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30-513: Stem tubers manifest as thickened rhizomes (underground stems) or stolons (horizontal connections between organisms); examples include the potato and yam . The term root tuber describes modified lateral roots , as in sweet potatoes , cassava , and dahlias . The term originates from the Latin tuber , meaning 'lump, bump, or swelling'. Some writers limit the definition of tuber to structures derived from stems , while others also apply

60-452: A rhizome ( / ˈ r aɪ z oʊ m / RY -zohm ) is a modified subterranean plant stem that sends out roots and shoots from its nodes . Rhizomes are also called creeping rootstalks or just rootstalks . Rhizomes develop from axillary buds and grow horizontally. The rhizome also retains the ability to allow new shoots to grow upwards. A rhizome is the main stem of the plant that runs typically underground and horizontally to

90-459: A new fan that grows roots that produce thick tubers and then send out more stolons. Plants with root tubers can be propagated from late summer to late winter by digging up the tubers and separating them, making sure that each piece has some crown tissue for replanting. Root tubers are a rich source of nutrients for humans and wild animals, e.g. those of Sagittaria plants which are eaten by ducks. Rhizome In botany and dendrology ,

120-779: A seed treatment in order to stimulate the natural anti-pest defenses of the plants that germinate from the treated seeds. In this application jasmonates are sprayed onto plants that have already started growing. These applications stimulate the production of protease inhibitor in the plant. This production of protease inhibitor can protect the plant from insects, decreasing infestation rates and physical damage sustained due to herbivores. However, due to its antagonistic relationship with salicylic acid (an important signal in pathogen defense) in some plant species, it may result in an increased susceptibility to viral agents and other pathogens. In Zea mays , salicylic acid and JA are mediated by NPR1 (nonexpressor of pathogenesis-related genes1), which

150-657: A shoot that branches off a mature plant. The offspring or new tubers are attached to a parent tuber or form at the end of a hypogeogenous (initiated below ground) rhizome. In the autumn the plant dies, except for the new offspring tubers, which have one dominant bud that in spring regrows a new shoot producing stems and leaves; in summer the tubers decay and new tubers begin to grow. Some plants also form smaller tubers or tubercules that act like seeds, producing small plants that resemble (in morphology and size) seedlings. Some stem tubers are long-lived, such as those of tuberous begonias , but many plants have tubers that survive only until

180-466: A tuber is filled with starch stored in enlarged parenchyma -like cells. The inside of a tuber has the typical cell structures of any stem, including a pith, vascular zones, and a cortex. The tuber is produced in one growing season and used to perennate the plant and as a means of propagation . When fall comes, the above-ground structure of the plant dies, but the tubers survive underground over winter until spring, when they regenerate new shoots that use

210-461: Is an organic compound found in several plants including jasmine . The molecule is a member of the jasmonate class of plant hormones . It is biosynthesized from linolenic acid by the octadecanoid pathway . It was first isolated in 1957 as the methyl ester of jasmonic acid by the Swiss chemist Édouard Demole and his colleagues. Its biosynthesis starts from the fatty acid linolenic acid , which

240-427: Is essential in preventing herbivores from exploiting this antagonistic system. Armyworms ( Spodoptera caterpillars), through unknown mechanisms, are able to increase the activity of the salicylic acid pathway in maize, resulting in the depression of JA synthesis, but thanks to NPR1 mediation, JA levels aren't decreased by a significant amount. Jasmonic acid is also converted to a variety of derivatives including

270-473: Is oxygenated by lipoxygenase (13-LOX), forming a hydroperoxide . This peroxide then cyclizes in the presence of allene oxide synthase to form an allene oxide . The rearrangement of allene oxide to form 12-oxophytodienoic acid is catalyzed by the enzyme allene oxide cyclase . A series of β-oxidations results in 7-isojasmonic acid. In the absence of enzyme, this isojasmonic acid isomerizes to jasmonic acid. The major function of JA and its various metabolites

