WOODY STEMS: CHARACTERISTICS, TYPES AND USES - BIOLOGY - 2025

The woody stems are vegetables support structures that develop hardened tissue commonly known as wood. These tissues are made up of fibers and vascular bundles with lignified cells that make up the log or wood.

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

Woody stems. Source: pizabay.com

Plants with woody stems have a continuous growth phase where the weight and thickness of the trunk increases. 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 the vegetative growth is deposited externally under the bark. In certain monocots, the heartwood or woody tissue accumulates inside the stem.

General characteristics

The woody stem presents a secondary growth and is lignified, since it is constituted by secondary xylem -wood or log-. Some examples of woody stems are the shrub and tree structures of gymnosperms and certain dicot angiosperms.

The trunk or stem 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.

This is followed by the outermost secondary meristem called cambium suberoso or phellogen, followed by the felodermis. The phellogen is the secondary tissue that produces the suberose tissue that covers the plant outwards.

Cut of spruce tree (Picea) of the Pinaceae family. Source: pixabay.com

The felodermis is formed from the felogen, and together with the suberosal cells and the felogen constitutes the peridermis. In fact, the peridermis is a secondary protective tissue that replaces the epidermis in woody or secondary-growing plants.

The parenchymal tissue and the secondary phloem or sieve tissue originating from the cambium follow in this order. 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 xylem rings responsible for the growth in thickness of the plant. The number of xylem rings determines the age of the plant, since its formation occurs annually.

Under the bark is located the sapwood, active tissue or living wood of light color, whose function is the conduction of liquids from the roots to the foliage. The inner part of the trunk is made up of the heartwood -heart of the wood-, a tissue of dead cells of a dark color.

Types

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

Trees

Oak. Source: pixabay.com

Trees are woody-stemmed plants that have ramifications at a certain height from the ground. For a plant to be included in the category of trees, it must have a height of more 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, consisting of a rough and thick bark. Some examples of trees are oak (Quercus robur), pine (Pinus sp.), Saman (Samanea saman), carob (Ceratonia siliqua) or cedar (Cedrus libani).

Shrubbery

Shrubs are those woody plants of medium size that branch at ground level. Most of the shrubs have average heights between one and five meters.

Generally the branches are more than one, growing at ground level or from a main short stem. Examples of shrubs are lavender (Lavandula angustifolia), hydrangea (Hydrangea sp.), And blackberry (Morus nigra).

Bushes or climbers

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

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

Applications

Building

Wood for construction. Source: pixabay.com

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

Industry

Secondary products such as resin, latex and syrup are obtained from wood. Sawdust is a waste by-product 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 manufacture of paper and as vegetable fuel.

Medicinal

The woody bark of various species is used medicinally for the prevention and treatment of multiple diseases. The bark of trees such as pine (Pinus sp.), Cedar (Cedrela odorata), and 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 made from the bark and tender sprouts relieves colds, bronchitis, colds and coughs, as well as helping to reduce fever.

The bark of the cedar is used as an astringent, antirheumatic, balsamic, bronchitic and diuretic. Cedar can be used as an infusion or tea, bark decoction baths, or as a poultice for leaves and bark.

Palo santo contains the antioxidant limonene in its bark, which is used to dissolve kidney and urinary tract stones. Likewise, it is a preventive element of cancer, mammary tumors and of the pancreas; the ash from the wood is used to relieve external wounds.

References

1. González Ana María (2002) Secondary Structure of Stem II. Recovered at: biologia.edu.ar
2. Hernández García Alejandra (2018) Sapwood and Duramen. Know More Disclosure Magazine. Recovered at: sabermas.umich.mx
3. Woody secondary structure of the stem in dicotyledons (2018) La Web de Botánica. University of Granma. Recovered at: udg.co.cu
4. Woody plant (2018) Wikipedia, The Free Encyclopedia. Recovered at: wikipedia.org
5. Raven PH; Evert RF & Eichhorn SE (1991) Plant Biology, 2 vols. Ed. Reverté, SA 392 pp. ISBN: 9788429118414
6. Valla, Juan J. (1996) Botany. Morphology of superior plants. Southern Hemisphere Editorial. 352 pp. ISBN 9505043783.