In botany, an evergreen is a plant that has leaves throughout the year that are always green. This is true if the plant retains its foliage only in warm climates, contrasts with deciduous plants, which lose their foliage during the winter or dry season. There are many different kinds of both trees and shrubs. Evergreens include: most species of conifers, but not all live oak, "ancient" gymnosperms such as cycads most angiosperms from frost-free climates, such as eucalypts and rainforest trees clubmosses and relativesThe Latin binomial term sempervirens, meaning "always green", refers to the evergreen nature of the plant, for instance Cupressus sempervirens Lonicera sempervirens Sequoia sempervirens Leaf persistence in evergreen plants varies from a few months to several decades. Deciduous trees shed their leaves as an adaptation to a cold or dry/wet season. Evergreen trees do lose leaves, but each tree loses its leaves and not all at once. Most tropical rainforest plants are considered to be evergreens, replacing their leaves throughout the year as the leaves age and fall, whereas species growing in seasonally arid climates may be either evergreen or deciduous.
Most warm temperate climate plants are evergreen. In cool temperate climates, fewer plants are evergreen, with a predominance of conifers, as few evergreen broadleaf plants can tolerate severe cold below about −26 °C. In areas where there is a reason for being deciduous, e.g. a cold season or dry season, being evergreen is an adaptation to low nutrient levels. Deciduous trees lose nutrients. In warmer areas, species such as some pines and cypresses grow on disturbed ground. In Rhododendron, a genus with many broadleaf evergreens, several species grow in mature forests but are found on acidic soil where the nutrients are less available to plants. In taiga or boreal forests, it is too cold for the organic matter in the soil to decay so the nutrients in the soil are less available to plants, thus favouring evergreens. In temperate climates, evergreens can reinforce their own survival; these conditions favour the growth of more evergreens and make it more difficult for deciduous plants to persist.
In addition, the shelter provided by existing evergreen plants can make it easier for younger evergreen plants to survive cold and/or drought. Semi-deciduous Helen Ingersoll. "Evergreens". Encyclopedia Americana
Carl Linnaeus known after his ennoblement as Carl von Linné, was a Swedish botanist and zoologist who formalised binomial nomenclature, the modern system of naming organisms. He is known as the "father of modern taxonomy". Many of his writings were in Latin, his name is rendered in Latin as Carolus Linnæus. Linnaeus was born in the countryside of Småland in southern Sweden, he received most of his higher education at Uppsala University and began giving lectures in botany there in 1730. He lived abroad between 1735 and 1738, where he studied and published the first edition of his Systema Naturae in the Netherlands, he returned to Sweden where he became professor of medicine and botany at Uppsala. In the 1740s, he was sent on several journeys through Sweden to find and classify plants and animals. In the 1750s and 1760s, he continued to collect and classify animals and minerals, while publishing several volumes, he was one of the most acclaimed scientists in Europe at the time of his death. Philosopher Jean-Jacques Rousseau sent him the message: "Tell him I know no greater man on earth."
Johann Wolfgang von Goethe wrote: "With the exception of Shakespeare and Spinoza, I know no one among the no longer living who has influenced me more strongly." Swedish author August Strindberg wrote: "Linnaeus was in reality a poet who happened to become a naturalist." Linnaeus has been called Princeps botanicorum and "The Pliny of the North". He is considered as one of the founders of modern ecology. In botany and zoology, the abbreviation L. is used to indicate Linnaeus as the authority for a species' name. In older publications, the abbreviation "Linn." is found. Linnaeus's remains comprise the type specimen for the species Homo sapiens following the International Code of Zoological Nomenclature, since the sole specimen that he is known to have examined was himself. Linnaeus was born in the village of Råshult in Småland, Sweden, on 23 May 1707, he was the first child of Christina Brodersonia. His siblings were Anna Maria Linnæa, Sofia Juliana Linnæa, Samuel Linnæus, Emerentia Linnæa, his father taught him Latin as a small child.
