stem

stem¹

—stemless, adj. —stemlike, adj.

/stem/, n., v., stemmed, stemming.

n.

1. the ascending axis of a plant, whether above or below ground, which ordinarily grows in an opposite direction to the root or descending axis.

2. the stalk that supports a leaf, flower, or fruit.

3. the main body of that portion of a tree, shrub, or other plant which is above ground; trunk; stalk.

4. a cut flower: We bought roses at the flower market for 50¢ a stem.

5. a petiole; peduncle; pedicel.

6. a stalk of bananas.

7. something resembling or suggesting a leaf or flower stalk.

8. a long, slender part: the stem of a tobacco pipe.

9. the slender, vertical part of a goblet, wineglass, etc., between the bowl and the base.

10. Informal. a drinking glass having a stem.

11. the handle of a spoon.

12. a projection from the rim of a watch, having on its end a knob for winding the watch.

13. the circular rod in some locks about which the key fits and rotates.

14. the rod or spindle by which a valve is operated from outside.

15. the stock or line of descent of a family; ancestry or pedigree.

16. Gram. the underlying form, often consisting of a root plus an affix, to which the inflectional endings of a word are added, as tend-, the stem in Latin tendere "to stretch," the root of which is ten-. Cf. base¹ (def. 18), theme (def. 5).

17. Music. the vertical line forming part of a note.

18. stems, Slang. the legs of a human being.

19. the main or relatively thick stroke of a letter in printing.

v.t.

20. to remove the stem from (a leaf, fruit, etc.): Stem the cherries before cooking.

v.i.

21. to arise or originate: This project stems from last week's lecture.

[bef. 900; ME; OE stemn, stefn, equiv. to ste- (var. of sta-, base of standan to STAND) + -mn- suffix; akin to G Stamm stem, tribe; see STAFF¹]

stem²

/stem/, v., stemmed, stemming, n.

v.t.

1. to stop, check, or restrain.

2. to dam up; stop the flow of (a stream, river, or the like).

3. to tamp, plug, or make tight, as a hole or joint.

4. Skiing. to maneuver (a ski or skis) in executing a stem.

5. to stanch (bleeding).

v.i.

6. Skiing. to execute a stem.

n.

7. Skiing. the act or instance of a skier pushing the heel of one or both skis outward so that the heels are far apart, as in making certain turns or slowing down.

[1400-50; late ME stemmen < ON stemma to dam or MLG stemmen]

stem³

/stem/, v.t., stemmed, stemming.

1. to make headway against (a tide, current, gale, etc.).

2. to make progress against (any opposition).

[1585-95; v. use of STEM⁴]

stem⁴

/stem/, n. Naut.

1. (at the bow of a vessel) an upright into which the side timbers or plates are jointed.

2. the forward part of a vessel (often opposed to stern).

[bef. 900; continuing OE stefn, stemn end-timber; special use of STEM¹; ME stampne, stamyn(e) appar. < the c. ON stamn, stafn in same sense]

stem⁵

/stem/, v.t., stemmed, stemming.

to arrange the loading of (a merchant vessel) within a specified time.

[1895-1900; var. of steven to direct one's course < ON stefna to sail directly, aim, deriv. of stafn STEM⁴]

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Plant axis that emerges from the roots, supports the branches, bears buds and shoots with leaves, and contains the vascular (conducting) tissues (xylem and phloem) that transport water, minerals, and food to other parts of the plant.

The pith (a central core of spongy tissue) is surrounded by strands (in dicots; see cotyledon) or bundles (in monocots) of conducting xylem and phloem, then by the cortex and outermost epidermis, or bark. The cambium (an area of actively dividing cells) lies just below the bark. Lateral buds and leaves grow out of the stem at intervals called nodes; the intervals on the stem between the nodes are called internodes. In flowering plants, various stem modifications (rhizome, corm, tuber, bulb, stolon) let the plant survive dormantly for years, store food, or sprout asexually. All green stems perform photosynthesis, as do leaves; in plants such as the cacti (see cactus) and asparagus, the stem is the chief site of photosynthesis.

