Deciduous
In the fields of horticulture and botany, the term deciduous means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves in the autumn. The term deciduous means "the dropping of a part, no longer needed" and the "falling away after its purpose is finished". In plants, it is the result of natural processes. "Deciduous" has a similar meaning when referring to animal parts, such as deciduous antlers in deer, deciduous teeth in some mammals. Wood from deciduous trees is used in a variety of ways in several industries including lumber for furniture and flooring, bowling pins and baseball bats and furniture, cabinets and paneling. In botany and horticulture, deciduous plants, including trees and herbaceous perennials, are those that lose all of their leaves for part of the year; this process is called abscission. In some cases leaf loss coincides with winter -- namely in polar climates. In other parts of the world, including tropical and arid regions, plants lose their leaves during the dry season or other seasons, depending on variations in rainfall.
The converse of deciduous is evergreen, where foliage is shed on a different schedule from deciduous trees, therefore appearing to remain green year round. Plants that are intermediate may be called semi-deciduous. Other plants are semi-evergreen and lose their leaves before the next growing season, retaining some during winter or dry periods; some trees, including a few species of oak, have desiccated leaves that remain on the tree through winter. Many deciduous plants flower during the period when they are leafless, as this increases the effectiveness of pollination; the absence of leaves improves wind transmission of pollen for wind-pollinated plants and increases the visibility of the flowers to insects in insect-pollinated plants. This strategy is not without risks, as the flowers can be damaged by frost or, in dry season regions, result in water stress on the plant. There is much less branch and trunk breakage from glaze ice storms when leafless, plants can reduce water loss due to the reduction in availability of liquid water during cold winter days.
Leaf drop or abscission involves complex physiological changes within plants. The process of photosynthesis degrades the supply of chlorophylls in foliage; when autumn arrives and the days are shorter or when plants are drought-stressed, deciduous trees decrease chlorophyll pigment production, allowing other pigments present in the leaf to become apparent, resulting in non-green colored foliage. The brightest leaf colors are produced when days grow short and nights are cool, but remain above freezing; these other pigments include carotenoids that are yellow and orange. Anthocyanin pigments produce red and purple colors, though they are not always present in the leaves. Rather, they are produced in the foliage in late summer, when sugars are trapped in the leaves after the process of abscission begins. Parts of the world that have showy displays of bright autumn colors are limited to locations where days become short and nights are cool. In other parts of the world, the leaves of deciduous trees fall off without turning the bright colors produced from the accumulation of anthocyanin pigments.
The beginnings of leaf drop starts when an abscission layer is formed between the leaf petiole and the stem. This layer is formed in the spring during active new growth of the leaf; the cells are sensitive to a plant hormone called auxin, produced by the leaf and other parts of the plant. When auxin coming from the leaf is produced at a rate consistent with that from the body of the plant, the cells of the abscission layer remain connected; the elongation of these cells break the connection between the different cell layers, allowing the leaf to break away from the plant. It forms a layer that seals the break, so the plant does not lose sap. A number of deciduous plants remove nitrogen and carbon from the foliage before they are shed and store them in the form of proteins in the vacuoles of parenchyma cells in the roots and the inner bark. In the spring, these proteins are used as a nitrogen source during the growth of new leaves or flowers. Plants with deciduous foliage have advantages and disadvantages compared to plants with evergreen foliage.
