stem

STEM

abbr. science, technology, engineering, and mathematics

stem¹

S0735300 (stĕm)n.1. a. The main ascending part of a plant; a stalk or trunk.b. A slender stalk supporting or connecting another plant part, such as a leaf or flower.c. A banana stalk bearing several bunches of bananas.2. A connecting or supporting part, especially:a. The tube of a tobacco pipe.b. The slender upright support of a wineglass or goblet.c. The small projecting shaft with an expanded crown by which a watch is wound.d. The rounded rod in the center of certain locks about which the key fits and is turned.e. The shaft of a feather or hair.f. The upright stroke of a typeface or letter.g. Music The vertical line extending from the head of a note.3. The main line of descent of a family.4. Linguistics The main part of a word to which affixes are added.5. Nautical The curved upright beam at the fore of a vessel into which the hull timbers are scarfed to form the prow.6. The tubular glass structure mounting the filament or electrodes in an incandescent bulb or vacuum tube.v. stemmed, stem·ming, stems v.intr. To have or take origin or descent: Her success stems mostly from hard work.v.tr.1. To remove the stem of: stemmed the apples.2. To provide with a stem: wine glasses that are stemmed.3. To make headway against (a tide or current, for example).Idiom: from stem to stern From one end to another.

[Middle English, from Old English stefn, stemn; see stā- in Indo-European roots.]Synonyms: stem¹, arise, derive, emanate, flow, issue, originate, proceed, rise, spring
These verbs mean to come forth or come into being: customs that stem from the past; misery that arose from war; rights that derive from citizenship; disapproval that emanated from the teacher; happiness that flows from their friendship; prejudice that issues from fear; a proposal that originated in the Congress; a mistake that proceeded from carelessness; rebellion that rises in the provinces; new industries that spring from technology.

stem²

S0735300 (stĕm)v. stemmed, stem·ming, stems v.tr.1. To stop or stanch (a flow): stemmed the bleeding.2. To restrain or stop: wanted to stem the growth of government.3. To plug or tamp (a blast hole, for example).4. Sports To turn (a ski, usually the uphill ski) by moving the heel outward.v.intr. Sports To stem a ski or both skis, as in making a turn.

[Middle English stemmen, from Old Norse stemma.]

stem

(stɛm) n1. (Botany) the main axis of a plant, which bears the leaves, axillary buds, and flowers and contains a hollow cylinder of vascular tissue2. (Botany) any similar subsidiary structure in such plants that bears a flower, fruit, or leaf3. (Botany) a corresponding structure in algae and fungi4. any long slender part, such as the hollow part of a tobacco pipe that lies between the bit and the bowl, or the support between the base and the bowl of a wineglass, goblet, etc5. (Plants) a banana stalk with several bunches attached6. (Heraldry) the main line of descent or branch of a family7. (Mechanical Engineering) a round pin in some locks on which a socket in the end of a key fits and about which it rotates8. (Mechanical Engineering) any projecting feature of a component: a shank or cylindrical pin or rod, such as the pin that carries the winding knob on a watch9. (Linguistics) linguistics the form of a word that remains after removal of all inflectional affixes; the root of a word, esp as occurring together with a thematic element. Compare root¹⁹10. (Printing, Lithography & Bookbinding) the main, usually vertical, stroke of a letter or of a musical note such as a minim11. (Electrical Engineering) electronics the tubular glass section projecting from the base of a light bulb or electronic valve, on which the filament or electrodes are mounted12. (Nautical Terms) a. the main upright timber or structure at the bow of a vesselb. the very forward end of a vessel (esp in the phrase from stem to stern)vb, stems, stemming or stemmed13. (usually foll by: from) to be derived; originate: the instability stems from the war. 14. (Nautical Terms) (tr) to make headway against (a tide, wind, etc)15. (tr) to remove or disengage the stem or stems from16. (tr) to supply (something) with a stem or stems[Old English stemn; related to Old Norse stafn stem of a ship, German Stamm tribe, Gothic stōma basis, Latin stāmen thread] ˈstemˌlike adj ˈstemmer n

stem

(stɛm) vb, stems, stemming or stemmed1. (tr) to restrain or stop (the flow of something) by or as if by damming up2. (tr) to pack tightly or stop up3. (Skiing) skiing to manoeuvre (a ski or skis), as in performing a stemn (Skiing) skiing a technique in which the heel of one ski or both skis is forced outwards from the direction of movement in order to slow down or turn[C15 stemmen, from Old Norse stemma; related to Old Norse stamr blocked, stammering, German stemmen to prop; see stammer] ˈstemmer n