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▪ plant

      in botany, the plant axis that bears buds and shoots with leaves and, at its basal end, roots. The stem is the stalk of a plant or the main trunk of a tree. The stem conducts water, minerals, and food to other parts of the plant; it may also store food, and green stems themselves produce food. In most plants the stem is the major vertical shoot, in some it is inconspicuous, and in others it is modified and resembles other plant parts (e.g., underground stems may look like roots).

      The first rudiment of the young stem, or shoot, of an embryonic plant appears from the seed after the root has first protruded. The growing portion at the apex of the shoot is the terminal bud of the plant, and by the continued development of this bud and its adjacent tissues, the stem increases in height. Lateral buds and leaves grow out of the stem at intervals called nodes; the intervals on the stem between the nodes are called internodes. The number of leaves that appear at a node depends on the species of plant; one leaf per node is common, but two or or more leaves may grow at the nodes of some species. When a leaf drops off a stem at the end of a growing season, it leaves a scar on the stem because of the severing of the vascular (conducting) bundles that had connected stem and leaf. As the stem continues to grow, lateral buds are produced that develop into lateral shoots more or less resembling the parent stem, and these ultimately determine the branching of the plant. In trees the lateral shoots develop into branches, from which other lateral shoots, called branchlets, or twigs, arise. The point at which a leaf diverges in axis from a stem is called the axil. A bud formed in the axil of a previously formed leaf is called an axillary bud, and it, like the leaves, is produced from the tissues of the stem. During the development of such buds, vascular bundles are formed within them that are continuous with those of the stem.

      The primary functions of the stem are to support the leaves; to conduct water and minerals to the leaves, where they can be converted into usable products by photosynthesis; and to transport these products from the leaves to other parts of the plant, including the roots. The stem conducts water and nutrient minerals from their site of absorption in the roots to the leaves by means of certain vascular tissues in the xylem (q.v.). The movement of synthesized foods from the leaves to other plant organs occurs chiefly through other vascular tissues in the stem called phloem (q.v.). Food and water are also frequently stored in the stem. Examples of food-storing stems include such specialized forms as tubers, rhizomes, and corms and the woody stems of trees and shrubs. Water storage is developed to a high degree in the stems of cacti.

      In the stems of young dicotyledons (dicotyledon) and gymnosperms (gymnosperm), the vascular bundles (xylem and phloem) are arranged in a circle around a central core of spongy ground tissue called the pith. Surrounding the vascular bundles is a layer that varies in thickness in different species and is called the cortex. Surrounding this and comprising the exterior surface of the stem is a layer called the epidermis. In plants with woody stems, a variety of secondary tissues are added to these primary tissues. Among the most important of these is a ring of meristematic cells that in turn give rise to the vascular cambium. This tissue arises between the primary xylem and phloem and gives rise to secondary phloem on the outside and secondary xylem on the inside; the latter tissue is the wood of trees.

      All green stems carry on the photosynthetic work of the leaves, and in most cacti this function is performed to a predominant degree by the stem. Other plants in which food-making is carried on chiefly by the stem include the asparagus. Many plants are annuals and complete their life cycles in one growing season, after which the entire plant, including the stem, dies. In biennial plants the lower part of the stem persists after the first growing season and bears buds from which an erect stem arises during the second growing season. In perennial plants the short stem may produce new shoots for many years. Plants producing woody stems are called trees and shrubs. The latter produce branches from or near the ground, while the former have conspicuous trunks.

      In general, the habit of a stem is erect or ascending, but it may lie prostrate on the ground, as in the sweet potato and strawberry. A stem may climb on rocks or plants by means of rootlets, as in ivy; other vines have twining stems that twist around a supporting plant in a spiral manner, as in the morning-glory, honeysuckle, and hop. In other cases, climbing plants are supported by tendrils that may be specialized stems, as in the grape and passionflower. In tropical climates twining plants often form thick woody stems and are called lianas, while in temperate regions they are generally herbaceous vines. A stolon is a stem that curves toward the ground and, on reaching a moist spot, takes root and forms an upright stem and ultimately a separate plant. Among the subterranean stems are the rhizome, corm, and tuber (qq.v.). In some plants the stem does not elongate during its early development but instead forms a short conical structure from which a crown of leaves arises. These may form a bulb (as in the onion and lily), a head (cabbage, lettuce), or a rosette (dandelion, plantain).

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