One of a long line of peasants and priests, Nils was an amateur botanist, a Lutheran minister, the curate of the small village of Stenbrohult in Småland. Christina was the daughter of the rector of Samuel Brodersonius. A year after Linnaeus's birth, his grandfather Samuel Brodersonius died, his father Nils became the rector of Stenbrohult; the family moved into the rectory from the curate's house. In his early years, Linnaeus seemed to have a liking for plants, flowers in particular. Whenever he was upset, he was given a flower, which calmed him. Nils spent much time in his garden and showed flowers to Linnaeus and told him their names. Soon Linnaeus was given his own patch of earth. Carl's father was the first in his ancestry to adopt a permanent surname. Before that, ancestors had used the patronymic naming system of Scandinavian countries: his father was named Ingemarsson after his father Ingemar Bengtsson; when Nils was admitted to the University of Lund, he had to take on a family name. He adopted the Latinate name Linnæus after a giant linden tree, lind in Swedish, that grew on the family homestead.
This name was spelled with the æ ligature. When Carl was born, he was named Carl Linnæus, with his father's family name; the son always spelled it with the æ ligature, both in handwritten documents and in publications. Carl's patronymic would have been Nilsson, as in Carl Nilsson Linnæus. Linnaeus's father began teaching him basic Latin and geography at an early age; when Linnaeus was seven, Nils decided to hire a tutor for him. The parents picked a son of a local yeoman. Linnaeus did not like him, writing in his autobiography that Telander "was better calculated to extinguish a child's talents than develop them". Two years after his tutoring had begun, he was sent to the Lower Grammar School at Växjö in 1717. Linnaeus studied going to the countryside to look for plants, he reached the last year of the Lower School when he was fifteen, taught by the headmaster, Daniel Lannerus, interested in botany. Lannerus gave him the run of his garden, he introduced him to Johan Rothman, the state doctor of Småland and a teacher at Katedralskolan in Växjö.
A botanist, Rothman broadened Linnaeus's interest in botany and helped him develop an interest in medicine. By the age of 17, Linnaeus had become well acquainted with the existing botanical literature, he remarks in his journal that he "read day and night, knowing like the back of my hand, Arvidh Månsson's Rydaholm Book of Herbs, Tillandz's Flora Åboensis, Palmberg's Serta Florea Suecana, Bromelii Chloros Gothica and Rudbeckii Hortus Upsaliensis...."Linnaeus entered the Växjö Katedralskola in 1724, where he studied Greek, Hebrew and mathematics, a curriculum designed for boys preparing for the priesthood. In the last year at the gymnasium, Linnaeus's father visited to ask the professors how his son's studies were progressing. Rothman believed otherwise; the doctor offered to have Linnaeus live with his family in Växjö and to teach him physiology and botany. Nils accepted this offer. Rothman showed Linnaeus that botany was a serious sub
The subtropics are geographic and climate zones located between the tropics at latitude 23.5° and temperate zones north and south of the Equator. Subtropical climates are characterized by warm to hot summers and cool to mild winters with infrequent frost. Most subtropical climates fall into two basic types: humid subtropical, where rainfall is concentrated in the warmest months, dry summer climate or, where seasonal rainfall is concentrated in the cooler months. Subtropical climates can occur at high elevations within the tropics, such as in the southern end of the Mexican Plateau and in Vietnam and Taiwan. Six climate classifications use the term to help define the various temperature and precipitation regimes for the planet Earth. A great portion of the world's deserts are located within the subtropics, due to the development of the subtropical ridge. Within savanna regimes in the subtropics, a wet season is seen annually during the summer, when most of the yearly rainfall falls. Within Mediterranean climate regimes, the wet season occurs during the winter.
