the epidermis. On some occasions this epidermis presents an easy detachment due to the growth in thickness of the plant.
Next, the outermost secondary meristem appears, called the suberous or phellogenous cambium, and then the phelodermis. The phellogen is the secondary tissue that produces the suberous tissue that covers the plant towards the outside.
The phellodermis is formed from the phellogen, and constitutes, together with the suberous cells and the phellogen, the periderm. In fact, the periderm is a secondary protective tissue that replaces the epidermis in woody or secondary growth plants.
Next in this order is the parenchymatic tissue and the secondary phloem or sieve tissue, originated from the cambium. All these tissues constitute the bark of the plant, delimited by the vascular cambium whose function is the formation of secondary xylem and phloem.
Under the vascular cambium are the rings of xylem responsible for the growth in thickness of the plant. The number of xylem rings determines the age of the plant, since their formation occurs annually.
Under the bark is located the sapwood, active tissue or light-colored living wood, whose function is to conduct liquids from the roots to the foliage. The internal part of the trunk is made up of the duramen —heart of the wood—, a dark-colored tissue of dead cells.

Types of woody stems

The woody stems are classified, depending on the height, into trees, shrubs, and bushes or vines.

Trees

Trees are plants with a woody stem that have branches at a certain height from the ground. For a plant to be included in the category of trees, it must have a height greater than 5 meters at maturity.

In fact, trees annually develop new secondary branches that originate from the main trunk or stem. A minimum trunk diameter of 20-30 cm has been established to classify a plant as a tree.

In trees, the presence of a single main axis or trunk is evident, made up of a rough and thick bark. Some examples of trees are oak (Quercus robur), Pine tree (Pinus sp..), saman (samanea saman), carob (Ceratonia siliqua) or cedar (cedrus libani).

Shrubbery

Shrubs are medium-sized woody plants that branch out at ground level. Most shrubs have average heights between 1 and 5 meters.

Branches are usually more than one, growing at ground level or from a short main stem. Examples of shrubs are lavender (Lavandula angustifolia), hydrangea (Hydrangea sp..) and the moral (Morus nigra).

bushes or climbers

The bushes or climbers -vines- are those plants with woody stems that do not measure more than one meter in height. The short stem of some climbers presents a woody structure from which secondary branches develop.

Among the climbers we can mention the vine or vine (Vitis vinifera), the clematis (Clematis sp.) and honeysuckle (Lonicera sp.). Likewise, some low-growing aromatic plants have woody stems covered with a thin bark, such as rosemary (Rosmarinus officinalis).

Applications

Construction

Trees constitute a renewable natural resource under restricted conditions, since it depends on reforestation programs. The wood obtained from the woody stems is used mainly in the construction of furniture and houses.

Industry

Secondary products such as resin, latex and syrup are obtained from the wood. Sawdust is a waste byproduct of industrialization, and cork comes from the outer layer of some woody species.
The wood contains tannins that are used by the textile industry and leather tanning. In addition, it is used in the production of paper and as vegetable fuel.

Medicinal

The woody bark of various species is used for medicinal purposes for the prevention and treatment of multiple diseases. The bark of trees such as pine (Pinus sp.), the cedar (cedrela odorata), and the palo santo (Bursera graveolens) have healing properties.
The decoction of the pine bark is used to clean ulcers. The resin is used to relieve gout and rheumatism. The infusion or tea of ​​the bark and tender shoots relieves colds, bronchitis, colds and coughs, and also helps reduce fever.
Cedar bark is used as an astringent, antirheumatic, balsamic, bronchitic and diuretic. The cedar can be used as an infusion or tea, bark cooking baths, or as a poultice of leaves and bark.
Palo santo contains the antioxidant limonene in its bark, which is used to dissolve kidney and urinary tract stones. It is also a preventive element of cancer, mammary tumors and pancreas. Wood ash is used to soothe external wounds.

References

Raven, PH, Evert, RF & Eichhorn, SE Plant Biology.
Fence, JJ Botany. Morphology of superior plants. Editorial Southern Hemisphere.

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