A stem is one of two main structural axes of a vascular plant Vascular plants are those plants that have lignified tissues for conducting water, minerals, and photosynthetic products through the plant. Vascular plants include the ferns, clubmosses, flowering plants, conifers and other gymnosperms. Scientific names for the group include Tracheophyta and Tracheobionta, but neither name is very widely used.[. The stem is normally divided into nodes and internodes, the nodes hold buds In botany, a bud is an undeveloped or embryonic shoot and normally occurs in the axil of a leaf or at the tip of the stem. Once formed, a bud may remain for some time in a dormant condition, or it may form a shoot immediately which grow into one or more leaves In botany, a leaf is an above-ground plant organ specialized for photosynthesis. For this purpose, a leaf is typically flat and thin. There is continued debate about whether the flatness of leaves evolved to expose the chloroplasts to more light or to increase the absorption of carbon dioxide. In either case, the adaption was made at the expense, inflorescence An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified. The modifications can involve the length and the nature of the internodes and the (flowers), cones A cone is an organ on plants in the division Pinophyta (conifers) that contains the reproductive structures. The familiar woody cone is the female cone, which produces seeds. The male cones, which produce pollen, are usually herbaceous and much less conspicuous even at full maturity. The name "cone" derives from the fact that the shape or other stems etc. The internodes distance one node from another. The term shoots Shoots are new plant growth, they can include stems, flowering stems with flower buds, leaves. The new growth from seed germination that grows upward is a shoot where leaves will develop. In the spring, perennial plant shoots are the new growth that grows from the ground in herbaceous plants or the new stem and/or flower growth that grows on woody is often confused with stems; shoots generally refer to new fresh plant growth and does include stems but also to other structures like leaves or flowers. The other main structural axis of plants is the root In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating (growing up above the ground or especially above water). Furthermore, a stem normally occurring below ground is not exceptional either (see rhizome). So, it is. In most plants stems are located above the soil surface but some plants have underground stems Underground stems are modified plant structures that derive from stem tissue but exist under the soil surface. Plants have two axes of growth, which can be best seen from seed germination and growth. Seedlings develop two structures or axes of growth, one that develops upward out of the soil, called stems, and structures that develop downward.
Stems have four main functions which are:[1]
- Support for and the elevation of leaves, flowers A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to mediate the union of male sperm with female ovum in order to produce seeds. The process begins with pollination, is followed by fertilization, leading to the formation and dispersal of the seeds. For and fruits The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state, such as apples, oranges, grapes, strawberries, juniper berries and bananas, or the similar-looking structures in other. The stems keep the leaves in the light and provide a place for the plant to keep its flowers and fruits.
- Transport of fluids between the roots and the shoots in the xylem In vascular plants, xylem is one of the two types of transport tissue, phloem being the other. The word "xylem" is derived from classical Greek ξυλον , "wood", and indeed the best-known xylem tissue is wood, though it is found throughout the plant. Its basic function is to transport water but it also transports some and phloem In vascular plants, phloem is the living tissue that carries organic nutrients , particularly sucrose, a sugar, to all parts of the plant where needed. In trees, the phloem is the innermost layer of the bark, hence the name, derived from the Greek word φλόος (phloos) "bark". The phloem is concerned mainly with the transport of.
- Storage of nutrients.
- The production of new living tissue. The normal life span of plant cells is one to three years. Stems have cells called meristems A meristem is the tissue in all plants consisting of undifferentiated cells and found in zones of the plant where growth can take place that annually generate new living tissue.
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Specialized terms for stems
Stem showing internode and nodes plus leaf petioles.Stems are often specialized for storage, asexual reproduction, protection or photosynthesis, including the following:
- Acaulescent - plants with very long stems that doesnt have no stems. The leaves appear to rise out of the ground, e.g. some Viola Viola is a genus of flowering plants in the violet family Violaceae, with around 400–500 species distributed around the world. Most species are found in the temperate Northern Hemisphere, however viola species (commonly called violets, pansies or heartsease) are also found in widely divergent areas such as Hawaii, Australasia, and the Andes in.
