In botany and dendrology, a rhizome is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are called creeping rootstalks or just rootstalks. Rhizomes grow horizontally; the rhizome retains the ability to allow new shoots to grow upwards. A rhizome is the main stem of the plant. A stolon is similar to a rhizome, but a stolon sprouts from an existing stem, has long internodes, generates new shoots at the end, such as in the strawberry plant. In general, rhizomes have short internodes, send out roots from the bottom of the nodes, generate new upward-growing shoots from the top of the nodes. A stem tuber is a thickened part of a rhizome or stolon, enlarged for use as a storage organ. In general, a tuber is high in starch, e.g. the potato, a modified stolon. The term "tuber" is used imprecisely and is sometimes applied to plants with rhizomes. If a rhizome is separated each piece may be able to give rise to a new plant; the plant uses the rhizome to store starches and other nutrients.
These nutrients become useful for the plant when new shoots must be formed or when the plant dies back for the winter. This is a process known as vegetative reproduction and is used by farmers and gardeners to propagate certain plants; this allows for lateral spread of grasses like bamboo and bunch grasses. Examples of plants that are propagated this way include hops, ginger, lily of the valley and sympodial orchids; some rhizomes which are used directly in cooking include ginger, galangal and lotus. Stored rhizomes are subject to bacterial and fungal infections, making them unsuitable for replanting and diminishing stocks. However, rhizomes can be produced artificially from tissue cultures; the ability to 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 the growth of rhizomes in rhubarb. Ethylene, 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 producing plants grown from rhizomes more cultivate and grow better plants. Some plants have rhizomes that grow above ground or that lie at the soil surface, including some Iris species, ferns, whose spreading stems are rhizomes. Plants with underground rhizomes include gingers, the Venus flytrap, Chinese lantern, western poison-oak and Alstroemeria, the weeds Johnson grass, Bermuda grass, purple nut sedge. Rhizomes form a single layer, but in giant horsetails, can be multi-tiered. Many rhizomes have culinary value, some, such as zhe'ergen, are consumed raw. Aspen Corm Mycorrhiza Media related to Rhizomes at Wikimedia Commons The Rhizome Collective for sustainable living
The Enron scandal, publicized in October 2001 led to the bankruptcy of the Enron Corporation, an American energy company based in Houston and the de facto dissolution of Arthur Andersen, one of the five largest audit and accountancy partnerships in the world. In addition to being the largest bankruptcy reorganization in American history at that time, Enron was cited as the biggest audit failure. Enron was formed in 1985 by Kenneth Lay after merging InterNorth. Several years when Jeffrey Skilling was hired, he developed a staff of executives that – by the use of accounting loopholes, special purpose entities, poor financial reporting – were able to hide billions of dollars in debt from failed deals and projects. Chief Financial Officer Andrew Fastow and other executives not only misled Enron's Board of Directors and Audit Committee on high-risk accounting practices, but pressured Arthur Andersen to ignore the issues. Enron shareholders filed a $40 billion lawsuit after the company's stock price, which achieved a high of US$90.75 per share in mid-2000, plummeted to less than $1 by the end of November 2001.
The U. S. Securities and Exchange Commission began an investigation, rival Houston competitor Dynegy offered to purchase the company at a low price; the deal failed, on December 2, 2001, Enron filed for bankruptcy under Chapter 11 of the United States Bankruptcy Code. Enron's $63.4 billion in assets made it the largest corporate bankruptcy in U. S. history until WorldCom's bankruptcy the next year. Many executives at Enron were indicted for a variety of charges and some were sentenced to prison. Andersen was found guilty of illegally destroying documents relevant to the SEC investigation, which voided its license to audit public companies and closed the firm. By the time the ruling was overturned at the U. S. Supreme Court, the company had ceased operating. Enron employees and shareholders received limited returns in lawsuits, despite losing billions in pensions and stock prices; as a consequence of the scandal, new regulations and legislation were enacted to expand the accuracy of financial reporting for public companies.
One piece of legislation, the Sarbanes–Oxley Act, increased penalties for destroying, altering, or fabricating records in federal investigations or for attempting to defraud shareholders. The act increased the accountability of auditing firms to remain unbiased and independent of their clients. In 1985, Kenneth Lay merged the natural gas pipeline companies of Houston Natural Gas and InterNorth to form Enron. In the early 1990s, he helped to initiate the selling of electricity at market prices, soon after, Congress approved legislation deregulating the sale of natural gas; the resulting markets made it possible for traders such as Enron to sell energy at higher prices, thereby increasing its revenue. After producers and local governments decried the resultant price volatility and asked for increased regulation, strong lobbying on the part of Enron and others prevented such regulation; as Enron became the largest seller of natural gas in North America by 1992, its trading of gas contracts earned $122 million, the second largest contributor to the company's net income.