Stem

(stɛm) n (Music, other) die Stem (di) the South African national anthem until 1991, when part of it was incorporated into the current anthem, Nkosi Sikelel' iAfrika. See Nkosi Sikelel' iAfrika[C19: from Afrikaans, the call]

stem¹

(stɛm)

n., v. stemmed, stem•ming. n. 1. the ascending axis of a plant, whether above or below ground, which ordinarily grows in an opposite direction to the root. 2. the stalk that supports a leaf, flower, or fruit. 3. a stalk of bananas. 4. something resembling or suggesting a leaf or flower stalk. 5. a long, slender part: the stem of a tobacco pipe. 6. the slender, vertical part of a goblet, wineglass, etc., between the bowl and the base. 7. a projection from the rim of a watch, having on its end a knob for winding the watch. 8. the circular rod in some locks about which the key fits and rotates. 9. the stock or line of descent of a family, esp. its original ancestry. 10. the underlying form of a word, consisting of a root alone or a root plus an affix, to which inflectional endings may be added. 11. the vertical line forming part of a musical note. 12. the main or relatively thick stroke of a letter in printing. v.t. 13. to remove the stem from (a leaf, fruit, etc.). v.i. 14. to arise or originate (usu. fol. by from). [before 900; (n.) Middle English; Old English stemn, stefn, akin to Middle Dutch, Middle Low German, Old High German stam stem, Old Saxon, Old Norse stamn stem³] stem′less, adj. stem′like`, adj.

stem²

(stɛm)

v. stemmed, stem•ming,
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. to maneuver (a ski or skis) in executing a stem. 5. to stanch (bleeding). v.i. 6. to execute a stem. n. 7. an act or instance whereby a skier pushes the heel of one or both skis outward, as in making certain turns or to slow down. [1400–50; late Middle English stemmen < Old Norse stemma to dam]

stem⁴

(stɛm)

n., v. stemmed, stem•ming. n. 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). v.t. 3. to make headway against (a tide, current, gale, etc.). 4. to make progress against (any opposition). [before 900; continuing Old English stefn, stemn (see stem¹); Middle English stampne, stamyn(e) appar. < the c. Old Norse stamn, stafn]

stem

(stĕm)1. The main, often long or slender part of a plant that usually grows upward above the ground and supports other parts, such as branches and leaves. Some underground plant structures, such as rhizomes and corms, are stems rather than roots.2. A slender stalk supporting or connecting another plant part, such as a leaf or flower.

stem

- The stem of a tree is etymologically the upright part, the part that "stands" up, from its Germanic base sta-, "stand."See also related terms for stands.

stem

Past participle: stemmed
Gerund: stemming

Imperative
stem
stem

Present
I stem
you stem
he/she/it stems
we stem
you stem
they stem

Preterite
I stemmed
you stemmed
he/she/it stemmed
we stemmed
you stemmed
they stemmed

Present Continuous
I am stemming
you are stemming
he/she/it is stemming
we are stemming
you are stemming
they are stemming

Present Perfect
I have stemmed
you have stemmed
he/she/it has stemmed
we have stemmed
you have stemmed
they have stemmed

Past Continuous
I was stemming
you were stemming
he/she/it was stemming
we were stemming
you were stemming
they were stemming

Past Perfect
I had stemmed
you had stemmed
he/she/it had stemmed
we had stemmed
you had stemmed
they had stemmed

Future
I will stem
you will stem
he/she/it will stem
we will stem
you will stem
they will stem

Future Perfect
I will have stemmed
you will have stemmed
he/she/it will have stemmed
we will have stemmed
you will have stemmed
they will have stemmed