Areas bordering warm oceans are prone to locally heavy rainfall from tropical cyclones, which can contribute a significant percentage of the annual rainfall. Plants such as palms, mango, pistachio and avocado are grown within the subtropics; the tropics have been defined as lying between the Tropic of Cancer and Tropic of Capricorn, located at latitudes 23.45° north and south, respectively. According to the American Meteorological Society, the poleward fringe of the subtropics is located at latitudes 35° north and south, respectively. Several methods have been used to define the subtropical climate. In the Trewartha climate classification, a subtropical region should have at least eight months with a mean temperature greater than 10 °C and at least one month with a mean temperature under 18 °C. German climatologists Carl Troll and Karlheinz Paffen defined Warm temperate zones as plain and hilly lands having an average temperature of the coldest month between 2 °C and 13 °C in the Northern Hemisphere and between 6 °C and 13 °C in the Southern Hemisphere, excluding oceanic and continental climates.
According to the Troll-Paffen climate classification, there exists one large subtropical zone named the warm-temperate subtropical zone, subdivided into seven smaller areas. According to the E. Neef climate classification, the subtropical zone is divided into two parts: Rainy winters of the west sides and Eastern subtropical climate. According to the Wilhelm Lauer & Peter Frankenberg climate classification, the subtropical zone is divided into three parts: high-continental and maritime. According to the Siegmund/Frankenberg climate classification, subtropical is one of six climate zones in the world. Heating of the earth near the equator leads to large amounts of upward motion and convection along the monsoon trough or intertropical convergence zone; the upper-level divergence over the near-equatorial trough leads to air rising and moving away from the equator aloft. As the air moves towards the mid-latitudes, it cools and sinks, which leads to subsidence near the 30th parallel of both hemispheres.
This circulation leads to the formation of the subtropical ridge. Many of the world's deserts are caused by these climatological high-pressure areas, located within the subtropics; this regime is known as an arid subtropical climate, located in areas adjacent to powerful cold ocean currents. Examples of this climate are the coastal areas of southern Africa, the south of the Canary Islands and the coasts of Peru and Chile; the humid subtropical climate is located on the western side of the subtropical high. Here, unstable tropical airmasses in summer bring convective overturning and frequent tropical downpours, summer is the season of peak annual rainfall. In the winter the monsoon retreats, the drier trade winds bring more stable airmass and dry weather, frequent sunny skies. Areas that have this type of subtropical climate include Australia, Southeast Asia, parts of South America, the deep south of the United States. In areas bounded by warm ocean like the southeastern United States and East Asia, tropical cyclones can contribute to local rainfall within the subtropics.
Japan receives over half of its rainfall from typhoons. The Mediterranean climate is a subtropical climate with a wet season in winter and a dry season in the summer. Regions with this type of climate include the rim lands of the Mediterranean Sea, southwestern Australia around the Perth area, parts of the west coast of South American around Santiago, the coastal areas of western Mexico, coastal California in the United States; these climates do not see hard frosts or snow, which allows plants such as palms and citrus to flourish. As one moves toward the tropical side the slight winter cool season disappears, while at the poleward threshold of the subtropics the winters become cooler; some crops which have been traditionally farmed in tropical climates, such as mango and avocado, are cultivated in the subtropics. Pest control of the crops is less difficult than within the tropics, due to the cooler winters. Tree ferns are grown within subtropical areas within the subtropics and within topography within the tropics.
Dracaena and yucca can grow within the subtropics. Tre
In botany, a bract is a modified or specialized leaf one associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are different from foliage leaves, they texture. They look different from the parts of the flower, such as the petals or sepals; the state of having bracts is referred to as bracteate or bracteolate, conversely the state of lacking them is referred to as ebracteate and ebracteolate, without bracts. Some bracts are brightly-coloured and serve the function of attracting pollinators, either together with the perianth or instead of it. Examples of this type of bract include Euphorbia pulcherrima and Bougainvillea: both of these have large colourful bracts surrounding much smaller, less colourful flowers. In grasses, each floret is enclosed in a pair of papery bracts, called the lemma and palea, while each spikelet has a further pair of bracts at its base called glumes; these bracts form the chaff removed from cereal grain during winnowing. Bats may detect acoustic signals from dish-shaped bracts such as those of Marcgravia evenia.