Since deciduous plants lose their leaves to conserve water or to better survive winter weather conditions, they must regrow new foliage during the next suitable growing season. Evergreens suffer greater water loss during the winter and they can experience greater predation pressure when small. Losing leaves in winter may reduce damage from insects. Removing leaves reduces cavitation which can damage xylem vessels in plants; this allows deciduous plants to have xylem vessels with larger diameters and therefore a greater rate of transpiration during the summer growth period
European robin
The European robin, known as the robin or robin redbreast in the British Isles, is a small insectivorous passerine bird a chat, classified as a member of the thrush family but is now considered to be an Old World flycatcher. About 12.5–14.0 cm in length, the male and female are similar in colouration, with an orange breast and face lined with grey, brown upperparts and a whitish belly. It is found across Europe, south to North Africa; the term robin is applied to some birds in other families with red or orange breasts. These include the American robin, a thrush, the Australasian robins of the family Petroicidae, the relationships of which are unclear; the European robin was described by Carl Linnaeus in 1758 in the 10th edition of his Systema Naturae under the binomial name Motacilla rubecula. Its specific epithet rubecula is a diminutive derived from the Latin ruber'red'; the genus Erithacus was introduced by French naturalist Georges Cuvier in 1800, giving the bird its current binomial name E. rubecula.
The genus name Erithacus is from Ancient Greek and refers to an unknown bird, now identified as robin. The genus included the Japanese robin and the Ryukyu robin; these east Asian species were shown in molecular phylogenetic studies to be more similar to a group of other Asian species than to the European robin. In a reorganisation of the genera, the Japanese and the Ryukyu robins were moved to the resurrected genus Larvivora leaving the European robin as the sole member of Erithacus; the phylogenetic analysis placed Erithacus in the subfamily Erithacinae, which otherwise contained only African species, but its exact position with respect to the other genera was not resolved. The distinctive orange breast of both sexes contributed to the European robin's original name of redbreast. In the fifteenth century, when it became popular to give human names to familiar species, the bird came to be known as robin redbreast, shortened to robin; as a given name, Robin is a diminutive of Robert. Other older English names for the bird include robinet.
In American literature of the late 19th century, this robin was called the English robin. Dutch roodborstje, French rouge-gorge, German Rotkehlchen, Italian pettirosso and Spanish petirrojo all refer to the distinctively coloured front; the robin belongs to a group of insectivorous birds that have been variously assigned to the thrushes or "flycatchers", depending on how these groups were perceived taxonomically. The flycatcher-thrush assemblage was re-analysed and the genus Erithacus assigned to a group of thrush-like true flycatchers, the tribe Saxicolini, that includes the common nightingale and the Old World chats. In its large continental Eurasian range, robins vary somewhat, but do not form discrete populations that might be considered subspecies. Robin subspecies are distinguished by forming resident populations on islands and in mountainous areas; the robin found in the British Isles and much of western Europe, Erithacus rubecula melophilus, occurs as a vagrant in adjacent regions. E. r. witherbyi from Northwestern Africa and Sardinia resembles melophilus but for a shorter wing length.
The northeasternmost birds and washed-out in colour are E. r. tataricus. In the southeast of its range, E. r. valens of the Crimean Peninsula, E. r. caucasicus of the Caucasus and N Transcaucasia, E. r. hyrcanus southeastwards into Iran are accepted as distinct. On Madeira and the Azores, the local population has been described as E. r. microrhynchos, although not distinct in morphology, its isolation seems to suggests the subspecies is valid. The most distinct birds are those of Gran Canaria and Tenerife, which may be considered two distinct species or at least two different subspecies, it is distinguished by a white eye-ring, an intensely coloured breast, a grey line that separates the orange-red from the brown colouration. Its belly is white. Cytochrome b sequence data and vocalisations indicate that the Gran Canaria/Tenerife robins are indeed distinct and derived from colonisation by mainland birds some 2 million years ago. Christian Dietzen, Hans-Hinrich Witt and Michael Wink published in 2003 in Avian Science a study called "The phylogeographic differentiation of the European robin Erithacus rubecula on the Canary Islands revealed by mitochondrial DNA sequence data and morphometrics: evidence for a new robin taxon on Gran Canaria?".