Future Continuous
I will be stemming
you will be stemming
he/she/it will be stemming
we will be stemming
you will be stemming
they will be stemming

Present Perfect Continuous
I have been stemming
you have been stemming
he/she/it has been stemming
we have been stemming
you have been stemming
they have been stemming

Future Perfect Continuous
I will have been stemming
you will have been stemming
he/she/it will have been stemming
we will have been stemming
you will have been stemming
they will have been stemming

Past Perfect Continuous
I had been stemming
you had been stemming
he/she/it had been stemming
we had been stemming
you had been stemming
they had been stemming

Conditional
I would stem
you would stem
he/she/it would stem
we would stem
you would stem
they would stem

Past Conditional
I would have stemmed
you would have stemmed
he/she/it would have stemmed
we would have stemmed
you would have stemmed
they would have stemmed

Thesaurus

Noun	1.	stem - (linguistics) the form of a word after all affixes are removed; "thematic vowels are part of the stem"root word, root, theme, radical, baselinguistics - the scientific study of languagedescriptor, form, signifier, word form - the phonological or orthographic sound or appearance of a word that can be used to describe or identify something; "the inflected forms of a word can be represented by a stem and a list of inflections to be attached"
	2.	stem - a slender or elongated structure that supports a plant or fungus or a plant part or plant organstalkgynophore - the stalk of a pistil that raises it above the receptaclecarpophore - a slender stalk that furnishes an axis for a carpelcorn stalk, cornstalk - the stalk of a corn plantfilament - the stalk of a stamenfunicle, funiculus - the stalk of a plant ovule or seedpetiolule - the stalk of a leafletcane - a strong slender often flexible stem as of bamboos, reeds, rattans, or sugar caneplant organ - a functional and structural unit of a plant or fungussporangiophore - stalk bearing one or more sporangiacutting, slip - a part (sometimes a root or leaf or bud) removed from a plant to propagate a new plant through rooting or graftingtuber - a fleshy underground stem or root serving for reproductive and food storagerhizome, rootstalk, rootstock - a horizontal plant stem with shoots above and roots below serving as a reproductive structureaxis - the main stem or central part about which plant organs or plant parts such as branches are arrangedcaudex - woody stem of palms and tree fernsinternode - a segment of a stem between two nodesbeanstalk - stem of a bean plantcladode, cladophyll, phylloclad, phylloclade - a flattened stem resembling and functioning as a leafreceptacle - enlarged tip of a stem that bears the floral partscaudex, stock - persistent thickened stem of a herbaceous perennial plantstipe - supporting stalk or stem-like structure especially of a pistil or fern frond or supporting a mushroom capflower stalk, scape - erect leafless flower stalk growing directly from the ground as in a tulipleafstalk, petiole - the slender stem that supports the blade of a leafbulb - a modified bud consisting of a thickened globular underground stem serving as a reproductive structurecorm - solid swollen underground bulb-shaped stem or stem base and serving as a reproductive structureleaf node, node - (botany) the small swelling that is the part of a plant stem from which one or more leaves emergebranch - a division of a stem, or secondary stem arising from the main stem of a plantculm - stem of plants of the Gramineaehalm, haulm - stems of beans and peas and potatoes and grasses collectively as used for thatching and beddingtree trunk, trunk, bole - the main stem of a tree; usually covered with bark; the bole is usually the part that is commercially useful for lumber
	3.	stem - cylinder forming a long narrow part of somethingshankanchor, ground tackle - a mechanical device that prevents a vessel from movinghandgrip, handle, grip, hold - the appendage to an object that is designed to be held in order to use or move it; "he grabbed the hammer by the handle"; "it was an old briefcase but it still had a good grip"key - metal device shaped in such a way that when it is inserted into the appropriate lock the lock's mechanism can be rotatednail - a thin pointed piece of metal that is hammered into materials as a fastenerpin - a small slender (often pointed) piece of wood or metal used to support or fasten or attach thingswineglass - a glass that has a stem and in which wine is servedcylinder - a surface generated by rotating a parallel line around a fixed line
	4.	stem - the tube of a tobacco pipepipe, tobacco pipe - a tube with a small bowl at one end; used for smoking tobaccotube, tubing - conduit consisting of a long hollow object (usually cylindrical) used to hold and conduct objects or liquids or gases
	5.	stem - front part of a vessel or aircraft; "he pointed the bow of the boat toward the finish line"fore, prow, bowfront - the side that is seen or that goes firstvessel, watercraft - a craft designed for water transportation
	6.	stem - a turn made in skiing; the back of one ski is forced outward and the other ski is brought parallel to itstem turnturning, turn - the act of changing or reversing the direction of the course; "he took a turn to the right"
Verb	1.	stem - grow out of, have roots in, originate in; "The increase in the national debt stems from the last war"originate in - come from
	2.	stem - cause to point inward; "stem your skis"orient - cause to point; "Orient the house towards the West"
	3.	stem - stop the flow of a liquid; "staunch the blood flow"; "stem the tide"stanch, staunch, haltcheck - arrest the motion (of something) abruptly; "He checked the flow of water by shutting off the main valve"
	4.	stem - remove the stem from; "for automatic natural language processing, the words must be stemmed"remove, take away, withdraw, take - remove something concrete, as by lifting, pushing, or taking off, or remove something abstract; "remove a threat"; "remove a wrapper"; "Remove the dirty dishes from the table"; "take the gun from your pocket"; "This machine withdraws heat from the environment"

