A desert is a barren area of land where little precipitation occurs and consequently living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to the processes of denudation, about one third of the land surface of the world is arid or semi-arid. This includes much of the regions where little precipitation occurs. Deserts can be classified by the amount of precipitation falls, by the temperature that prevails. Deserts are formed by weathering processes as large variations in temperature between day and night put strains on the rocks which consequently break in pieces, although rain seldom occurs in deserts, there are occasional downpours that can result in flash floods. Rain falling on hot rocks can cause them to shatter and the resulting fragments and this picks up particles of sand and dust and wafts them aloft in sand or dust storms. Wind-blown sand grains striking any solid object in their path can abrade the surface, rocks are smoothed down, and the wind sorts sand into uniform deposits.
The grains end up as level sheets of sand or are piled high in billowing sand dunes, other deserts are flat, stony plains where all the fine material has been blown away and the surface consists of a mosaic of smooth stones. These areas are known as desert pavements and little further erosion takes place, other desert features include rock outcrops, exposed bedrock and clays once deposited by flowing water. Temporary lakes may form and salt pans may be left when waters evaporate, there may be underground sources of water in the form of springs and seepages from aquifers. Where these are found, oases can occur and animals living in the desert need special adaptations to survive in the harsh environment. Plants tend to be tough and wiry with small or no leaves, water-resistant cuticles, some annual plants germinate and die in the course of a few weeks after rainfall while other long-lived plants survive for years and have deep root systems able to tap underground moisture. Animals need to cool and find enough food and water to survive.
Many are nocturnal and stay in the shade or underground during the heat of the day and they tend to be efficient at conserving water, extracting most of their needs from their food and concentrating their urine. Some animals remain in a state of dormancy for long periods and they reproduce rapidly while conditions are favorable before returning to dormancy. People have struggled to live in deserts and the surrounding lands for millennia. Nomads have moved their flocks and herds to wherever grazing is available, the cultivation of semi-arid regions encourages erosion of soil and is one of the causes of increased desertification. Many trade routes have been forged across deserts, especially across the Sahara Desert, large numbers of slaves were taken northwards across the Sahara
A vine in the narrowest sense is the grapevine, but more generally it can refer to any plant with a growth habit of trailing or scandent stems, lianas or runners. The word can refer to such stems or runners themselves, in the United Kingdom, the term vine applies almost exclusively to the grapevine. The term climber is used for all climbing plants, certain plants always grow as vines, while a few grow as vines only part of the time. For instance, poison ivy and bittersweet can grow as low shrubs when support is not available, a vine displays a growth form based on long stems. This has been a successful growth form for plants such as kudzu and Japanese honeysuckle. There are some tropical vines that develop skototropism, and grow away from the light, growth away from light allows the vine to reach a tree trunk, which it can climb to brighter regions. The vine growth form may enable plants to large areas quickly. This is the case with periwinkle and ground ivy and it is an adaptation to life in areas where small patches of fertile soil are adjacent to exposed areas with more sunlight but little or no soil. A vine can root in the soil but have most of its leaves in the brighter, exposed area, the evolution of a climbing habit has been implicated as a key innovation associated with the evolutionary success and diversification of a number of taxonomic groups of plants.
It has evolved independently in several plant families, using many different climbing methods such as and it directs its stem into a crevice in the bark of fibrous barked trees where the stem adopts a flattened profile and grows up the tree underneath the host trees outer bark. The fetterbush sends out branches that emerge near the top of the tree and these may be divided into woody vines or lianas, such as wisteria and common ivy, and herbaceous vines, such as morning glory. One odd group of vining plants is the fern genus Lygodium, the stem does not climb, but rather the fronds do. The fronds unroll from the tip, and theoretically never stop growing, they can form thickets as they unroll over other plants, gardeners can use the tendency of climbing plants to grow quickly. If a plant display is wanted quickly, a climber can achieve this, climbers can be trained over walls, fences, etc. Climbers can be grown over other plants to provide additional attraction, artificial support can be provided.