- Arborescent Arborescent is a term used by the French thinkers Deleuze and Guattari to characterize thinking marked by insistence on totalizing principles, binarism and dualism. The term, first used in A Thousand Plateaus where it was opposed to the rhizome, comes from the way genealogy trees are drawn: unidirectional progress, with no possible retroactivity - tree like with woody stems normally with a single trunk.
- Bud In botany, a bud is an undeveloped or embryonic shoot and normally occurs in the axil of a leaf or at the tip of the stem. Once formed, a bud may remain for some time in a dormant condition, or it may form a shoot immediately - an embryonic shoot with immature stem tip.
- Bulb A bulb is an underground vertical shoot that has modified leaves that are used as food storage organs by a dormant plant - a short vertical underground stem with fleshy storage leaves attached, e.g. onion Onion is a term used for many plants in the genus Allium. They are known by the common name "onion" but, used without qualifiers, it usually refers to Allium cepa. Allium cepa is also known as the "garden onion" or "bulb" onion. It is grown underground by the plant as a vertical shoot that is used for food storage,, daffodil Narcissus is the botanic name for a genus of mainly hardy, mostly spring-flowering, bulbs in the Amaryllis family native to Europe, North Africa, and Asia. There are also several Narcissus species that bloom in the autumn. Though Hortus Third cites 26 wild species, Daffodils for North American Gardens cites between 50 and 100 including species, tulip A tulip is a perennial plant in the genus Tulipa, comprising about 150 bulbous species with showy flowers, in the family Liliaceae. The species native range includes southern Europe, north Africa, and Asia from Anatolia and Iran in the west to northeast of China. The centre of diversity of the genus is in the Pamir and Hindu Kush mountains and the. Bulbs often function in reproduction by splitting to form new bulbs or producing small new bulbs termed bulblets. Bulbs are a combination of stem and leaves so may better be considered as leaves because the leaves make up the greater part.
- Caespitose - when stems grow in a tangled mass or clump or in low growing mats.
- Cladophyll Cladophylls, cladodes or phylloclades are branches or portions of a stem that resemble leaves and replace them as the main photosynthetic organs of the plant – they are often flattened, but may be needle-like. Unlike true leaves they may bear buds, flowers and shoots, sometimes including further cladophylls - a flattened stem that appears leaf like and is specialized for photosynthesis, e.g. asparagus Asparagus officinalis is a flowering plant species in the genus Asparagus from which the vegetable known as asparagus is obtained. It is native to most of Europe, northern Africa and western Asia, and is now widely cultivated as a vegetable crop, cactus A cactus is any member of the plant family Cactaceae, native to the Americas (with one exception, Rhipsalis baccifera, which is native to parts of the Old World). They are often used as ornamental plants, and some are also crop plants for fodder, forage, fruits, cochineal, and other uses. Cactuses are part of the plant order Caryophyllales, which pads.
- Climbing Climbing is the activity of using one's hands and feet to ascend a steep object. It is done both for recreation (to reach an inaccessible place, or for its own enjoyment) and professionally, as part of activities such as maintenance of a structure, or military operations - stems that cling or wrap around other plants or structures.
- Corm A corm is a short, vertical, swollen underground plant stem that serves as a storage organ used by some plants to survive winter or other adverse conditions such as summer drought and heat . A corm consists of one or more internodes with at least one growing point, with protective leaves modified into skins or tunics. The thin tunic leaves are dry - a short enlarged underground, storage stem, e.g. taro Taro is a tropical plant grown primarily as a root vegetable for its edible corm, and secondarily as a leaf vegetable. It is considered a staple in Oceanic cultures. It is believed to have been one of the earliest cultivated plants. It is known by many names, including dasheen in the Caribbean and arrowroot in East Africa; it is one of several, crocus Crocus is a genus of perennial flowering plants, native to a large area from coastal and subalpine areas of central and southern Europe (including the islands of the Aegean), North Africa and the Middle East, across Central Asia to western China, gladiolus Gladiolus is a genus of perennial bulbous flowering plants in the iris family (Iridaceae). Sometimes called the sword lily, the most widely-used English common name for these plants is simply gladiolus (plural gladioli, gladioluses or sometimes gladiolas).