A prophyll is a leaf-like structure, such as a bracteole, subtending a single pedicel. The term can mean the lower bract on a peduncle; the showy pair of bracts of Euphorbia species in subgenus Lacanthis are the cyathophylls. Bracts subtend the cone scales in the seed cones of many conifers, in some cases, such as Pseudotsuga, they extend beyond the cone scales. A small bract is called a bractlet. Technically this is any bract. Bracts that appear in a whorl subtending an inflorescence are collectively called an involucre. An involucre is a common feature beneath the inflorescences of many Apiaceae, Asteraceae and Polygonaceae; each flower in an inflorescence may have its own whorl of bracts, in this case called an involucel. In this case they may be called chaff, paleas, or receptacular bracts and are minute scales or bristles. Many asteraceous plants have bracts at the base of each inflorescence; the term involucre is used for a conspicuous bract or bract pair at the base of an inflorescence. In the family Betulaceae, notably in the genera Carpinus and Corylus, the involucre is a leafy structure that protects the developing nuts.
Beggar-tick has narrow involucral bracts surrounding each inflorescence, each of which has a single bract below it. There is a pair of leafy bracts on the main stem and below those a pair of leaves. An epicalyx, which forms an additional whorl around the calyx of a single flower, is a modification of bracteoles In other words, the epicalyx is a group of bracts resembling a calyx or bracteoles forming a whorl outer to the calyx, it is a calyx-like extra whorl of floral appendages. Each individual segment of the epicalyx is called an episepal because they resemble the sepals in them, they are present in the Hibiscus family. Fragaria may not have an epicalyx. A spathe is a large bract or pair of bracts forming a sheath to enclose the flower cluster of such plants as palms, irises and dayflowers. Habranthus tubispathus in the Amaryllidaceae derives its specific name from its tuberous spathe. In many arums, the spathe is petal-like, attracting pollinators to the flowers arranged on a type of spike called a spadix
Plants are multicellular, predominantly photosynthetic eukaryotes of the kingdom Plantae. Plants were treated as one of two kingdoms including all living things that were not animals, all algae and fungi were treated as plants. However, all current definitions of Plantae exclude the fungi and some algae, as well as the prokaryotes. By one definition, plants form the clade Viridiplantae, a group that includes the flowering plants and other gymnosperms and their allies, liverworts and the green algae, but excludes the red and brown algae. Green plants obtain most of their energy from sunlight via photosynthesis by primary chloroplasts that are derived from endosymbiosis with cyanobacteria, their chloroplasts contain b, which gives them their green color. Some plants are parasitic or mycotrophic and have lost the ability to produce normal amounts of chlorophyll or to photosynthesize. Plants are characterized by sexual reproduction and alternation of generations, although asexual reproduction is common.
There are about 320 thousand species of plants, of which the great majority, some 260–290 thousand, are seed plants. Green plants provide a substantial proportion of the world's molecular oxygen and are the basis of most of Earth's ecosystems on land. Plants that produce grain and vegetables form humankind's basic foods, have been domesticated for millennia. Plants have many cultural and other uses, as ornaments, building materials, writing material and, in great variety, they have been the source of medicines and psychoactive drugs; the scientific study of plants is known as a branch of biology. All living things were traditionally placed into one of two groups and animals; this classification may date from Aristotle, who made the distincton between plants, which do not move, animals, which are mobile to catch their food. Much when Linnaeus created the basis of the modern system of scientific classification, these two groups became the kingdoms Vegetabilia and Animalia. Since it has become clear that the plant kingdom as defined included several unrelated groups, the fungi and several groups of algae were removed to new kingdoms.
However, these organisms are still considered plants in popular contexts. The term "plant" implies the possession of the following traits multicellularity, possession of cell walls containing cellulose and the ability to carry out photosynthesis with primary chloroplasts; when the name Plantae or plant is applied to a specific group of organisms or taxon, it refers to one of four concepts. From least to most inclusive, these four groupings are: Another way of looking at the relationships between the different groups that have been called "plants" is through a cladogram, which shows their evolutionary relationships; these are not yet settled, but one accepted relationship between the three groups described above is shown below. Those which have been called "plants" are in bold; the way in which the groups of green algae are combined and named varies between authors. Algae comprise several different groups of organisms which produce food by photosynthesis and thus have traditionally been included in the plant kingdom.