Some climbers climb by themselves, others need work, such as tying them in, vines widely differ in size and evolutionary origin. Darwin classified climbing groups based on their climbing method and he classified five classes of vines including twining plants, leaf climbers, tendril bearers, root climbers and hook climbers. Vines are unique in that they have multiple origins and a wide range of phenotypic plasticity
The bamboos /bæmˈbuː/ are evergreen perennial flowering plants in the subfamily Bambusoideae of the grass family Poaceae. The dicotyledonous woody xylem is absent, the absence of secondary growth wood causes the stems of monocots, including the palms and large bamboos, to be columnar rather than tapering. Bamboos include some of the plants in the world, due to a unique rhizome-dependent system. Certain species of bamboo can grow 91 cm within a 24-hour period, giant bamboos are the largest members of the grass family. Bamboos are of economic and cultural significance in South Asia, Southeast Asia and East Asia, being used for building materials, as a food source. Bamboo has a higher compressive strength than wood, brick, or concrete. The word bamboo comes from the Kannada term bambu, which was introduced to English through Indonesian, the subfamily in its current sense belongs to the BOP clade of grasses, where it is sister to the Pooideae. The woody bamboos do not form a group, instead. Altogether, more than 1,400 species are placed in 115 genera, most bamboo are native to warm and moist tropical and warm temperate climates.
However, many species are found in climates, from hot tropical regions to cool mountainous regions. In the Asia-Pacific region they occur across East Asia, from 50°N latitude in Sakhalin south to Northern Australia, and west to India, Japan, Korea and Australia, all have several endemic populations. They occur in numbers in sub-Saharan Africa, confined to tropical areas, from southern Senegal in the north to southern Mozambique. Bamboo is native through Central America and Mexico, northward into the Southeastern United States and continental Europe is not known to have any native species of bamboo. Recently, some attempts have been made to grow bamboo on a basis in the Great Lakes region of east-central Africa. In the United States, several companies are growing, bamboos include some of the fastest-growing plants on Earth, with reported growth rates up to 91 cm in 24 hours. Primarily growing in regions of warmer climates during the late Cretaceous period, some of the largest timber bamboo can grow over 30 m tall, and be as large as 25–30 cm in diameter.
However, the range for mature bamboo is species-dependent, with the smallest bamboos reaching only several inches high at maturity. A typical height range that would cover many of the common bamboos grown in the United States is 4. 6–12 m, depending on species
In botany, a bulb is structurally a short stem with fleshy leaves or leaf bases that function as food storage organs during dormancy. A bulbs leaf bases, known as scales, generally do not support leaves, at the center of the bulb is a vegetative growing point or an unexpanded flowering shoot. The base is formed by a stem, and plant growth occurs from this basal plate. Roots emerge from the underside of the base, and new stems, tunicate bulbs have dry, membranous outer scales that protect the continuous lamina of fleshy scales. Species in the genera Allium, Hippeastrum and Tulipa all have tunicate bulbs, non-tunicate bulbs, such as Lilium and Fritillaria species, lack the protective tunic and have looser scales. The technical term geophyte encompasses plants that form underground organs, including bulbs as well as tubers. Some epiphytic orchids form above-ground storage organs called pseudobulbs, that superficially resemble bulbs, nearly all plants that form true bulbs are monocotyledons, and include, Crinum, Hippeastrum and several other members of the amaryllis family Amaryllidaceae.
This includes onion and other alliums, members of the Amaryllid subfamily Allioideae, lily and many other members of the lily family Liliaceae. Two groups of Iris species, family Iridaceae, subgenus Xiphium, oxalis, in the family Oxalidaceae, is the only dicotyledon genus that produces true bulbs. Bulbous plant species cycle through vegetative and reproductive stages, the bulb grows to flowering size during the vegetative stage. Certain environmental conditions are needed to trigger the transition from one stage to the next, bulbs dug up before the foliage period is completed will not bloom the following year but should flower normally in subsequent years. After the foliage period is completed, bulbs may be dug up for replanting elsewhere, any surface moisture should be dried, the bulbs may be stored up to about 4 months for a fall planting. Storing them much longer than that may cause the bulbs to dry out inside, a bulbil is a small bulb, and may be called a bulblet, bulbet, or bulbel. Small bulbs can develop or propagate a large bulb, if one or several moderate-sized bulbs form to replace the original bulb, they are called renewal bulbs.