- Decumbent - stems that lie flat on the ground and turn upwards at the ends.
- Fruticose - stems that grow shrub like with woody like habit.
- Herbaceous A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground. A herbaceous plant may be annual, biennial or perennial - non woody, they die at the end of the growing season.
- Pseudostem - A false stem made of the rolled bases of leaves, which may be 2 or 3 m tall as in banana Banana is the common name for herbaceous plants of the genus Musa and for the fruit they produce. Bananas come in a variety of sizes and colors when ripe, including yellow, purple, and red. In popular culture and commerce, "banana" usually refers to soft, sweet "dessert" bananas. Bananas from a group of cultivars with firmer,
- Rhizome In botany, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes. Rhizomes may also be referred to as creeping rootstalks, or rootstocks - a horizontal underground stem that functions mainly in reproduction but also in storage, e.g. most ferns A fern is any one of a group of about 12,000 species of plants . Unlike mosses they have xylem and phloem . They have stems, leaves, and roots like other vascular plants. Ferns do not have either seeds or flowers (they reproduce via spores), iris Iris is a genus of between 200–300 species of flowering plants with showy flowers. It takes its name from the Greek word for a rainbow, referring to the wide variety of flower colors found among the many species. As well as being the scientific name, iris is also very widely used as a common name; for one thing, it refers to all Iris species,
- Runner (plant part) In biology, stolons are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external skeletons - a type of stolon, horizontally growing on top of the ground and rooting at the nodes, aids in reproduction. e.g. strawberry The garden strawberry is a common plant of the genus Fragaria which is cultivated worldwide for its fruit, the strawberry. The fruit is widely appreciated, mainly for its characteristic aroma but also for its bright red color, and it is consumed in large quantities—either fresh, or in prepared foods such as preserves, fruit juice, pies, ice, spider plant Spider plants have long narrow leaves that are 20–40 cm long and 5–20 mm (0.2–0.8 in) broad, which grow from a central rosette. At the spot where a leaf would normally develop a node, these plants will produce adventitious roots down into the soil, and new above ground shoots. It also produces branched stolons with small white flowers and.
- Scape - a stem that holds flowers that comes out of the ground and has no normal leaves. Hosta Hosta is a genus of about 23–45 species of lily-like plants native to northeast Asia. They were once classified in the family Liliaceae but are now included in the family Agavaceae by the Angiosperm Phylogeny Group. The scientific name is also used as the common name; in the past they were also sometimes called the Corfu Lily, the Day Lily, or, Lily The genus Lilium are herbaceous flowering plants growing from bulbs. Most species are native to the temperate northern hemisphere. They comprise a genus of about 110 species in the lily family, Iris Iris is a genus of between 200–300 species of flowering plants with showy flowers. It takes its name from the Greek word for a rainbow, referring to the wide variety of flower colors found among the many species. As well as being the scientific name, iris is also very widely used as a common name; for one thing, it refers to all Iris species,.
- Stolons In biology, stolons are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external skeletons - a horizontal stem that produces rooted plantlets at its nodes and ends, forming near the surface of the ground.
- Tree A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to 6 m; some authors set a minimum of 10 cm trunk diameter - a woody stem that is longer than 5 meters with a main trunk In botany, trunk refers to the main structural member of a tree that supports the branches and is supported by and directly attached to the roots. The trunk is covered by the bark, which is an important diagnostic feature in tree identification, and which often differs markedly from the bottom of the trunk to the top, depending on the species. The.
- Thorns Thorns, spines, and prickles are three types of structures that appear in plants which have a similar appearance, but which are derived from different plant organs. All three are hard structures with sharp, pointy ends, which are generally used by plants to protect themselves from herbivores - a reduced stem with a sharp point and rounded shape, used for protection against animals. e.g. honey locust The Honey locust is a deciduous tree native to eastern North America. It is mostly found in the moist soil of river valleys ranging from southeastern South Dakota to New Orleans and central Texas, and as far east as eastern Massachusetts, hawthorn Hawthorn is a large genus of shrubs and trees in the rose family, Rosaceae, native to temperate regions of the Northern Hemisphere in Europe, Asia and North America. It is the state flower of Missouri. The name hawthorn was originally applied to the species native to northern Europe, especially the Common Hawthorn C. monogyna, and the unmodified.
