Powdery mildew is a fungal disease that affects a wide range of plants. Powdery mildew diseases are caused by many different species of fungi in the order Erysiphales, with Podosphaera xanthii being the most reported cause. Erysiphe cichoracearum was reported to be the primary causal organism throughout most of the world. Powdery mildew is one of the easier plant diseases to identify, as its symptoms are quite distinctive. Infected plants stems; the lower leaves are the most affected, but the mildew can appear on any above-ground part of the plant. As the disease progresses, the spots get larger and denser as large numbers of asexual spores are formed, the mildew may spread up and down the length of the plant. Powdery mildew grows well in environments with moderate temperatures. Greenhouses provide an ideal temperate environment for the spread of the disease; this causes harm to agricultural and horticultural practices where powdery mildew may thrive in a greenhouse setting. In an agricultural or horticultural setting, the pathogen can be controlled using chemical methods, bio organic methods, genetic resistance.
It is important to be aware of powdery mildew and its management as the resulting disease can reduce important crop yields. Powdery mildew fungi can only reproduce on their living cell host and reproduce both sexually and asexually. Sexual reproduction is via a type of ascocarp where the genetic material recombines. Powdery mildew fungi must be adapted to their hosts to be able to infect them. Within each ascocarp are several asci. Under optimal conditions, ascospores are released to initiate new infections. Conditions necessary for spore maturation differ among species. Asexual reproduction is. Powder mildew fungi offspring of wheat and barley species are more successful from asexual reproduction compared to sexual reproduction counterparts. Woolly aphids and other sucking insects are vectors of transmission for powdery mildew, other infectious diseases. Woolly aphids in sub temperate climates precede and are an indicator of various infections, including Powdery mildew. Aphids penetrate plant surfaces where they reside and provide a host of potential inoculants through physical, digestive or fecal secretions.
Aphids are an indicator of other potential plant problems. In an agricultural setting, the pathogen can be controlled using chemical methods, genetic resistance, careful farming methods. Chemical fungicides are an effective way to manage powdery mildew disease on plants. Spray programs of chemical fungicides are advised to begin when powdery mildew symptoms and signs are first noticed. Chemical fungicides should be applied on a regular basis for best results against the disease. Chemical control is possible with fungicides such as propiconazole. Effective chemical control is possible with fungicides hexaconazole and penconazole in reducing the mildew. Another chemical treatment involves treating with a silicon calcium silicate slag. Silicon helps the plant cells defend against fungal attack by degrading haustoria and by producing callose and papilla. With silicon treatment, epidermal cells are less susceptible to powdery mildew of wheat. Organic fungicides are an effective way to manage powdery mildew disease on plants by offering alternative modes of action.
Bio organic fungicides are made up of specialized fungi and metals such as copper and sulfur. The most effective non-chemical methods of control against powdery mildew are milk, heavy metals, oils. Metal-based organic fungicides should be applied on a regular basis up until harvest of the host. Sulfur must be applied before the disease has emerged since it prevents fungi spores from germinating. Copper sulfate can cause harm to the host plant. Addition of lime results in a safer fungicide. Neem oil manages powdery mildew on many plants by interfering with the fungus' metabolism and terminating spore production. Sulfur and Fish Oil + Sesame Oil are effective bio fungicides. Milk has long been popular with home gardeners and small-scale organic growers as a treatment for powdery mildew. Milk is diluted with water and sprayed on susceptible plants at the first sign of infection, or as a preventative measure, with repeated weekly application controlling or eliminating the disease. Studies have shown milk's effectiveness as comparable to some conventional fungicides, better than benomyl and fenarimol at higher concentrations.
Milk has proven effective in treating powdery mildew of summer squash, pumpkins and roses. The exact mechanism of action is unknown, but one known effect is that ferroglobulin, a protein in whey, produces oxygen radicals when exposed to sunlight, contact with these radicals is damaging to the fungus. Dilute sprays containing sodium bicarbonate and vegetable or mineral oils in water are recommended for controlling powdery mildew, but such mixtures have limited and inconsistent efficacy. While sodium bicarbonate has been shown to reduce to growth of mildews in lab tests, sprays containing only baking soda and water are not effective in controlling fungal diseases on infected plants, high concentrations of sodium are harmful to plants. Potassium bicarbonate is an effective fungicide against powdery mildew and apple scab, allowed for use in organic farming. Pm3 allel is an effective genetic resistance strategy that protects host species against powdery mildew fungus. Blumeria
The flowering plants known as angiosperms, Angiospermae or Magnoliophyta, are the most diverse group of land plants, with 64 orders, 416 families 13,164 known genera and c. 369,000 known species. Like gymnosperms, angiosperms are seed-producing plants. However, they are distinguished from gymnosperms by characteristics including flowers, endosperm within the seeds, the production of fruits that contain the seeds. Etymologically, angiosperm means a plant; the term comes from the Greek words sperma. The ancestors of flowering plants diverged from gymnosperms in the Triassic Period, 245 to 202 million years ago, the first flowering plants are known from 160 mya, they diversified extensively during the Early Cretaceous, became widespread by 120 mya, replaced conifers as the dominant trees from 100 to 60 mya. Angiosperms differ from other seed plants in several ways, described in the table below; these distinguishing characteristics taken together have made the angiosperms the most diverse and numerous land plants and the most commercially important group to humans.
Angiosperm stems are made up of seven layers. The amount and complexity of tissue-formation in flowering plants exceeds that of gymnosperms; the vascular bundles of the stem are arranged such that the phloem form concentric rings. In the dicotyledons, the bundles in the young stem are arranged in an open ring, separating a central pith from an outer cortex. In each bundle, separating the xylem and phloem, is a layer of meristem or active formative tissue known as cambium. By the formation of a layer of cambium between the bundles, a complete ring is formed, a regular periodical increase in thickness results from the development of xylem on the inside and phloem on the outside; the soft phloem becomes crushed, but the hard wood persists and forms the bulk of the stem and branches of the woody perennial. Owing to differences in the character of the elements produced at the beginning and end of the season, the wood is marked out in transverse section into concentric rings, one for each season of growth, called annual rings.