Increase bulbs are small bulbs that develop either on each of the leaves inside a bulb, some lilies, such as the tiger lily Lilium lancifolium, form small bulbs, called bulbils, in their leaf axils. Several members of the family, including Allium sativum, form bulbils in their flower heads, sometimes as the flowers fade. The so-called tree onion forms small onions which are enough for pickling. Some ferns, such as Hen and Chicken Fern produce new plants at the tips of the fronds pinnae, Patricia The Curious History of the Bulb Vase
Temperate grassland regions include the Pampas of Argentina, southern Brazil and Uruguay as well as the steppes of Eurasia. Lands typically referred to as prairie tend to be in North America, the Central Valley of California is a prairie. The Canadian Prairies occupy vast areas of Manitoba, Prairie is the French word for meadow, but the ultimate root is the Latin pratum. The formation of the North American Prairies started with the upwelling of the Rocky Mountains near Alberta, the mountains created a rain shadow that resulted in lower precipitation rates downwind, creating an environment in which most tree species will not tolerate. The parent material of most prairie soil was distributed during the last glacial advance that began about 110,000 years ago, the glaciers expanding southward scraped the landscape, picking up geologic material and leveling the terrain. As the glaciers retreated about 10,000 years ago, it deposited this material in the form of till, wind based loess deposits form an important parent material for prairie soils.
Tallgrass Prairie evolved over tens of thousands of years with the disturbances of grazing, native ungulates such as bison and white-tailed deer, roamed the expansive, plentiful grassland before European colonization of the Americas. For 10, 000-20,000 years native people used fire annually as a tool to assist in hunting, evidence of ignition sources of fire in the tallgrass prairie are overwhelmingly human as opposed to lightning. Humans, and grazing animals, were participants in the process of prairie formation. Fire has the effect on prairies of removing trees, clearing dead plant matter, fire kills the vascular tissue of trees, but not prairie, as up to 75% of the total plant biomass is below the soil surface and will re-grow from its deep roots. Without disturbance, trees will encroach on a grassland, cast shade and widely spaced oak trees evolved to coexist in the oak savanna ecosystem. In spite of long recurrent droughts and occasional torrential rains, the grasslands of the Great Plains were not subject to soil erosion.
The root systems of native prairie grasses firmly held the soil in place to prevent run-off of soil, when the plant died, the fungi, bacteria returned its nutrients to the soil. These deep roots helped native prairie plants reach water in even the driest conditions, the native grasses suffered much less damage from dry conditions than the farm crops currently grown. Prairie in North America is usually split into three groups, wet and dry and they are generally characterized by tallgrass prairie, mixed, or shortgrass prairie, depending on the quality of soil and rainfall. In wet prairies the soil is very moist, including during most of the growing season. The resulting stagnant water is conducive to the formation of bogs, wet prairies have excellent farming soil. The average precipitation amount is 10-30 inches a year, mesic prairie /ˈmiːzɪk/ has good drainage, but good soil during the growing season
A forest is a large area dominated by trees. Hundreds of more precise definitions of forest are used throughout the world, incorporating factors such as density, tree height, land use, legal standing. According to the widely used Food and Agriculture Organization definition, forests covered four billion hectares or approximately 30 percent of the land area in 2006. Forests are the dominant terrestrial ecosystem of Earth, and are distributed across the globe, Forests account for 75% of the gross primary productivity of the Earths biosphere, and contain 80% of the Earths plant biomass. Forests at different latitudes and elevations form distinctly different ecozones, boreal forests near the poles, tropical forests near the equator, higher elevation areas tend to support forests similar to those at higher latitudes, and amount of precipitation affects forest composition. Human society and forests influence each other in both positive and negative ways, Forests provide ecosystem services to humans and serve as tourist attractions.