- Tuber Tubers are various types of modified plant structures that are enlarged to store nutrients. They are used by plants to survive the winter or dry months and provide energy and nutrients for regrowth during the next growing season and they are a means of asexual reproduction. Two different groups of tubers are: stem tubers, and root tubers - a swollen, underground storage stem adapted for storage and reproduction, e.g. potato The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species. Potatoes are the world's fourth largest food crop, following rice, wheat, and.
- Woody - hard textured stems with secondary xylem.
Stem structure
Flax Flax (binomial name: Linum usitatissimum) is a member of the genus Linum in the family Linaceae. It is native to the region extending from the eastern Mediterranean to India and was probably first domesticated in the Fertile Crescent. This is called as Agasi/Akshi in Kannada, Jawas/Javas (जवस) or Alashi (अळशी) in Marathi. Flax was stem cross-section, showing locations of underlying tissues. Ep = epidermis The epidermis is a single-layered group of cells that covers plants leaves, flowers, roots and stems. It forms a boundary between the plant and the external world. The epidermis serves several functions, it protects against water loss, regulates gas exchange, secretes metabolic compounds, and absorbs water and mineral nutrients. The epidermis of; C = cortex In botany, the cortex is the outer layer of the stem or root of a plant, bounded on the outside by the epidermis and on the inside by the endodermis. It is composed mostly of undifferentiated cells, usually large thin-walled parenchyma cells of the ground tissue system. The outer cortical cells often acquire irregularly thickened cell walls, and; BF = bast fibres; P = phloem; X = xylem; Pi = pith- See also: Stele (biology)
Stem usually consist of three tissues, dermal tissue, ground tissue and vascular tissue. The dermal tissue covers the outer surface of the stem and usually functions to waterproof, protect and control gas exchange. The ground tissue usually consists mainly of parenchyma cells and fills in around the vascular tissue. It sometimes functions in photosynthesis. Vascular tissue provides long distance transport and structural support. Most or all ground tissue may be lost in woody stems. The dermal tissue of aquatic plants stems may lack the waterproofing found in aerial stems. The arrangement of the vascular tissues varies widely among plant species.
Dicot stems
Dicot stems with primary growth have pith in the center, with vascular bundles forming a distinct ring visible when the stem is viewed in cross section. The outside of the stem is covered with an epidermis, which is covered by a waterproof cuticle. The epidermis also may contain stomata for gas exchange and multicellular stem hairs. A cortex consisting of Hypodermis (collenchyma cells) and Endodermis (starch containing cells)is present above the pericycle and vascular bundles.
Woody dicots and many nonwoody dicots have secondary growth originating from their lateral or secondary meristems: the vascular cambium and the cork cambium or phellogen. The vascular cambium forms between the xylem and phloem in the vascular bundles and connects to form a continuous cylinder. The vascular cambium cells divide to produce secondary xylem to the inside and secondary phloem to the outside. As the stem increases in diameter due to production of secondary xylem and secondary phloem, the cortex and epidermis are eventually destroyed. Before the cortex is destroyed, a cork cambium develops there. The cork cambium divides to produce waterproof cork cells externally and sometimes phelloderm cells internally. Those three tissues form the periderm, which replaces the epidermis in function. Areas of loosely-packed cells in the periderm that function in gas exchange are called lenticels.
Secondary xylem is commercially important as wood. The seasonal variation in growth from the vascular cambium is what creates yearly tree rings in temperate climates. Tree rings are the basis of dendrochronology, which dates wooden objects and associated artifacts. Dendroclimatology is the use of tree rings as a record of past climates. The aerial stem of an adult tree is called a trunk. The dead, usually darker inner wood of a large diameter trunk is termed the heartwood. The outer, living wood is termed the sapwood.
