Misplaced Pages

#63936

24-439: Cormophytes ( Cormophyta ) is a historical term seldom used today for the plants that are differentiated into roots, stems and leaves . These plants differ from thallophytes , whose body is referred to as the thallus , i.e. a simple body not differentiated into leaves and stems. Definitions have varied, notably about whether mosses and liverworts are included. Stephan Endlicher , a 19th-century Austrian botanist , divided

48-430: 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. Gum arabic is an important food additive obtained from the trunks of Acacia senegal trees. Chicle ,

72-423: 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

96-627: Is the ancestral case, or they have an "anomalous secondary growth" of some type, or, in the case of palms, they enlarge their diameter in what is called a sort of secondary growth or not depending on the definition given to the term. Palm trees increase their trunk diameter due to division and enlargement of parenchyma cells, which is termed "primary gigantism" because there is no production of secondary xylem and phloem tissues, or sometimes "diffuse secondary growth". In some other monocot stems as in Yucca and Dracaena with anomalous secondary growth,

120-449: Is the growth that results from cell division in the cambia or lateral meristems and that causes the stems and roots to thicken, while primary growth is growth that occurs as a result of cell division at the tips of stems and roots, causing them to elongate, and gives rise to primary tissue. Secondary growth occurs in most seed plants , but monocots usually lack secondary growth. If they do have secondary growth, it differs from

144-401: Is the result of the activity of the two lateral meristems, the cork cambium and vascular cambium . Arising from lateral meristems, secondary growth increases the width of the plant root or stem, rather than its length. As long as the lateral meristems continue to produce new cells, the stem or root will continue to grow in diameter. In woody plants , this process produces wood , and shapes

168-399: 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 and is the result of tylosis . The outer, living wood is termed the sapwood. Vascular bundles are present throughout the monocot stem, although concentrated towards the outside. This differs from

192-408: Is to distribute food from photosynthetic tissue to other tissues. The two tissues are separated by cambium , a tissue that divides to form xylem or phloem cells. Stems are often specialized for storage, asexual reproduction, protection, or photosynthesis , including the following: Stem usually consist of three tissues: dermal tissue , ground tissue , and vascular tissue . Dermal tissue covers

216-486: 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. Foreign chemicals such as air pollutants, herbicides and pesticides can damage stem structures. There are thousands of species whose stems have economic uses. Stems provide

240-552: Is widely used to make paper , paperboard , cellulose sponges, cellophane and some important plastics and textiles , such as cellulose acetate and rayon . Bamboo stems also have hundreds of uses, including in paper, buildings, furniture, boats, musical instruments, fishing poles , water pipes , plant stakes, and scaffolding . Trunks of palms and tree ferns are often used for building. Stems of reed are an important building material for use in thatching in some areas. Tannins used for tanning leather are obtained from

264-606: 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 and bamboo being notable exceptions. However, many monocot stems increase in diameter via anomalous secondary growth. 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

SECTION 10

#1732781043064

288-415: 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

312-424: 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

336-716: 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 used in thousands of ways; it can be used to create 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

360-777: The outer surface of the stem and usually functions to protect the stem tissue, and control gas exchange . The predominant cells of dermal tissue are epidermal cells . Ground tissue usually consists mainly of parenchyma , collenchyma and sclerenchyma cells ; and they surround vascular tissue. Ground tissue is important in aiding metabolic activities (eg. respiration , photosynthesis , transport, storage) as well as acting as structural support and forming new meristems . Most or all ground tissue may be lost in woody stems . Vascular tissue, consisting of xylem , phloem and cambium ; provides long distance transport of water , minerals and metabolites ( sugars , amino acids ); whilst aiding structural support and growth. The arrangement of

384-532: The pattern of a single vascular cambium producing xylem to the inside and phloem to the outside as in ancestral lignophytes. Some dicots have anomalous secondary growth, e.g. in Bougainvillea a series of cambia arise outside the oldest phloem. Ancestral monocots lost their secondary growth and their stele has changed in a way it could not be recovered without major changes that are very unlikely to occur. Monocots either have no secondary growth, as

408-691: The plant into a tree with a thickened trunk. Because this growth usually ruptures the epidermis of the stem or roots, plants with secondary growth usually also develop a cork cambium . The cork cambium gives rise to thickened cork cells to protect the surface of the plant and reduce water loss. If this is kept up over many years, this process may produce a layer of cork. In the case of the cork oak it will yield harvestable cork . Secondary growth also occurs in many nonwoody plants, e.g. tomato , potato tuber , carrot taproot and sweet potato tuberous root . A few long-lived leaves also have secondary growth. Abnormal secondary growth does not follow

432-453: The soil surface, but some plants have underground stems . Stems have several main functions: Stems have two pipe-like tissues called xylem and phloem . The xylem tissue arises from the cell facing inside and transports water by the action of transpiration pull , capillary action , and root pressure . The phloem tissue arises from the cell facing outside and consists of sieve tubes and their companion cells. The function of phloem tissue

456-497: The stems of papyrus by the ancient Egyptians. Amber is fossilized sap from tree trunks; it is used for jewelry and may contain preserved 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. It also can become the natural habitat of lichens . Some ornamental plants are grown mainly for their attractive stems, e.g.: Secondary growth In botany , secondary growth

480-518: The typical pattern of other seed plants. The formation of secondary vascular tissues from the cambium is a characteristic feature of dicotyledons and gymnosperms . In certain monocots, the vascular tissues are also increased after the primary growth is completed but the cambium of these plants is of a different nature. In the living pteridophytes this feature is extremely rare, only occurring in Isoetes . In many vascular plants , secondary growth

504-519: The vascular tissues varies widely among plant species . 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 called trichomes . A cortex consisting of hypodermis (collenchyma cells) and endodermis (starch containing cells)

SECTION 20

#1732781043064

528-578: The vegetable kingdom in 1836 into two groups: the thallophytes were only the algae, lichens and fungi, and the cormophytes were the mosses, liverworts, ferns, Equisitaceae, club mosses and seed plants. This botany article is a stub . You can help Misplaced Pages by expanding it . Plant stem The stem is normally divided into nodes and internodes: The term " shoots " is often confused with "stems"; "shoots" generally refers to new fresh plant growth, including both stems and other structures like leaves or flowers. In most plants, stems are located above

552-519: 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 . Most ferns have rhizomes with no vertical stem. The exception is tree ferns , which have vertical stems that can grow up to about 20 metres. 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

576-408: 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 of plants like flax , hemp , jute and ramie . The earliest known paper was obtained from

#63936