In it they concluded that Gran Canaria's robin diverged genetically from their European relatives as far back as 2.3 million years, while the Tenerife ones took another half a million years to make this leap, 1.8 million years ago. The most reason would be a different colonization of the Canaries by this bird, which arrived at the oldest island first and subsequently passed to the neighboring island. A thorough comparison between marionae and superbus is pending to confirm that the first one is a different subspecies. Initial results suggest that birds from Gran Canaria have wings about 10% shorter than those on Tenerife; the west Canary Islands populations are only beginning to diverge genetically. Robins from the western Canary Islands: El Hierro, La Palma and La Gomera are similar to the European type subspecies. Final
Ephemeral plant
An ephemeral plant is one marked by short life cycles. The word ephemeral means transitory or fading. In regard to plants, it refers to several distinct growth strategies; the first, spring ephemeral, refers to perennial plants that emerge in the spring and die back to their underground parts after a short growth and reproduction phase. Desert ephemerals are plants which are adapted to take advantage of the short wet periods in arid climates. Mud-flat annuals take advantage of short periods of low water. In areas subjected to recurring human disturbance, such as plowing, weedy ephemerals are short lived plants whose entire life cycle takes less than a growing season. In each case, the species has a life cycle timed to exploit a short period when resources are available. Spring ephemeral describes a life habit of perennial woodland wildflowers which develop aerial parts of the plant early each spring and quickly bloom, produce seed; the leaves wither leaving only underground structures for the remainder of the year.
This strategy is common in herbaceous communities of deciduous forests as it allows small herbaceous plants to take advantage of the high levels of sunlight reaching the forest floor prior to formation of a canopy by woody plants. Examples include: spring beauties and harbinger of spring. Desert ephemerals, such as the Arabidopsis thaliana, are plants which are adapted to take advantage of the short favourable seasons in deserts. Annual plants in deserts may use the weedy ephemeral strategy to survive in the desert environment; these species survive the dry seasons through seed dormancy. Alternatively, some perennial desert plants may die back to their underground parts and become dormant when there is not enough water available. Most water bodies have natural changes in water level over a year. For example, rivers have higher water periods after melting snow or rainy seasons, followed by natural low water periods. Large lakes have similar seasonal changes, but changes over longer periods of time.
Many short-lived plants annual plants, grow during low water periods set seeds which remain buried in the mud until the next low water period. Many agricultural weeds are ephemeral and reproduce after human disturbance from plowing. Roadside weeds exploit the disturbance from road construction and mowing; these plants have any commercial use, can be invasive weeds. Examples include: Cardamine Cannabis ruderalis. Plants which have short life spans, rapid rates of growth, high levels of seed production are termed ruderals
Monocotyledon
Monocotyledons referred to as monocots, are flowering plants whose seeds contain only one embryonic leaf, or cotyledon. They constitute one of the major groups into which the flowering plants have traditionally been divided, the rest of the flowering plants having two cotyledons and therefore classified as dicotyledons, or dicots. However, molecular phylogenetic research has shown that while the monocots form a monophyletic group or clade, the dicots do not. Monocots have always been recognized as a group, but with various taxonomic ranks and under several different names; the APG III system of 2009 recognises a clade called "monocots" but does not assign it to a taxonomic rank. The monocots include about 60,000 species; the largest family in this group by number of species are the orchids, with more than 20,000 species. About half as many species belong to the true grasses, which are economically the most important family of monocots. In agriculture the majority of the biomass produced; these include not only major grains, but forage grasses, sugar cane, the bamboos.
Other economically important monocot crops include various palms and plantains, gingers and their relatives and cardamom, pineapple, water chestnut, leeks and garlic. Many houseplants are monocot epiphytes. Additionally most of the horticultural bulbs, plants cultivated for their blooms, such as lilies, irises, cannas and tulips, are monocots; the monocots or monocotyledons have, as the name implies, a single cotyledon, or embryonic leaf, in their seeds. This feature was used to contrast the monocots with the dicotyledons or dicots which have two cotyledons. From a diagnostic point of view the number of cotyledons is neither a useful characteristic, nor is it reliable; the single cotyledon is only one of a number of modifications of the body plan of the ancestral monocotyledons, whose adaptive advantages are poorly understood, but may have been related to adaption to aquatic habitats, prior to radiation to terrestrial habitats. Monocots are sufficiently distinctive that there has been disagreement as to membership of this group, despite considerable diversity in terms of external morphology.