stem

¹noun stalk, branch, trunk, shoot, stock, axis, peduncle He cut the stem for her with his knife and handed her the flower.stem from something originate from, be caused by, derive from, arise from, flow from, emanate from, develop from, be generated by, be brought about by, be bred by, issue forth from Much of the instability stems from the economic effects of the war.

stem

²verb stop, hold back, staunch, stay (archaic), check, contain, dam, curb, restrain, bring to a standstill, stanch He was still conscious, trying to stem the bleeding with his right hand.

stem

nounThe main part of a word to which affixes are attached:base, root, theme.verbTo have as a source:arise, come, derive, emanate, flow, issue, originate, proceed, rise, spring, upspring.

Translations

发生于堵住来自树干梗

stem¹

(stem) noun1. the part of a plant that grows upward from the root, or the part from which a leaf, flower or fruit grows; a stalk. Poppies have long, hairy, twisting stems. 茎、梗、（树）干 2. the narrow part of various objects, eg of a wine-glass between the bowl and the base. the stem of a wine-glass / of a tobacco-pipe.酒杯的脚3. the upright piece of wood or metal at the bow of a ship. As the ship struck the rock, she shook from stem to stern.船头 verb – past tense, past participle stemmed – (with from) to be caused by. Hate sometimes stems from envy. 发生（于） -stemmeda thick-stemmed plant; He smoked a short-stemmed pipe.带柄的

stem²

(stem) – past tense, past participle stemmed – verb to stop (a flow, eg of blood). 堵住

stem

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 cambiumcambium
, thin layer of generative tissue lying between the bark and the wood of a stem, most active in woody plants. The cambium produces new layers of phloem on the outside and of xylem (wood) on the inside, thus increasing the diameter of the stem.
..... Click the link for more information. , 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 bulbbulb,
thickened, fleshy plant bud, usually formed under the surface of the soil, which carries the plant over from one blooming season to another. It may have many fleshy layers (as in the onion and hyacinth) or thin dry scales (as in some lilies)—both of which are highly
..... Click the link for more information. , cormcorm,
short, thickened underground stem, usually covered with papery leaves. A corm grows vertically, producing buds at the upper nodes and roots from the lower surface. Corms serve as organs of food storage and in some plants (e.g.
..... Click the link for more information. , rhizomerhizome
or rootstock,
fleshy, creeping underground stem by means of which certain plants propagate themselves. Buds that form at the joints produce new shoots.
..... Click the link for more information. , and tubertuber,
enlarged tip of a rhizome (underground stem) that stores food. Although much modified in structure, the tuber contains all the usual stem parts—bark, wood, pith, nodes, and internodes.
..... Click the link for more information. ) 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 (woodwood,
botanically, the xylem tissue that forms the bulk of the stem of a woody plant. Xylem conducts sap upward from the roots to the leaves, stores food in the form of complex carbohydrates, and provides support; it is made up of various types of cells specialized for each of
..... Click the link for more information. ) 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 sapsap,
fluid in plants consisting of water and dissolved substances. Cell sap refers to this fluid present in the large vacuole, or cell cavity, that occupies most of the central portion of mature plant cells.
..... Click the link for more information. of certain stems contain gums, latexes, and resins used commercially; many are the source of wood of great economic importance.