Forests can affect peoples health, human activities, including harvesting forest resources, can negatively affect forest ecosystems. Although forest is a term of common parlance, there is no universally recognised precise definition, there are three broad categories of forest definitions in use, land use, and land cover. Land use definitions are based upon the purpose that the land serves. For example, a forest may be defined as any land that is used primarily for production of timber, land cover definitions define forests based upon the type and density of vegetation growing on the land. Such definitions typically define a forest as an area growing trees above some threshold and these thresholds are typically the number of trees per area, the area of ground under the tree canopy or the section of land that is occupied by the cross-section of tree trunks. Under such land cover definitions, and area of land only be defined as forest if it is growing trees, areas that fail to meet the land cover definition may be still included under while immature trees are establishing if they are expected to meet the definition at maturity.
Under land use definitions, there is variation on where the cutoff points are between a forest and savanna. Under some definitions, forests require high levels of tree canopy cover, from 60% to 100%, excluding savannas. Other definitions consider savannas to be a type of forest, the term was not endemic to Romance languages, and cognates in Romance languages, such as Italian foresta and Portuguese floresta, etc. are all ultimately borrowings of the French word. The exact origin of Medieval Latin foresta is obscure, uses of the word forest in English to denote any uninhabited area of non-enclosure are now considered archaic. The word was introduced by the Norman rulers of England as a term denoting an uncultivated area legally set aside for hunting by feudal nobility. These hunting forests were not necessarily wooded much, if at all, however, as hunting forests did often include considerable areas of woodland, the word forest eventually came to mean wooded land more generally
Wood is a porous and fibrous structural tissue found in the stems and roots of trees, and other woody plants. It is a material, a natural composite of cellulose fibers which are strong in tension embedded in a matrix of lignin which resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees, in a living tree it performs a support function, enabling woody plants to grow large or to stand up by themselves. It conveys water and nutrients between the leaves, other growing tissues, and the roots, Wood may refer to other plant materials with comparable properties, and to material engineered from wood, or wood chips or fiber. In 2005, the stock of forests worldwide was about 434 billion cubic meters. As an abundant, carbon-neutral renewable resource, woody materials have been of intense interest as a source of renewable energy, in 1991 approximately 3.5 billion cubic meters of wood were harvested. Dominant uses were for furniture and building construction, a 2011 discovery in the Canadian province of New Brunswick discovered the earliest known plants to have grown wood, approximately 395 to 400 million years ago.
Wood can be dated by carbon dating and in species by dendrochronology to make inferences about when a wooden object was created. People have used wood for millennia for many purposes, primarily as a fuel or as a material for making houses, weapons, packaging, artworks. Constructions using wood date back ten thousand years, buildings like the European Neolithic long house were made primarily of wood. Recent use of wood has changed by the addition of steel. The year-to-year variation in tree-ring widths and isotopic abundances gives clues to the climate at that time. This process is known as growth, it is the result of cell division in the vascular cambium, a lateral meristem. These cells go on to form thickened secondary cell walls, composed mainly of cellulose, hemicellulose, if the distinctiveness between seasons is annual, these growth rings are referred to as annual rings. Where there is little seasonal difference growth rings are likely to be indistinct or absent, if the bark of the tree has been removed in a particular area, the rings will likely be deformed as the plant overgrows the scar.
It is usually lighter in color than that near the portion of the ring. The outer portion formed in the season is known as the latewood or summerwood. However, there are differences, depending on the kind of wood
The word cormous is used to describe plants growing from corms, in analogy to the use of the terms tuberous and bulbous to describe plants growing from tubers and bulbs. A corm consists of one or more internodes with at least one growing point, the tunic of a corm is formed from dead petiole sheaths, remnants of leaves produced in previous years. They act as a covering, protecting the corm from insects, digging animals and water loss. The tunics of some species are thin and papery, at least in plants, however, in some families, such as Iridaceae. For example, some of the species of Watsonia accumulate thick, rot-resistant tunics over a period of some years. Other species, such as many in the genus Lapeirousia, have tunics of hard, internally a typical corm mostly consists of parenchyma cells rich in starch, above a circular basal node from which roots grow. Long-lived cormous plants vary in their long-term development, some regularly replace their older corms with a stack of younger corms, increased more or less seasonally.