The seaweeds range from large multicellular algae to single-celled organisms and are classified into three groups, the green algae, red algae and brown algae. There is good evidence that the brown algae evolved independently from the others, from non-photosynthetic ancestors that formed endosymbiotic relationships with red algae rather than from cyanobacteria, they are no longer classified as plants as defined here; the Viridiplantae, the green plants – green algae and land plants – form a clade, a group consisting of all the descendants of a common ancestor. With a few exceptions, the green plants have the following features in common, they undergo closed mitosis without centrioles, have mitochondria with flat cristae. The chloroplasts of green plants are surrounded by two membranes, suggesting they originated directly from endosymbiotic cyanobacteria. Two additional groups, the Rhodophyta and Glaucophyta have primary chloroplasts that appear to be derived directly from endosymbiotic cyanobacteria, although they differ from Viridiplantae in the pigments which are used in photosynthesis and so are different in colour.
These groups differ from green plants in that the storage polysaccharide is floridean starch and is stored in the cytoplasm rather than in the plastids. They appear to have had a common origin with Viridiplantae and the three groups form the clade Archaeplastida, whose name implies that their chloroplasts were derived from a single ancient endosymbiotic event; this is the broadest modern definition of the term'plant'. In contrast, most other algae not only have different pigments but have chloroplasts with three or four surrounding membranes, they are not close relatives of the Archaeplastida having acquired chloroplasts separately from ingested or symbiotic green and red algae. They are thus not included in the broadest modern definition of the plant kingdom, although they were in the past; the green plants or Viridiplantae were traditionally divided into the green algae (including
A sepal is a part of the flower of angiosperms. Green, sepals function as protection for the flower in bud, as support for the petals when in bloom; the term sepalum was coined by Noël Martin Joseph de Necker in 1790, derived from the Greek σκεπη, a covering. Collectively the sepals are called the outermost whorl of parts that form a flower; the word calyx was adopted from the Latin calyx, not to be confused with a cup or goblet. Calyx derived from the Greek κάλυξ, a bud, a calyx, a husk or wrapping, while calix derived from the Greek κυλιξ, a cup or goblet, the words have been used interchangeably in botanical Latin. After flowering, most plants have no more use for the calyx which becomes vestigial; some plants retain a thorny calyx, either dried or live, as protection for seeds. Examples include species of Acaena, some of the Solanaceae, the water caltrop, Trapa natans. In some species the calyx not only persists after flowering, but instead of withering, begins to grow until it forms a bladder-like enclosure around the fruit.
This is an effective protection against some kinds of birds and insects, for example in Hibiscus trionum and the Cape gooseberry. Morphologically, both sepals and petals are modified leaves; the calyx and the corolla are the outer sterile whorls of the flower, which together form what is known as the perianth. The term tepal is applied when the parts of the perianth are difficult to distinguish, e.g. the petals and sepals share the same color, or the petals are absent and the sepals are colorful. When the undifferentiated tepals resemble petals, they are referred to as "petaloid", as in petaloid monocots, orders of monocots with brightly coloured tepals. Since they include Liliales, an alternative name is lilioid monocots. Examples of plants in which the term tepal is appropriate include genera such as Tulipa. In contrast, genera such as Rosa and Phaseolus have well-distinguished petals; the number of sepals in a flower is its merosity. Flower merosity is indicative of a plant's classification.