The November 1999 creation of the EnronOnline trading website allowed the company to better manage its contracts trading business. In an attempt to achieve further growth, Enron pursued a diversification strategy; the company owned and operated a variety of assets including gas pipelines, electricity plants and paper plants, water plants, broadband services across the globe. The corporation gained additional revenue by trading contracts for the same array of products and services with which it was involved; this included setting up power generation plants in developing countries and emerging markets including The Philippines and India. Enron's stock increased from the start of the 1990s until year-end 1998 by 311%, only modestly higher than the average rate of growth in the Standard & Poor 500 index. However, the stock increased by 56% in 1999 and a further 87% in 2000, compared to a 20% increase and a 10% decrease for the index during the same years. By December 31, 2000, Enron's stock was priced at $83.13 and its market capitalization exceeded $60 billion, 70 times earnings and six times book value, an indication of the stock market's high expectations about its future prospects.
In addition, Enron was rated the most innovative large company in America in Fortune's Most Admired Companies survey. Enron's complex financial statements were confusing to analysts. In addition, its complex business model and unethical practices required that the company use accounting limitations to misrepresent earnings and modify the balance sheet to indicate favorable performance; the combination of these issues resulted in the bankruptcy of the company, the majority of them were perpetuated by the indirect knowledge or direct actions of Lay, Jeffrey Skilling, Andrew Fastow, other executives such as Rebecca Mark. Lay served as the chairman of the company in its last few years, approved of the actions of Skilling and Fastow, although he did not always inquire about the details. Skilling focused on meeting Wall Street expectations, advocated the use of mark-to-market accounting and pressured Enron executives to find new ways to hide its debt. Fastow and other executives "created off-balance-sheet vehicles, complex financing structures, deals so bewildering that few people could understand them."
Enron and other energy suppliers earned profits by providing services such as wholesale tr
A stem is one of two main structural axes of a vascular plant, the other being the root. The stem is divided into nodes and internodes: The nodes hold one or more leaves, as well as buds which can grow into branches. Adventitious roots may be produced from the nodes; the internodes distance one node from another. The term "shoots" is confused with "stems". In most plants stems are located above the soil surface but some plants have underground stems. Stems have four main functions which are: Support for and the elevation of leaves and fruits; 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 and phloem Storage of nutrients Production of new living tissue; the normal lifespan of plant cells is one to three years. Stems have cells called meristems. Stems are specialized for storage, asexual reproduction, protection or photosynthesis, including the following: Acaulescent – used to describe stems in plants that appear to be stemless.
These stems are just short, the leaves appearing to rise directly out of the ground, e.g. some Viola species. Arborescent – tree like with woody stems with a single trunk. Axillary bud – a bud which grows at the point of attachment of an older leaf with the stem, it gives rise to a shoot. Branched – aerial stems are described as being branched or unbranched Bud – an embryonic shoot with immature stem tip. Bulb – a short vertical underground stem with fleshy storage leaves attached, e.g. onion, tulip. Bulbs 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. Cladode – a flattened stem that appears more-or-less leaf like and is specialized for photosynthesis, e.g. cactus pads. Climbing -- stems that wrap around other plants or structures. Corm – a short enlarged underground, storage stem, e.g. taro, gladiolus.
Decumbent -- stems that lie flat on the turn upwards at the ends. Fruticose -- stems. Herbaceous – non woody, they die at the end of the growing season. Internode – an interval between two successive nodes, it possesses the ability to elongate, either from its base or from its extremity depending on the species. Node – a point of attachment of a leaf or a twig on the stem in seed plants. A node is a small growth zone. Pedicel – stems that serve as the stalk of an individual flower in an inflorescence or infrutescence. Peduncle – a stem that supports an inflorescence Prickle – a sharpened extension of the stem's outer layers, e.g. roses. Pseudostem – a false stem made of the rolled bases of leaves, which may be 2 or 3 m tall as in banana Rhizome – a horizontal underground stem that functions in reproduction but in storage, e.g. most ferns, iris Runner – a type of stolon, horizontally growing on top of the ground and rooting at the nodes, aids in reproduction. E.g. garden strawberry, Chlorophytum comosum.