By splitting such a stack before the older corm generations wither too badly, other species seldom do anything of that kind, their corms simply grow larger in most seasons. Yet others split when multiple buds or stolons on a large corm sprout independently, corms can be dug up and used to propagate or redistribute the plant. Plants with corms generally can be propagated by cutting the corms into sections, suitably treated, each section with at least one bud usually can generate a new corm. Corms are sometimes confused with true bulbs, they are similar in appearance to bulbs externally. Corms are stems that are structured with solid tissues, which distinguishes them from bulbs. As a result, when a corm is cut in half it is solid, corms are structurally plant stems, with nodes and internodes with buds and produce adventitious roots. On the top of the corm, one or a few grow into shoots that produce normal leaves. Corms can form many small cormlets called cormels, from the areas of the new growing corms.
They are used to propagate corm-forming plants, corms of a number of species of plants are replaced every year by the plant with growth of a new corm, this process starts after the shoot has developed fully expanded leaves. The new corm forms at the base just above the old corm. As the new corm is growing, short stolons are produced that end with the growing small cormels
A perennial plant or simply perennial is a plant that lives for more than two years. The term is used to differentiate a plant from shorter-lived annuals and biennials. The term is widely used to distinguish plants with little or no woody growth from trees and shrubs. Tomato vines, for example, live several years in their natural habitat but are grown as annuals in temperate regions because they dont survive the winter. There is a class of evergreen, or non-herbaceous, perennials, an intermediate class of plants is known as subshrubs, which retain a vestigial woody structure in winter, e. g. Penstemon. The local climate may dictate whether plants are treated as shrubs or perennials, for instance, many varieties of Fuchsia are shrubs in warm regions, but in colder temperate climates may be cut to the ground every year as a result of winter frosts. The symbol for a plant, based on Species Plantarum by Linnaeus, is. Perennial plants can be short-lived or they can be long-lived, as are some plants like trees.
They include an assortment of plant groups from ferns and liverworts to the highly diverse flowering plants like orchids. Plants that flower and fruit only once and die are termed monocarpic or semelparous, most perennials are polycarpic, flowering over many seasons in their lifetime. Perennials typically grow structures that allow them to adapt to living one year to the next through a form of vegetative reproduction rather than seeding. These structures include bulbs, woody crowns, rhizomes plus others and they might have specialized stems or crowns that allow them to survive periods of dormancy over cold or dry seasons during the year. Many perennials have developed specialized features that allow them to extreme climatic. Some have adapted to hot and dry conditions or cold temperatures. Those plants tend to invest a lot of resource into their adaptations and often do not flower, Many perennials produce relatively large seeds, which can have an advantage, with larger seedlings produced after germination that can better compete with other plants.
Some annuals produce many seeds per plant in one season, while some perennials are not under the same pressure to produce large numbers of seeds. In warmer and more favorable climates, perennials grow continuously, in seasonal climates, their growth is limited to the growing season. In some species, perennials retain their foliage all year round, other plants are deciduous perennials, for example, in temperate regions a perennial plant may grow and bloom during the warm part of the year, with the foliage dying back in the winter
A pond is a body of standing water, either natural or artificial, that is usually smaller than a lake. They may arise naturally in floodplains as part of a river system, usually they contain shallow water with marsh and aquatic plants and animals. In the countryside farmers and villagers dig a pond in their backyard or increase the depth of a pond by removing layers of mud during summer season. A wide variety of bodies of water are classified as ponds. Some ponds are created specifically for restoration, including water treatment. Others, like gardens, water features and koi ponds are designed for aesthetic ornamentation as landscape or architectural features. Fish ponds are designed for commercial breeding, and solar ponds designed to store thermal energy. Standing bodies of such as puddles and lakes are often categorized separately from flowing water courses, such as brooks, creeks. Nutrient levels and water quality in ponds can be controlled through natural process such as growth, or through artificial filtration.