300-428: Is regulating plant responses to abiotic and biotic stresses as well as plant growth and development. Regulated plant growth and development processes include growth inhibition, senescence , tendril coiling, flower development and leaf abscission. JA is also responsible for tuber formation in potatoes and yams. It has an important role in response to wounding of plants and systemic acquired resistance . The Dgl gene

330-443: Is responsible for maintaining levels of JA during usual conditions in Zea mays as well as the preliminary release of jasmonic acid shortly after being fed upon. When plants are attacked by insects, they respond by releasing JA, which activates the expression of protease inhibitors , among many other anti-herbivore defense compounds. These protease inhibitors prevent proteolytic activity of

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360-452: The base of the stem, weighing up to 1.8 kg (3 lb 15 oz) per tuber, forming from axillary buds producing short stolons that grow into tubers. Even though legumes are not commonly associated with forming stem tubers, Lathyrus tuberosus is an example native to Asia and Europe, where it was once grown as a crop. Potatoes are stem tubers – enlarged stolons thicken to develop into storage organs . The tuber has all

390-420: The bottom from a basal section. Typically the tuber has an oblong rounded shape. Tuberous begonias, yams , and cyclamens are commonly grown stem tubers. Mignonette vine ( Anredera cordifolia ) produces aerial stem tubers on 3.5-to-7.5-metre-tall (12 to 25 ft) vines; the tubers fall to the ground and grow. Plectranthus esculentus , of the mint family Lamiaceae , produces tuberous underground organs from

420-492: The ends, they are often also called runners such as in the strawberry plant. A stem tuber is a thickened part of a rhizome or stolon that has been enlarged for use as a storage organ . In general, a tuber is high in starch , e.g. the potato , which is a modified stolon. The term "tuber" is often used imprecisely and is sometimes applied to plants with rhizomes. The plant uses the rhizome to store starches , proteins , and other nutrients. These nutrients become useful for

450-560: The green plant. A root tuber, tuberous root or storage root is a modified lateral root , enlarged to function as a storage organ . The enlarged area of the tuber can be produced at the end or middle of a root or involve the entire root. It is thus different in origin, but similar in function and appearance, to a stem tuber. Plants with tuberous roots include the sweet potato ( Ipomoea batatas ), cassava , dahlia , and Sagittaria (arrowhead) species. Root tubers are perennating organs, thickened roots that store nutrients over periods when

480-445: The growth of rhizomes, specifically in rhubarb . Ethylene that was applied externally was found to affect internal ethylene levels, allowing easy manipulations of ethylene concentrations. Knowledge of how to use these hormones to induce rhizome growth could help farmers and biologists to produce plants grown from rhizomes, and more easily cultivate and grow better plants. Some plants have rhizomes that grow above ground or that lie at

510-447: The insects' digestive proteases or "salivary proteins", thereby stopping them from acquiring the needed nitrogen in the protein for their own growth. JA also activates the expression of Polyphenol oxidase which promotes the production of quinolines . These can interfere with the insect's enzyme production and decrease the nutrition content of the ingested plant. JA may have a role in pest control. Indeed, JA has been considered as

540-492: The newly generated tubers; the next growing season, the tubers produce new shoots. As the shoots of the new plant grow, the stored reserves of the tuber are consumed in the production of new roots, stems, and reproductive organs; any remaining root tissue dies concurrently to the plant's regeneration of the next generation of tubers. Hemerocallis fulva (orange daylily) and a number of daylily hybrids have large root tubers; H. fulva spreads by underground stolons that end with

570-409: The parts of a normal stem, including nodes and internodes. The nodes are the eyes and each has a leaf scar. The nodes or eyes are arranged around the tuber in a spiral fashion beginning on the end opposite the attachment point to the stolon. The terminal bud is produced at the farthest point away from the stolon attachment and tubers, and thus show the same apical dominance as a normal stem. Internally,

600-416: The plant cannot actively grow, thus permitting survival from one year to the next. The massive enlargement of secondary roots typically represented by sweet potato have the internal and external cell and tissue structures of a normal root; they produce adventitious roots and stems, which again produce adventitious roots. In root tubers, there are no nodes and internodes or reduced leaves. The proximal end of