Scape – a stem that holds flowers that comes out of the ground and has no normal leaves. Hosta, Iris, Garlic. Stolon – a horizontal stem that produces rooted plantlets at its nodes and ends, forming near the surface of the ground. Thorn – a modified stem with a sharpened point. Tuber – a swollen, underground storage stem adapted for storage and reproduction, e.g. potato. Woody – hard textured stems with secondary xylem. Stem consist of three tissues, dermal tissue, ground tissue and vascular tissue; the dermal tissue covers the outer surface of the stem and functions to waterproof and control gas exchange. The ground tissue consists of parenchyma cells and fills in around the vascular tissue, it sometimes functions in photosynthesis. Vascular tissue provides structural support. Most or all ground tissue may be lost in woody stems; the dermal tissue of aquatic plants stems. The arrangement of the vascular tissues varies 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, covered by a waterproof cuticle. The epidermis may contain stomata for gas exchange and multicellular stem hairs called trichomes. A cortex consisting of hypodermis and endodermis 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 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.
Areas of loosely pack
In vascular plants, the root is the organ of a plant that lies below the surface of the soil. Roots can be aerial or aerating, that is, growing up above the ground or above water. Furthermore, a stem occurring below ground is not exceptional either. Therefore, the root is best defined as the non-nodes bearing parts of the plant's body. However, important internal structural differences between stems and roots exist; the fossil record of roots—or rather, infilled voids where roots rotted after death—spans back to the late Silurian, about 430 million years ago. Their identification is difficult, because casts and molds of roots are so similar in appearance to animal burrows, they can be discriminated using a range of features. The first root that comes from a plant is called the radicle. A root's four major functions are: absorption of inorganic nutrients. In response to the concentration of nutrients, roots synthesise cytokinin, which acts as a signal as to how fast the shoots can grow. Roots function in storage of food and nutrients.
The roots of most vascular plant species enter into symbiosis with certain fungi to form mycorrhizae, a large range of other organisms including bacteria closely associate with roots. When dissected, the arrangement of the cells in a root is root hair, epiblem, endodermis, pericycle and, the vascular tissue in the centre of a root to transport the water absorbed by the root to other places of the plant; the most striking characteristic of roots is that, roots have an endogenous origin, i.e. it originates and develops from an inner layer of the mother axis. Whereas Stem-branching and leaves are exogenous, i.e. start to develop from the cortex, an outer layer. In its simplest form, the term root architecture refers to the spatial configuration of a plant’s root system; this system can be complex and is dependent upon multiple factors such as the species of the plant itself, the composition of the soil and the availability of nutrients. The configuration of root systems serves to structurally support the plant, compete with other plants and for uptake of nutrients from the soil.
Roots grow to specific conditions. For example, a root system that has developed in dry soil may not be as efficient in flooded soil, yet plants are able to adapt to other changes in the environment, such as seasonal changes. Root architecture plays the important role of providing a secure supply of nutrients and water as well as anchorage and support; the main terms used to classify the architecture of a root system are: Branch magnitude: the number of links. Topology: the pattern of branching, including:Herringbone: alternate lateral branching off a parent root Dichotomous: opposite, forked branches Radial: whorl of branches around a rootLink length: the distance between branches. Root angle: the radial angle of a lateral root’s base around the parent root’s circumference, the angle of a lateral root from its parent root, the angle an entire system spreads. Link radius: the diameter of a root. All components of the root architecture are regulated through a complex interaction between genetic responses and responses due to environmental stimuli.
These developmental stimuli are categorised as intrinsic, the genetic and nutritional influences, or extrinsic, the environmental influences and are interpreted by signal transduction pathways. The extrinsic factors that affect root architecture include gravity, light exposure and oxygen, as well as the availability or lack of nitrogen, sulphur and sodium chloride; the main hormones and respective pathways responsible for root architecture development include: Auxin – Auxin promotes root initiation, root emergence and primary root elongation. Cytokinins – Cytokinins regulate root apical meristem size and promote lateral root elongation. Gibberellins -- Together with ethylene they promote elongation. Together with auxin they promote root elongation. Gibberellins inhibit lateral root primordia initiation. Ethylene – Ethylene promotes crown root formation. Early root growth is one of the functions of the apical meristem located near the tip of the root; the meristem cells more or less continuously divide, producing more meristem, root cap cells, undifferentiated root cells.
The latter become the primary tissues of the root, first undergoing elongation, a process that pushes the root tip forward in the growing medium. These cells differentiate and mature into specialized cells of the root tissues. Growth from apical meristems is known as primary growth. Secondary growth encompasses all growth in diameter, a major component of woody plant tissues and many nonwoody plants. For example, storage roots of sweet potato are not woody. Secondary growth occurs at the lateral meristems, namely the vascular cork cambium; the former forms secondary phloem, while the latter forms the periderm. In plants with secondary growth, the vascular cambium, originating between the xylem and the phloem, forms a cylinder of tissue along the stem and root; the vascular cambium forms new cells on both the inside and outside of the cambium cylinder, with those on the inside forming secondary xylem cells, those on the outside forming secondary phloem cells. As