Stem

The organ of vascular plants that usually develops branches and bears leaves and flowers. On woody stems a branch that is the current season's growth from a bud is called a twig. The stems of some species produce adventitious roots. See Root (botany)

General characteristics

While most stems are erect, aerial structures, some remain underground, others creep over or lie prostrate on the surface of the ground, and still others are so short and inconspicuous that the plants are said to be stemless, or acaulescent. When stems lie flattened immediately above but not on the ground, with tips curved upward, they are said to be decumbent, as in juniper. If stems lie flat on the ground but do not root at the nodes (joints), the stem is called procumbent or prostrate, as in purslane. If a stem creeps along the ground, rooting at the nodes, it is said to be repent or creeping, as in ground ivy.

Most stems are cylindrical and tapering, appearing circular in cross section; others may be quadrangular or triangular.

Herbaceous stems (annuals and herbaceous perennials) die to the ground after blooming or at the end of the growing season. They usually contain little woody tissue. Woody stems (perennials) have considerable woody supporting tissue and live from year to year. A woody plant with no main stem or trunk, but usually with several stems developed from a common base at or near the ground, is known as a shrub.

External features

A shoot or branch usually consists of a stem, or axis, and leafy appendages. Stems have several distinguishing features. They arise either from the epicotyl of the embryo in a seed or from buds. The stem bears both leaves and buds at nodes, which are separated by leafless regions or internodes, and sometimes roots and flowers (see illustration).

Winter woody twig (horse chestnut) showing apical dominance

The nodes are the regions of the primary stem where leaves and buds arise. The number of leaves at a node is usually specific for each plant species. In deciduous plants which are leafless during winter, the place of former attachment of a leaf is marked by the leaf scar. The scar is formed in part by the abscission zone formed at the base of the leaf petiole. The stem regions between nodes are called internodes. Internode length varies greatly among species, in different parts of the same stem, and under different growing conditions.

Lenticels are small, slightly raised or ridged regions of the stem surface that are composed of loosely arranged masses of cells in the bark. Their intercellular spaces are continuous with those in the interior of the stem, therefore permitting gas exchange similar to the stomata that are present before bark initiation.

There are three major types of stem branching: dichoto-mous, monopodial, and sympodial. Dichotomy occurs by a division of the apical meristem to form two new axes. If the terminal bud of an axis continues to grow and lateral buds grow out as branches, the branching is called monopodial. If the apical bud terminates growth in a flower or dies back and one or more axillary buds grow out, the branching is called sympodial. Often only one bud develops so that what appears to be single axis is in fact composed of a series of lateral branches arranged in linear sequence.

The large and conspicuous stems of trees and shrubs assume a wide variety of distinctive forms. Columnar stems are basically unbranched and form a terminal leaf cluster, as in palms, or lack obvious leaves, as in cacti. Branching stems have been classified either as excurrent, when there is a central trunk and a conical leaf crown, as in firs and other conifers, or as decur-rent (or deliquescent), when the trunk quickly divides up into many separate axes so that the crown lacks a central trunk, as in elm. See Tree

Internal features

The stem is composed of the three fundamental tissue systems that are found also in all other plant organs: the dermal (skin) system, consisting of epidermis in young stems and peridem in older stems of many species; the vascular (conducting) system, consisting of xylem (water conduction) and phloem (food conduction); and the fundamental or ground tissue system, consisting of parenchyma and sclerenchyma tissues in which the vascular tissues are embedded. The arrangement of the vascular tissues varies in stems of different groups of plants, but frequently these tissues form a hollow cylinder enclosing a region of ground tissue called pith and separated from the dermal tissue by another region of ground tissue called cortex. See Cortex (plant), Epidermis (plant), Phloem, Pith, Sclerenchyma, Xylem