Monocot stems
Stems of two Roystonea regia palms showing characteristic bulge, leaf scars and fibrous roots, Kolkata, IndiaVascular bundles are present throughout the monocot stem, although concentrated towards the outside. This differs from the dicot stem that has a ring of vascular bundles and often none in the center. The shoot apex in monocot stems is more elongated. Leaf sheathes grow up around it, protecting it. This is true to some extent of almost all monocots. Monocots rarely produce secondary growth and are therefore seldom woody, with Palms being notable exceptions. However, many monocot stems increase in diameter via anamolous secondary growth.
Gymnosperm stems
The trunk of this redwood tree is its stem.All gymnosperms are woody plants. Their stems are similar in structure to woody dicots except that most gymnosperms produce only tracheids in their xylem, not the vessels found in dicots. Gymnosperm wood also often contains resin ducts. Woody dicots are called hardwoods, e.g. oak, maple and walnut. In contrast, softwoods are gymnosperms, such as pine, spruce and fir.
Tasmanian tree fernFern stems
Most ferns have rhizomes with no vertical stem. The exception is tree ferns, with vertical stems up to about 20 meters. The stem anatomy of ferns is more complicated than that of dicots because fern stems often have one or more leaf gaps in cross section. A leaf gap is where the vascular tissue branches off to a frond. In cross section, the vascular tissue does not form a complete cylinder where a leaf gap occurs. Fern stems may have solenosteles or dictyosteles or variations of them. Many fern stems have phloem tissue on both sides of the xylem in cross-section. .
Economic importance
White and green asparagus - crispy stems are the edible parts of this vegetableThere are thousands of species whose stems have economic uses. Stems provide a few major staple crops such as potato and taro. Sugarcane stems are a major source of sugar. Maple sugar is obtained from trunks of maple trees. Vegetables from stems are asparagus, bamboo shoots, cactus pads or nopalitos, kohlrabi, and water chestnut. The spice, cinnamon is bark from a tree trunk. Cellulose from tree trunks is a food additive in bread, grated Parmesan cheese, and other processed foods. Gum arabic is an important food additive obtained from the trunks of Acacia senegal trees. Chicle, the main ingredient in chewing gum, is obtained from trunks of the chicle tree.
Medicines obtained from stems include quinine from the bark of cinchona trees, camphor distilled from wood of a tree in the same genus that provides cinnamon, and the muscle relaxant curare from the bark of tropical vines.
Wood is a used in thousands of ways, e.g. buildings, furniture, boats, airplanes, wagons, car parts, musical instruments, sports equipment, railroad ties, utility poles, fence posts, pilings, toothpicks, matches, plywood, coffins, shingles, barrel staves, toys, tool handles, picture frames, veneer, charcoal and firewood. Wood pulp is widely used to make paper, cardboard, cellulose sponges, cellophane and some important plastics and textiles, such as cellulose acetate and rayon. Bamboo stems also have hundreds of uses, including paper, buildings, furniture, boats, musical instruments, fishing poles, water pipes, plant stakes, and scaffolding. Trunks of palm trees and tree ferns are often used for building. Reed stems are also important building materials in some areas.
Tannins used for tanning leather are obtained from the wood of certain trees, such as quebracho. Cork is obtained from the bark of the cork oak. Rubber is obtained from the trunks of Hevea brasiliensis. Rattan, used for furniture and baskets, is made from the stems of tropical vining palms. Bast fibers for textiles and rope are obtained from stems include flax, hemp, jute and ramie. The earliest paper was obtained from the stems of papyrus by the ancient Egyptians.
Amber is fossilized sap from tree trunks; it is used for jewelry and may contain ancient animals. Resins from conifer wood are used to produce turpentine and rosin. Tree bark is often used as a mulch and in growing media for container plants.
Some ornamental plants are grown mainly for their attractive stems, e.g.:
- White bark of paper birch
- Twisted branches of corkscrew willow and Harry Lauder's walking stick (Corylus avellana 'Contorta')
- Red, peeling bark of paperbark maple
References
- ^ Raven, Peter H., Ray Franklin Evert, and Helena Curtis. 1981. Biology of plants. New York, N.Y.: Worth Publishers.ISBN 0-87901-132-7
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Categories: Plant anatomy | Plant morphology
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