The technical distinction between a pond and a lake has not been universally standardized, each of these definitions has met with resistance or disapproval, as the defining characteristics are each difficult to measure or verify. Accordingly, some organizations and researchers have settled on technical definitions of pond, even among organizations and researchers who distinguish lakes from ponds by size alone, there is no universally recognised standard for the maximum size of a pond. The international Ramsar wetland convention sets the limit for pond size as 8 hectares. Other European biologists have set the size limit at 5 ha. In practice, a body of water is called a pond or a lake on a basis, as conventions change from place to place. There are numerous examples in other states of bodies of water less than 10 acres being called lakes, as the case with Crystal Lake shows, marketing purposes may be the driving factor behind some names. Ponds can result from a range of natural processes. Rivers often leave behind ponds in natural flood plains after spring flooding, retreating glaciers can leave behind landscapes filled with small depressions, each developing its own pond, an example is the Prairie Pothole Region of North America.
Some ponds are created by animals, beaver ponds are the best known example, but alligators excavate ponds as well
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. Adventitious roots may be produced from the nodes, the internodes distance one node from another. The term shoots is often confused with stems, shoots generally refers to new plant growth including both stems and other structures like leaves or flowers. In most plants stems are located above the surface but some plants have underground stems. Stems have four main functions which are, Support for and the elevation of leaves, 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 that annually generate new living tissue, Stems are often specialized for storage, asexual reproduction, protection or photosynthesis, including the following, Acaulescent – used to describe stems in plants that appear to be stemless.
Actually these stems are just extremely short, the leaves appearing to rise out of the ground. Arborescent – tree like with woody stems normally with a single trunk, branched – aerial stems are described as being branched or unbranched Bud – an embryonic shoot with immature stem tip. Bulb – a short underground stem with fleshy storage leaves attached, e. g. onion, daffodil. 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 mass or clump or in low growing mats. Cladode – a flattened stem that appears more-or-less leaf like and is specialized for photosynthesis, climbing – stems that cling or wrap around other plants or structures. Corm – a short enlarged underground, storage stem, e. g. taro, decumbent – stems that lie flat on the ground and turn upwards at the ends. Fruticose – stems that grow shrublike with woody like habit, herbaceous – non woody, they die at the end of the growing season.
Pedicel – stems that serve as the stalk of a flower in an inflorescence or infrutescence. Peduncle – a stem that supports an inflorescence Prickle – a sharpened extension of the outer layers
In botany, a tree is a perennial plant with an elongated stem, or trunk, supporting branches and leaves in most species. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are usable as lumber or plants above a specified height. Trees are not a group but include a variety of plant species that have independently evolved a woody trunk. In looser senses, the palms, the tree ferns, bananas. Trees tend to be long-lived, some reaching several thousand years old, the tallest known tree, a coast redwood named Hyperion, stands 115.6 m high. Trees have been in existence for 370 million years and it is estimated that there are just over 3 trillion mature trees in the world. A tree typically has many secondary branches supported clear of the ground by the trunk and this trunk typically contains woody tissue for strength, and vascular tissue to carry materials from one part of the tree to another. For most trees it is surrounded by a layer of bark which serves as a protective barrier, below the ground, the roots branch and spread out widely, they serve to anchor the tree and extract moisture and nutrients from the soil.
Above ground, the divide into smaller branches and shoots. The shoots typically bear leaves, which light energy and convert it into sugars by photosynthesis, providing the food for the trees growth. Flowers and fruit may be present, but some trees, such as conifers, instead have pollen cones and seed cones, such as tree ferns, trees play a significant role in reducing erosion and moderating the climate. They remove carbon dioxide from the atmosphere and store large quantities of carbon in their tissues and forests provide a habitat for many species of animals and plants. Tropical rainforests are one of the most biodiverse habitats in the world, trees provide shade and shelter, timber for construction, fuel for cooking and heating, and fruit for food as well as having many other uses. In parts of the world, forests are shrinking as trees are cleared to increase the amount of available for agriculture. Because of their longevity and usefulness, trees have always revered, with sacred groves in various cultures.
Although tree is a term of common parlance, there is no universally recognised precise definition of what a tree is, either botanically or in common language. In its broadest sense, a tree is any plant with the form of an elongated stem, or trunk. Trees are defined by height, with smaller plants from 0.5 to 10 m being called shrubs