630-469: The plant when new shoots must be formed or when the plant dies back for the winter. If a rhizome is separated, each piece may be able to give rise to a new plant. This is a process known as vegetative reproduction and is used by farmers and gardeners to propagate certain plants. This also allows for lateral spread of grasses like bamboo and bunch grasses . Examples of plants that are propagated this way include hops , asparagus , ginger , irises, lily of

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660-400: The plants have fully leafed out, at which point the tuber is reduced to a shriveled-up husk. Stem tubers generally start off as enlargements of the hypocotyl section of a seedling, but sometimes also include the first node or two of the epicotyl and the upper section of the root. The tuber has a vertical orientation, with one or a few vegetative buds on the top and fibrous roots produced on

690-757: The soil surface, including some Iris species as well as ferns , whose spreading stems are rhizomes. Plants with underground rhizomes include gingers , bamboo , snake plant , the Venus flytrap , Chinese lantern , western poison-oak , hops, and Alstroemeria , and some grasses, such as Johnson grass , Bermuda grass , and purple nut sedge . Rhizomes generally form a single layer, but in giant horsetails , can be multi-tiered. Many rhizomes have culinary value, and some, such as zhe'ergen , are commonly consumed raw. Some rhizomes that are used directly in cooking include ginger, turmeric , galangal , fingerroot , and lotus . Jasmonic acid Jasmonic acid ( JA )

720-445: The soil surface. Rhizomes have nodes and internodes and auxiliary buds. Roots do not have nodes and internodes and have a root cap terminating their ends. In general, rhizomes have short internodes, send out roots from the bottom of the nodes, and generate new upward-growing shoots from the top of the nodes. A stolon is similar to a rhizome, but stolon sprouts from an existing stem having long internodes and generating new shoots at

750-424: The stolon must be a certain age. The enzyme lipoxygenase makes a hormone, jasmonic acid , which is involved in the control of potato tuber development. The stolons are easily recognized when potato plants are grown from seeds. As the plants grow, stolons are produced around the soil surface from the nodes. The tubers form close to the soil surface and sometimes even on top of the ground. When potatoes are cultivated,

780-404: The stored food in the tuber to grow. As the main shoot develops from the tuber, the base of the shoot close to the tuber produces adventitious roots and lateral buds on the shoot. The shoot also produces stolons that are long etiolated stems. The stolon elongates during long days with the presence of high auxins levels that prevent root growth off of the stolon. Before new tuber formation begins,

810-422: The term to structures derived from roots . A stem tuber forms from thickened rhizomes or stolons . The top sides of the tuber produce shoots that grow into typical stems and leaves and the undersides produce roots. They tend to form at the sides of the parent plant and are most often located near the soil surface. The underground tuber is normally a short-lived storage and regenerative organ developing from

840-412: The tuber, which was attached to the old plant, has crown tissue that produces buds which grow into new stems and foliage. The distal end of the tuber normally produces unmodified roots. In stem tubers the order is reversed, with the distal end producing stems. Tuberous roots are biennial in duration: the plant produces tubers the first year, and at the end of the growing season, the shoots often die, leaving

870-408: The tubers are cut into pieces and planted much deeper into the soil. Planting the pieces deeper creates more area for the plants to generate the tubers and their size increases. The pieces sprout shoots that grow to the surface. These shoots are rhizome-like and generate short stolons from the nodes while in the ground. When the shoots reach the soil surface, they produce roots and shoots that grow into

900-475: The valley , cannas , and sympodial orchids . Stored rhizomes are subject to bacterial and fungal infections , making them unsuitable for replanting and greatly diminishing stocks. However, rhizomes can also be produced artificially from tissue cultures . The ability to easily grow rhizomes from tissue cultures leads to better stocks for replanting and greater yields. The plant hormones ethylene and jasmonic acid have been found to help induce and regulate

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