Underground stem

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Underground stems are modified plants that derive from stem tissue but exist under the soil surface. [1] They function as storage tissues for food and nutrients, propagation of new clones, and perennation (survival from one growing season to the next). [2] Types include bulbs, corms, rhizomes, stolons, spindle-shaped[ citation needed ], and tubers.

Contents

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 which are called roots. The roots are modified to have root hairs and branch indiscriminately with cells that take in water and nutrients, while the stems are modified to move water and nutrients to and from the leaves and flowers. Stems have nodes with buds where leaves and flowers arise at specific locations, while roots do not. Plants use under ground stems to multiply their numbers by asexual reproduction and to survive from one year to the next, usually over a period of dormancy. [3] Some plants produce stems modified to store energy and preserve a location of potential growth to survive a cold or dry period which normally is a period of inactive growth, and when that period is over the plants resume new growth from the underground stems. [4] Being underground protects the stems from the elements during the dormancy period, such as freezing and thawing in winter or extreme heat and drought in summer or fire. They can also protect plants from heavy grazing pressure from animals, the plant might be eaten to the ground but new growth can occur from below ground stem that can not be reached by the herbivores. A number of plants, including weedy species, use underground stems to spread and colonize large areas, since the stems do not have to be supported or strong, less energy and resources are needed to produce these stems and often these plants have more mass under ground than above ground.

Types of underground stems

Different forms of underground stems include: [5]

A number of underground stems are consumed by people including; onion, potato, ginger, yam and taro.

Geophyte

A geophyte (earth+plant) is a plant with an underground storage organ including true bulbs, corms, tubers, tuberous roots, enlarged hypocotyls, and rhizomes. Most plants with underground stems are geophytes but not all plants that are geophytes have underground stems. Geophytes are often physiologically active even when they lack leaves. They are able to survive during adverse environmental conditions by going into a state of quiesce and later resume growth from their storage organs, which contain reserves of carbohydrates and water, when the environmental conditions are favorable again.

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Bulb A short plant stem with fleshy leaves or leaf bases for food storage.

In botany, a bulb is structurally a short stem with fleshy leaves or leaf bases that function as food storage organs during dormancy.

Root Part of a plant

In vascular plants, the roots are the organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They most often lie below the surface of the soil, but roots can also be aerial or aerating, that is, growing up above the ground or especially above water.

Tuber Enlarged structures in some plant species used as storage organs for nutrients

Tubers are enlarged structures in some plant species used as storage organs for nutrients. They are used for the plant's perennation, to provide energy and nutrients for regrowth during the next growing season, and as a means of asexual reproduction. Stem tubers form thickened rhizomes or stolons. Common plant species with stem tubers include the potato and yam. Some sources also treat modified lateral roots under the definition; these are found in sweet potatoes, cassava, and dahlias.

Rhizome Underground stem in which various plants asexualy reproduce via budding.

In botany and dendrology, a rhizome 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.

Pseudobulb

The pseudobulb is a storage organ found in many epiphytic and terrestrial sympodial orchids. It is derived from a thickening of the part of a stem between leaf nodes and may be composed of just one internode or several, termed heteroblastic and homoblastic respectively. All leaves and inflorescences usually arise from this structure. Pseudobulbs formed from a single internode produce the leaves and inflorescence from the top, while those that are formed from several internodes can possess leaves along its length. The modified sheath leaves that appear at the base of a pseudobulb and often enfold all or part of it are usually dry and papery, though in some orchids the sheaths bear leaf blades and the leaves at the pseudobulb's apex are reduced to scales.

Herbaceous plant Plant which has no persistent woody stem above ground

Herbaceous plants are vascular plants that have no persistent woody stems above ground, including many perennials, and nearly all annuals and biennials. Herbaceous plants include graminoids, forbs, and ferns. Forbs are generally defined as herbaceous broad leafed plants, while graminoids are plants with grass-like appearance including the true grasses, sedges, and rushes. In botany, the term "herbaceous plants" is often shortened to "herbs", but this word has also other meanings in cooking, medicine, and other fields.

Vegetative reproduction

Vegetative reproduction is any form of asexual reproduction occurring in plants in which a new plant grows from a fragment of the parent plant or a specialized reproductive structure.

Corm Plant stem

A corm, bulbo-tuber, or bulbotuber is a short, vertical, swollen underground plant stem that serves as a storage organ that some plants use to survive winter or other adverse conditions such as summer drought and heat (perennation).

Plant propagation Process in growing new plants from a variety of sources

Plant propagation is the process which grows new plants from a variety of sources: seeds, cuttings, and other plant parts. Plant propagation can also refer to the man-made or natural dispersal of seeds.

Clonal colony

A clonal colony or genet is a group of genetically identical individuals, such as plants, fungi, or bacteria, that have grown in a given location, all originating vegetatively, not sexually, from a single ancestor. In plants, an individual in such a population is referred to as a ramet. In fungi, "individuals" typically refers to the visible fruiting bodies or mushrooms that develop from a common mycelium which, although spread over a large area, is otherwise hidden in the soil. Clonal colonies are common in many plant species. Although many plants reproduce sexually through the production of seed, reproduction occurs by underground stolons or rhizomes in some plants. Above ground, these plants most often appear to be distinct individuals, but underground they remain interconnected and are all clones of the same plant. However, it is not always easy to recognize a clonal colony especially if it spreads underground and is also sexually reproducing.