However, morphological features that reliably characterise major clades are rare. Thus monocots are distinguishable from other angiosperms both in terms of their uniformity and diversity. On the one hand the organisation of the shoots, leaf structure and floral configuration are more uniform than in the remaining angiosperms, yet within these constraints a wealth of diversity exists, indicating a high degree of evolutionary success. Monocot diversity includes perennial geophytes such as ornamental flowers including and succulent epiphytes, all in the lilioid monocots, major cereal grains in the grass family and forage grasses as well as woody tree-like palm trees, bamboo and bromeliads, bananas and ginger in the commelinid monocots, as well as both emergent and aroids, as well as floating or submerged aquatic plants such as seagrass. Organisation and life formsThe most important distinction is their growth pattern, lacking a lateral meristem that allows for continual growth in diameter with height, therefore this characteristic is a basic limitation in shoot construction.
Although herbaceous, some arboraceous monocots reach great height and mass. The latter include agaves, palms and bamboos; this creates challenges in water transport. Some, such as species of Yucca, develop anomalous secondary growth, while palm trees utilise an anomalous primary growth form described as establishment growth; the axis undergoes primary thickening, that progresses from internode to internode, resulting in a typical inverted conical shape of the basal primary axis. The limited conductivity contributes to limited branching of the stems. Despite these limitations a wide variety of adaptive growth forms has resulted from epiphytic orchids and bromeliads to submarine Alismatales and mycotrophic Burmanniaceae and Triuridaceae. Other forms of adaptation include the climbing vines of Araceae which use negative phototropism to locate host trees, while some palms such as Calamus manan produce the longest shoots in the plant kingdom, up to 185 m long. Other monocots Poales, have adopted a therophyte life form.
LeavesThe cotyledon, the primordial Angiosperm leaf consists of a proximal leaf base or hypophyll and a distal hyperphyll. In monocots the hypophyll tends to be the dominant part in contrast to other angiosperms. From these, considerable diversity arises. Mature monocot leaves are narrow and linear, forming a sheath
Native plant
Native plants are plants indigenous to a given area in geologic time. This includes plants that have developed, occur or existed for many years in an area. An ecosystem consists of interactions of plants and microorganisms with their physical and climatic conditions. Native plants form plant communities and biological interactions with specific flora, fauna and other organisms. For example, some plant species can only reproduce with a continued mutualistic interaction with a certain animal pollinator, the pollinating animal may be dependent on that plant species for a food source; some native plants have adapted to limited, unusual, or harsh conditions, such as cold climates or frequent wildfires. Others can adapt well to different surroundings; the diversity of species across many parts of the world exists only because bioregions are separated by barriers large rivers, oceans and deserts. Humans can introduce species that have never met in their evolutionary history, on varying time scales ranging from days to decades.
Humans are moving species across the globe at an unprecedented rate. Those working to address invasive species view this as an increased risk to indigenous species; as humans introduce plants to new locations for cultivation, or transport them by accident, some of them may become invasive species, damaging native plant communities. Invasive species can have profound effects on ecosystems by changing ecosystem structure, species abundance, community composition. Besides ecological damage, these species can damage agriculture and cultural assets. Government agencies and environmental groups are directing increasing resources to addressing these species; when restoration projects are undertaken to restore a native ecological system disturbed by economic development or other events, they may be inaccurate, incomplete, or pay little or no attention to ecotype accuracy or type conversions. They may fail to restore the original ecological system by overlooking the basics of remediation. Attention paid to the historical distribution of native species is a crucial first step to ensure the ecological integrity of the project.
