Stem

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stem, supporting structure of a plant, serving also to conduct and to store food materials. The stems of herbaceous and of woody plants differ: those of herbaceous plants are usually green and pliant and are covered by a thin epidermis instead of by the bark of woody plants. There is relatively more pith in herbaceous stems, and the cambium, which increases the diameter of woody stems, is usually almost inactive; it is therefore characteristic of herbaceous stems that, although they increase in height, their increase in diameter is small. Most herbaceous plants are annuals; some have specialized underground stems (see bulb, corm, rhizome, and tuber) that store food and enable the plant to survive unfavorable growing conditions. Aerial stems may be specialized as tendrils, thorns, or runners (stolons); another specialization is the fleshy, moisture-retaining stem of many arid-land plants (such as most cacti and other succulents). Aerial stems are usually erect; however, in the climbing plants they require support and in others (e.g., melons) they are prostrate. The vascular system in the stem consists chiefly of xylem (upward-conducting) and phloem (downward-conducting) tissue, usually in vascular bundles arranged concentrically on either side of the cambium—the xylem (wood) inside, the phloem outside. In monocotyledonous plants, which generally lack cambium, the bundles are scattered throughout the stem tissue. The sap ducts are formed of elongated cells joined end to end; in the xylem the cell ends dissolve away completely to form continuous tubes and in the phloem they develop perforations and are called sieve plates. Herbaceous stems are marked externally by leaf and bud nodes; woody stems also bear lenticels (pores for transpiration), scars where leaves, twigs, and fruits have dropped off, and bud scars. The annual extension growth of a woody stem develops from a terminal bud usually protected by bud scales or stipules; when the scales fall away, a characteristic bud scar remains. The sap of certain stems contain gums, latexes, and resins used commercially; many are the source of wood of great economic importance.

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Stem

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Stem may refer to:

• Plant stem, the above ground structures that have vascular tissue and support leaves and flowers
• Word stem, the base part of a word not including inflectional morphemes
• Stem (bicycle part), connects the handlebars to the steer tube of a bicycle fork
• Stem (music), a part of a written musical note
• Crack stem, a device for smoking crack cocaine
• Stem (ship), the upright member mounted on the forward end of a vessel's keel, to which the strakes are attached
• Stem (skiing) is a technique in skiing
• "Stem", a song by Canadian musician Hayden from his 1995 album Everything I Long For
• Stem (band), an Estonian metal group
• The Stems, an Australian garage rock/power pop group from the 1980s

STEM may also refer to:

• Scanning transmission electron microscope
• STEM fields, Science, Technology, Engineering, and Mathematics, collectively considered core technological underpinnings of an advanced society
• Spatiotemporal Epidemiological Modeler, a free software developed by IBM

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