A storage organ is a part of a plant specifically modified for storage of energy (generally in the form of carbohydrates) or water. Storage organs often grow underground, where they are better protected from attack by herbivores. Plants that have an underground storage organ are called geophytes in the Raunkiær plant life-form classification system. Storage organs often, but not always, act as perennating organs which enable plants to survive adverse conditions.

Stolon

In biology, stolons, also known as runners, are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external skeletons.

Raunkiær plant life-form Types of plant form as defined by Christen Raunkiær

The Raunkiær system is a system for categorizing plants using life-form categories, devised by Danish botanist Christen C. Raunkiær and later extended by various authors.

Edible plant stems are one part of plants that are eaten by humans. Most plants are made up of stems, roots, leaves, flowers, and produce fruits containing seeds. Humans most commonly eat the seeds, fruit, flowers, leaves, roots, and stems of many plants. There are also a few edible petioles such as celery or rhubarb.

Plant reproduction is the production of new offspring in plants, which can be accomplished by sexual or asexual reproduction. Sexual reproduction produces offspring by the fusion of gametes, resulting in offspring genetically different from the parent or parents. Asexual reproduction produces new individuals without the fusion of gametes, genetically identical to the parent plants and each other, except when mutations occur.

This page provides a glossary of plant morphology. Botanists and other biologists who study plant morphology use a number of different terms to classify and identify plant organs and parts that can be observed using no more than a handheld magnifying lens. This page provides help in understanding the numerous other pages describing plants by their various taxa. The accompanying page—Plant morphology—provides an overview of the science of the external form of plants. There is also an alphabetical list: Glossary of botanical terms. In contrast, this page deals with botanical terms in a systematic manner, with some illustrations, and organized by plant anatomy and function in plant physiology.

The laimosphere is the microbiologically enriched zone of soil that surrounds below-ground portions of plant stems; the laimosphere is analogous to the rhizosphere and spermosphere. The combining form laim- from laimos denotes a connecting organ (neck) while -sphere indicates a zone of influence. Topographically, the laimosphere includes the soil around any portion of subterranean plant organs other than roots where exuded nutrients stimulate microbial activities. Subterranean plant organs with a laimosphere include hypocotyls, epicotyls, stems, stolons, corms, bulbs, and leaves. Propagules of soil-borne plant pathogens, whose germination is stimulated by a plant exudates in the laimosphere, can initiate hypocotyl and stem rots leading to "damping-off". Pathogens commonly found to cause such diseases are species of Fusarium, Phoma, Phytophthora, Pythium, Rhizoctonia and Sclerotinia.

Plant stem structural axis of a vascular plant

A stem is one of two main structural axes of a vascular plant, the other being the root. It supports leaves, flowers and fruits, transports water and dissolved substances between the roots and the shoots in the xylem and phloem, stores nutrients, and produces new living tissue.

Succulent plant

In botany, succulent plants, also known as succulents, are plants with parts that are thickened, fleshy, and engorged, usually to retain water in arid climates or soil conditions. It is a characteristic that is not used scientifically for the definition of most families and genera of plants because it often can be used as an accurate characteristic only at the single species level. The word succulent comes from the Latin word sucus, meaning 'juice', or 'sap'. Succulent plants may store water in various structures, such as leaves and stems. Some definitions also include roots, thus geophytes that survive unfavorable periods by dying back to underground storage organs may be regarded as succulents. In horticultural use, the term succulent is sometimes used in a way that excludes plants that botanists would regard as succulents, such as cacti. Succulents are often grown as ornamental plants because of their striking and unusual appearance, as well as their ability to thrive with relatively minimal care.

Ornamental bulbous plant

Ornamental bulbous plants, often called ornamental bulbs or just bulbs in gardening and horticulture, are herbaceous perennials grown for ornamental purposes, which have underground or near ground storage organs. Botanists distinguish between true bulbs, corms, rhizomes, tubers and tuberous roots, any of which may be termed "bulbs" in horticulture. Bulb species usually lose their upper parts during adverse conditions such as summer drought and heat or winter cold. The bulb's storage organs contain moisture and nutrients that are used to survive these adverse conditions in a dormant state. When conditions become favourable the reserves sustain a new growth cycle. In addition, bulbs permit vegetative or asexual multiplication in these species. Ornamental bulbs are used in parks and gardens and as cut flowers.

References

  1. QA International Collectif (2007). The Visual Guide to Understanding Plants & the Vegetable Kingdom - Plants & the Vegetable Kingdom. Québec Amerique. pp. 35–. ISBN   978-2-7644-0894-0.
  2. V. B. Rastogi (1 January 1997). Modern Biology. Pitambar Publishing. pp. 22–. ISBN   978-81-209-0442-2.
  3. Ralph Persad (1 May 1994). Agricultural Science for the Caribbean. Nelson Thornes. pp. 26–. ISBN   978-0-17-566394-1.
  4. Linda Berg (23 March 2007). Introductory Botany: Plants, People, and the Environment, Media Edition. Cengage Learning. pp. 146–. ISBN   978-0-534-46669-5.
  5. Ray F. Evert; Susan E. Eichhorn; William A. Russin (22 April 2005). Laboratory Topics in Botany. W. H. Freeman. pp. 23–. ISBN   978-0-7167-6205-8.
  6. Marques, Isabel; Nieto Feliner, Gonzalo; Martins-Loução, Maria Amélia; Fuertes Aguilar, Javier (2011-11-01). "Fitness in Narcissus hybrids: low fertility is overcome by early hybrid vigour, absence of exogenous selection and high bulb propagation". Journal of Ecology. 99 (6): 1508–1519. doi: 10.1111/j.1365-2745.2011.01876.x . ISSN   1365-2745.