For example, to prevent erosion of the recontoured sand dunes at the western edge of the Los Angeles International Airport in 1975, landscapers stabilized the backdunes with a “natural” seed mix. The seed mix was representative of coastal sage scrub, an exogenous plant community, instead of the native dune scrub community; as a result, the El Segundo blue butterfly became an endangered species. The El Segundo Blue butterfly population, which had once extended over 3200 acres along the coastal dunes from to Ocean Park to Malaga cove in Palos Verdes, began to recover when the invasive California buckwheat was uprooted so that the butterflies' original native plant host, the dune buckwheat, could regain some of its lost habitat. Native plant organizations such as Wild Ones, native plant societies, Lady Bird Johnson Wildflower Center encourage the use of native plants in public spaces; the identification of local remnant natural areas provides a basis for their work. The use of native cultivars is a disputed practice among native plant advocates.
Returning Essential Wildflowers to America’s Landscapes: Project Milkweed, Xerces Society Milkweeds are the required host plants for caterpillars of the monarch butterfly. Mary M. Walker, "Native Plant Societies of the United States and Canada" Long, John L. 1981. Introduced birds of the world: The worldwide history and influence of birds introduced to new environments. New York, Universe Books, New York City. Noah's Garden: Restoring the Ecology of Our Own Back Yards. Houghton-Mifflin. Vermeij, Geerat J. 1991. When biotas meet: Understanding biotic interchange. Science, 253:1099-1104 "About Native Plants", from the Dorothy King Chapter of the California Native Plant Society
Species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring by sexual reproduction. Other ways of defining species include their karyotype, DNA sequence, behaviour or ecological niche. In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined. While these definitions may seem adequate, when looked at more they represent problematic species concepts. For example, the boundaries between related species become unclear with hybridisation, in a species complex of hundreds of similar microspecies, in a ring species. Among organisms that reproduce only asexually, the concept of a reproductive species breaks down, each clone is a microspecies. All species are given a two-part name, a "binomial"; the first part of a binomial is the genus.
The second part is called the specific epithet. For example, Boa constrictor is one of four species of the genus Boa. None of these is satisfactory definitions, but scientists and conservationists need a species definition which allows them to work, regardless of the theoretical difficulties. If species were fixed and distinct from one another, there would be no problem, but evolutionary processes cause species to change continually, to grade into one another. Species were seen from the time of Aristotle until the 18th century as fixed kinds that could be arranged in a hierarchy, the great chain of being. In the 19th century, biologists grasped. Charles Darwin's 1859 book The Origin of Species explained how species could arise by natural selection; that understanding was extended in the 20th century through genetics and population ecology. Genetic variability arises from mutations and recombination, while organisms themselves are mobile, leading to geographical isolation and genetic drift with varying selection pressures.
Genes can sometimes be exchanged between species by horizontal gene transfer. Viruses are a special case, driven by a balance of mutation and selection, can be treated as quasispecies. Biologists and taxonomists have made many attempts to define species, beginning from morphology and moving towards genetics. Early taxonomists such as Linnaeus had no option but to describe what they saw: this was formalised as the typological or morphological species concept. Ernst Mayr emphasised reproductive isolation, but this, like other species concepts, is hard or impossible to test. Biologists have tried to refine Mayr's definition with the recognition and cohesion concepts, among others. Many of the concepts are quite similar or overlap, so they are not easy to count: the biologist R. L. Mayden recorded about 24 concepts, the philosopher of science John Wilkins counted 26. Wilkins further grouped the species concepts into seven basic kinds of concepts: agamospecies for asexual organisms biospecies for reproductively isolated sexual organisms ecospecies based on ecological niches evolutionary species based on lineage genetic species based on gene pool morphospecies based on form or phenotype and taxonomic species, a species as determined by a taxonomist.
A typological species is a group of organisms in which individuals conform to certain fixed properties, so that pre-literate people recognise the same taxon as do modern taxonomists. The clusters of variations or phenotypes within specimens would differentiate the species; this method was used as a "classical" method of determining species, such as with Linnaeus early in evolutionary theory. However, different phenotypes are not different species. Species named in this manner are called morphospecies. In the 1970s, Robert R. Sokal, Theodore J. Crovello and Peter Sneath proposed a variation on this, a phenetic species, defined as a set of organisms with a similar phenotype to each other, but a different phenotype from other sets of organisms, it differs from the morphological species concept in including a numerical measure of distance or similarity to cluster entities based on multivariate comparisons of a reasonably large number of phenotypic traits. A mate-recognition species is a group of sexually reproducing organisms that recognize one another as potential mates.