Part of the growth of the stem results from the activity of the apical meristem located at the tip of the shoot. The derivatives of this meristem are the primary tissues; epidermis, primary vascular tissues, and the ground tissues of the cortex and pith. In many species, especially those having woody stems, secondary tissues are added to the primary. These tissues are derived from the lateral meristems, oriented parallel with the sides of the stem: cork cambium (phellogen), which gives rise to the secondary protective tissue periderm, which consists of phellum (cork), phellogen (cork cambium), and phelloderm (secondary cortex) and which replaces the epidermis; and vascular cambium, which is inserted between the primary xylem and phloem and forms secondary xylem (wood) and phloem. See Apical meristem, Lateral meristem

The vascular tissues and the closely associated ground tissues—pericycle (on the outer boundary of vascular region), interfascicular regions (medullary or pith rays), and frequently also the pith—may be treated as a unit called the stele. The variations in the arrangement of the vascular tissues serve as a basis for distinguishing the stelar types. The word stele means column and thus characterizes the system of vascular and associated ground tissues as a column. This column is enclosed within the cortex, which is not part of the stele.

Stem

in linguistics, the part of a word that bears the lexical meaning of that word. A stem does not include inflectional affixes such as endings. It may consist of one root, such as dom (“house”); of a root with one or more derivational suffixes, such as dom-ik (“house” [diminutive]), kras-n-yi (“red”; -yi is an ending), and kras-n-en’k-ii (“red” [affectionate diminutive]; -ii is an ending); of a root and a prefix, as in pri-gorod (“suburb”); or of a root, a prefix, and a suffix, such as s-del-a-t’(“to do” [perfective]; -t’ is the infinitive suffix indicating the function of the verb in its clause and is not part of the stem). In some languages the stem may also include infixes.

Stem

in higher plants, the axial organ that together with leaves constitutes a shoot. Stems transport water and other substances from the roots to the leaves. The branching of the stem and the ordered arrangement of leaves, flowers, and fruits increase the assimilative surface of a plant. Stems often participate in the storage of water and reserve nutrients and in photosynthesis. The stem regions from which lateral organs, including branches and leaves, depart are called nodes, and the areas between nodes are called internodes.

Stems may be herbaceous or woody. The main stem of woody plants is called a trunk. Stems are generally cylindrical in shape, although they may also be triangular (in sedges), quadrangular (in mints), polyhedral, or flattened (in cacti). Their habit may be erect, prostrate, creeping, or climbing. Some are aerial structures, whereas others remain underground.

Stems range in length from 1–1.5 mm (in freshwater duckweeds) to 200–300 m (in tropical rattan palms). The diameter may range from fractions of a millimeter (in mosses) to 10–11 m (in baobabs and sequoias). A stem increases in length as a result of the activity of the shoot’s apical meristem, which constitutes the growing point. Besides apical growth, grasses and other plants are characterized by intercalary growth at the bases of the internodes.

A stem is composed of an epidermis externally and a central cylinder, or stele, internally. Between the epidermis and stele is the primary cortex, whose internal parenchymatous layer is converted into the endodermis. The primary cortex borders on the peripheral part of the stele—the pericycle—which is represented by parenchymatous or mechanical tissue. The pericycle is absent in some plants.

The stele consists mostly of vascular tissues; the phloem is outside the xylem. In the center of the stem of leafy mosses there is a vascular bundle, the elements of which are only externally similar to the conducting elements of the phloem and xylem. In vascular plants the development of the procambium precedes the formation of vascular tissues. In club mosses there is no pith, and the xylem is divided into ribbonlike strands surrounded by phloem. In horsetails closed collateral bundles, with carinal cavities instead of xylem, are arranged around a central hollow cavity. In ferns vascular tissues form a ring around the pith.