The merosity of a eudicot flower is four or five. The merosity of a monocot or palaeodicot flower is a multiple of three; the development and form of the sepals vary among flowering plants. They may be fused together; the sepals are much reduced, appearing somewhat awn-like, or as scales, teeth, or ridges. Most such structures protrude until the fruit is mature and falls off. Examples of flowers with much reduced perianths are found among the grasses. In some flowers, the sepals are fused towards the base. In other flowers a hypanthium includes the bases of sepals and the attachment points of the stamens. Plant morphology
An inflorescence is a group or cluster of flowers arranged on a stem, composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants; the modifications can involve the length and the nature of the internodes and the phyllotaxis, as well as variations in the proportions, swellings, adnations and reduction of main and secondary axes. Inflorescence can be defined as the reproductive portion of a plant that bears a cluster of flowers in a specific pattern; the stem holding the whole inflorescence is called a peduncle and the major axis holding the flowers or more branches within the inflorescence is called the rachis. The stalk of each single flower is called a pedicel. A flower, not part of an inflorescence is called a solitary flower and its stalk is referred to as a peduncle. Any flower in an inflorescence may be referred to as a floret when the individual flowers are small and borne in a tight cluster, such as in a pseudanthium.
The fruiting stage of an inflorescence is known as an infructescence. Inflorescences may be complex; the rachis may be one of several types, including single, umbel, spike or raceme. Inflorescences are described by many different characteristics including how the flowers are arranged on the peduncle, the blooming order of the flowers and how different clusters of flowers are grouped within it; these terms are general representations. Inflorescences have modified shoots foliage different from the vegetative part of the plant. Considering the broadest meaning of the term, any leaf associated with an inflorescence is called a bract. A bract is located at the node where the main stem of the inflorescence forms, joined to the main stem of the plant, but other bracts can exist within the inflorescence itself, they serve a variety of functions which include protecting young flowers. According to the presence or absence of bracts and their characteristics we can distinguish: Ebracteate inflorescences: No bracts in the inflorescence.
Bracteate inflorescences: The bracts in the inflorescence are specialised, sometimes reduced to small scales, divided or dissected. Leafy inflorescences: Though reduced in size, the bracts are unspecialised and look like the typical leaves of the plant, so that the term flowering stem is applied instead of inflorescence; this use is not technically correct, as, despite their'normal' appearance, these leaves are considered, in fact, bracts, so that'leafy inflorescence' is preferable. Leafy-bracted inflorescences: Intermediate between bracteate and leafy inflorescence. If many bracts are present and they are connected to the stem, like in the family Asteraceae, the bracts might collectively be called an involucre. If the inflorescence has a second unit of bracts further up the stem, they might be called an involucel. Plant organs can grow according to two different schemes, namely monopodial or racemose and sympodial or cymose. In inflorescences these two different growth patterns are called indeterminate and determinate and indicate whether a terminal flower is formed and where flowering starts within the inflorescence.
Indeterminate inflorescence: Monopodial growth. The terminal bud keeps forming lateral flowers. A terminal flower is never formed. Determinate inflorescence: Sympodial growth; the terminal bud forms a terminal flower and dies out. Other flowers grow from lateral buds. Indeterminate and determinate inflorescences are sometimes referred to as open and closed inflorescences respectively; the indeterminate patterning of flowers is derived from determinate flowers. It is suggested that indeterminate flowers have a common mechanism that prevents terminal flower growth. Based on phylogenetic analyses, this mechanism arose independently multiple times in different species. In an indeterminate inflorescence there is no true terminal flower and the stem has a rudimentary end. In many cases the last true flower formed by the terminal bud straightens up, appearing to be a terminal flower. A vestige of the terminal bud may be noticed higher on the stem. In determinate inflorescences the terminal flower is the first to mature, while the others tend to mature starting from the bottom of the stem.
This pattern is called acropetal maturation. When flowers start to mature from the top of the stem, maturation is basipetal, while when the central mature first, divergent; as with leaves, flowers can be arranged on the stem according to many different patterns. See'Phyllotaxis' for in-depth descriptions Similarly arrangement of leaf in bud is called Ptyxis. Metatopy is the placement of organs out of their expected position: metatopy occurs in inflorescences when unequal growth rates alter different areas of the axis and the organs attached to the axis; when a single or a cluster of flower is located at the axil of a bract, the location of the bract in relation to the stem holding the flower is indicated by the use of different terms and may be a useful diagnostic indicator. Typical placement of bracts include: Some plants have bracts that subtend the inflorescence, where the flowers are on branched stalks.