Expanding on this to allow for post-mating isolation, a cohesion species is the most inclusive population of individuals having the potential for phenotypic cohesion through intrinsic cohesion mechanisms. A further development of the recognition concept is provided by the biosemiotic concept of species. In microbiology, genes can move even between distantly related bacteria extending to the whole bacterial domain; as a rule of thumb, microbiologists have assumed that kinds of Bacteria or Archaea with 16S ribosomal RNA gene sequences more similar than 97% to each other need to be checked by DNA-DNA hybridisation to decide if they belong to the same species or not. This concept was narrowed in 2006 to a similarity of 98.7%. DNA-DNA hybri
Stigma (botany)
The stigma is the receptive tip of a carpel, or of several fused carpels, in the gynoecium of a flower. The stigma, together with the style and ovary comprises the pistil, which in turn is part of the gynoecium or female reproductive organ of a plant; the stigma forms the distal portion of the stylodia. The stigma is composed of the cells which are receptive to pollen; these may be restricted to the apex of the style or in wind pollinated species, cover a wide surface. The stigma receives pollen and it is on the stigma that the pollen grain germinates. Sticky, the stigma is adapted in various ways to catch and trap pollen with various hairs, flaps, or sculpturings; the pollen may be captured from the air, from visiting insects or other animals, or in rare cases from surrounding water. Stigma can slender to globe shaped to feathery. Pollen is highly desiccated when it leaves an anther. Stigma have been shown to assist in the rehydration of pollen and in promoting germination of the pollen tube. Stigma ensure proper adhesion of the correct species of pollen.
Stigma can play an active role in pollen discrimination and some self-incompatibility reactions, that reject pollen from the same or genetically similar plants, involve interaction between the stigma and the surface of the pollen grain. The stigma is split into lobes, e.g. trifid, may resemble the head of a pin, or come to a point. The shape of the stigma may vary considerably: The style is a narrow upward extension of the ovary, connecting it to the stigmatic papillae, it may be absent in some plants in the case. Styles are tube-like—either long or short; the style can be open with a central canal. Alternatively the style may be closed. Most syncarpous monocots and some eudicots have open styles, while many syncarpous eudicots and grasses have closed styles containing specialised secretory transmitting tissue, linking the stigma to the centre of the ovary; this forms a nutrient rich tract for pollen tube growth. Where there are more than one carpel to the pistil, each may have a separate style-like stylodium, or share a common style.
In Irises and others in the Iridaceae family, the style divides into three petal-like style branches to the base of the style and is called tribrachiate. These are flaps of tissue, running from the perianth tube above the sepal; the stigma is a edge on the underside of the branch, near the end lobes. Style branches appear on Dietes and most species of Moraea. In Crocuses, there are three divided style branches. Hesperantha has a spreading style branch. Alternatively the style may be lobed rather than branched. Gladiolus has a bi-lobed style branch. Freesia, Romulea and Watsonia have bifuracated and recurved style branches. May be terminal, lateral, gynobasic, or subgynobasic. Terminal style position is the commonest pattern. In the subapical pattern the style arises to the side below the apex. A lateral style is found in Rosaceae; the gynobasic style arises from the base of the ovary, or between the ovary lobes and is characteristic of Boraginaceae. Subgynobasic styles characterise Allium. Pollen tubes grow the length of the style to reach the ovules, in some cases self-incompatibility reactions in the style prevent full growth of the pollen tubes.
In some species, including Gasteria at least, the pollen tube is directed to the micropyle of the ovule by the style. Gynoecium Stigma shape and size - English labels Terminal versus gynobasic style Images Gynobasic Diagram