The stems of seed plants have fascicular and continuous vascular systems divided by parenchymatous medullary rays that extend outward. The external part of the procambium becomes differentiated into the primary phloem, on whose periphery mechanical fibers often develop; the internal part of the procambium becomes differentiated into the primary xylem. A layer of cells forming the cambium is found between the vascular tissues. The cambium deposits elements of the secondary phloem externally and elements of the secondary xylem internally, resulting in the thickening of the stele.

Unlike the nodal part of the stem, the central part of the inter-nodes lacks leaf and branch gaps (lacunae). Trilacunar nodes are common in dicotyledons, for example, in apples. Less common are monolacunar and multilacunar nodes; the former are typical of lilacs, and the latter of elders. The most active secondary thickening is characteristic of perennial woody plants, in whose secondary xylem and, sometimes, phloem annual, or growth, rings may be observed. With age, as a result of the development of the periderm, the primary cortex and, later, the outer part of the phloem atrophy and form the cortex.

Most monocotyledons have the type of closed collateral bundles characteristic of palms; as a result the bundles are arranged diffusely in transverse sections. There is a tendency toward a circular arrangement of bundles only in a few grasses with culms, in spiderworts, and in yams. Secondary thickening is characteristic only of arborescent Liliaceae, for example, aloes and dracaena palms; the meristem, which is formed in the pericycle or primary cortex, gives rise to concentric bundles and interfascicular, often lignifying, parenchyma.

REFERENCES

Serebriakov, I. G. Morfologiia vegetativnykh organov vysshikh rastenii. Moscow, 1952.
Meier, K. I. Morfogeniia vysshikh rastenii. Moscow, 1958.
Eames, A. Morfologiia tsvetkovykh rastenii. Moscow, 1964. (Translated from English.)
Botanika, vol. 1. Edited by L. V. Kudriashov. Moscow, 1966.
Esau, K. Anatomiia rastenii. Moscow, 1969. (Translated from English.)

L. I.LOTOVA

stem

[stem] (botany) The organ of vascular plants that usually develops branches and bears leaves and flowers. (engineering) The heavy iron rod acting as the connecting link between the bit and the balance of the string of tools on a churn rod. To insert packing or tamping material in a shothole. (navigation) To make headway against an obstacle, as a current. (naval architecture) The foremost part of a ship's hull.

STEM

[stem] (electronics) scanning transmission electron microscope

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web, 1 1. The portion of a truss or girder between the chords or flanges, whose principal function is to resist shear on the span. 2. A core divider in a hollow masonry unit.

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¹1. the main axis of a plant, which bears the leaves, axillary buds, and flowers and contains a hollow cylinder of vascular tissue 2. any similar subsidiary structure in such plants that bears a flower, fruit, or leaf 3. a corresponding structure in algae and fungi 4. a banana stalk with several bunches attached 5. a round pin in some locks on which a socket in the end of a key fits and about which it rotates 6. any projecting feature of a component: a shank or cylindrical pin or rod, such as the pin that carries the winding knob on a watch 7. Electronics the tubular glass section projecting from the base of a light bulb or electronic valve, on which the filament or electrodes are mounted 8. a. the main upright timber or structure at the bow of a vessel b. the very forward end of a vessel (esp in the phrase from stem to stern)

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² Skiing a technique in which the heel of one ski or both skis is forced outwards from the direction of movement in order to slow down or turn

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(Science, Technology, Engineering, Mathematics) An umbrella term used by the U.S. government for the major categories of highly skilled occupations. See high tech.

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stem the tide

stem to stern

from stem to stern

stem from (something)

from stem to stern

stem from something

from soup to nuts

stem the tide

stem to stern

stem the tide

stem the flow

from soup to nuts

from stem to stern

from ˌsoup to ˈnuts

from ˌstem to ˈstern

ˌstem the ˈtide (of something)

stem from

from stem to stern

from soup to nuts

stem the tide, to

stem to stern, from

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stem,

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General characteristics

External features

Internal features

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REFERENCES

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Patient discussion about stem

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Synonyms for stem

noun stalk

Synonyms

phrase stem from something

Synonyms

verb stop

Synonyms

Synonyms for stem

noun the main part of a word to which affixes are attached

Synonyms

verb to have as a source

Synonyms

Synonyms for stem

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