Among the monocotyledons, the bundles are more numerous in the young stem and are scattered through the ground tissue. They once formed the stem increases in diameter only in exceptional cases; the characteristic feature of angiosperms is the flower. Flowers show remarkable variation in form and elaboration, provide the most trustworthy external characteristics for establishing relationships among angiosperm species; the function of the flower is to ensure fertilization of the ovule and development of fruit containing seeds. The floral apparatus may arise terminally from the axil of a leaf; as in violets, a flower arises singly in the axil of an ordinary foliage-leaf. More the flower-bearing portion of the plant is distinguished from the foliage-bearing or vegetative portion, forms a more or less elaborate branch-system called an inflorescence. There are two kinds of reproductive cells produced by flowers. Microspores, which will divide to become pollen grains, are the "male" cells and are borne in the stamens.
The "female" cells called megaspores, which will divide to become the egg cell, are contained in the ovule and enclosed in the carpel. The flower may consist only of these parts, as in willow, where each flower comprises only a few stamens or two carpels. Other structures are present and serve to protect the sporophylls and to form an envelope attractive to pollinators; the individual members of these surrounding structures are known as petals. The outer series is green and leaf-like, functions to protect the rest of the flower the bud; the inner series is, in general, white or brightly colored, is more delicate in structure. It functions to attract bird pollinators. Attraction is effected by color and nectar, which may be secreted in some part of the flower; the characteristics that attract pollinators account for the popularity of flowers and flowering plants among humans. While the majority of flowers are perfect or hermaphrodite, flowering plants have developed numerous morphological and physiological mechanisms to reduce or prevent self-fertilization.
Heteromorphic flowers have short carpels and long stamens, or vice versa, so animal pollinators cannot transfer pollen to the pistil. Homomorphic flowers may employ a biochemical mechanism called self-incompatibility to discriminate between self and non-self pollen grains. In other species, the male and female parts are morphologically separated, developing on different flowers; the botanical term "Angiosperm", from the Ancient Greek αγγείον, angeíon and σπέρμα, was coined in the form Angiospermae by Paul Hermann in 1690, as the name of one of his primary divisions of the plant kingdom. This included flowering plants possessing seeds enclosed in capsules, distinguished from his Gymnospermae, or flowering plants with achenial or schizo-carpic fruits, the whole fruit or each of its pieces being here regarded as a seed and naked; the term and its antonym were maintained by Carl Linnaeus with the same sense, but with restricted application, in the names of the orders of his class Didynamia. Its use with any
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
Bark is the outermost layers of stems and roots of woody plants. Plants with bark include trees, woody vines, shrubs. Bark is a nontechnical term, it consists of the inner bark and the outer bark. The inner bark, which in older stems is living tissue, includes the innermost area of the periderm; the outer bark in older stems includes the dead tissue on the surface of the stems, along with parts of the innermost periderm and all the tissues on the outer side of the periderm. The outer bark on trees which lies external to the last formed periderm is called the rhytidome. Products derived from bark include: bark shingle siding and wall coverings and other flavorings, tanbark for tannin, latex, poisons, various hallucinogenic chemicals and cork. Bark has been used to make cloth and ropes and used as a surface for paintings and map making. A number of plants are grown for their attractive or interesting bark colorations and surface textures or their bark is used as landscape mulch. What is called bark includes a number of different tissues.
Cork is an external, secondary tissue, impermeable to water and gases, is called the phellem. The cork is produced by the cork cambium, a layer of meristematically active cells which serve as a lateral meristem for the periderm; the cork cambium, called the phellogen, is only one cell layer thick and it divides periclinally to the outside producing cork. The phelloderm, not always present in all barks, is a layer of cells formed by and interior to the cork cambium. Together, the phellem and phelloderm constitute the periderm. Cork cell walls contain suberin, a waxy substance which protects the stem against water loss, the invasion of insects into the stem, prevents infections by bacteria and fungal spores; the cambium tissues, i.e. the cork cambium and the vascular cambium, are the only parts of a woody stem where cell division occurs. Phloem is a nutrient-conducting tissue composed of sieve tubes or sieve cells mixed with parenchyma and fibers; the cortex is the primary tissue of roots. In stems the cortex is between the epidermis layer and the phloem, in roots the inner layer is not phloem but the pericycle.
From the outside to the inside of a mature woody stem, the layers include: Bark Periderm Cork, includes the rhytidome Cork cambium Phelloderm Cortex Phloem Vascular cambium Wood Sapwood Heartwood Pith In young stems, which lack what is called bark, the tissues are, from the outside to the inside: Epidermis, which may be replaced by periderm Cortex Primary and secondary phloem Vascular cambium Secondary and primary xylem. As the stem ages and grows, changes occur that transform the surface of the stem into the bark; the epidermis is a layer of cells that cover the plant body, including the stems, leaves and fruits, that protects the plant from the outside world. In old stems the epidermal layer and primary phloem become separated from the inner tissues by thicker formations of cork. Due to the thickening cork layer these cells die; this dead layer is the rough corky bark that forms around other stems. A secondary covering called the periderm forms on small woody stems and many non-woody plants, composed of cork, the cork cambium, the phelloderm.
The periderm forms from the phellogen. The periderm replaces the epidermis, acts as a protective covering like the epidermis. Mature phellem cells have suberin in their walls to protect the stem from desiccation and pathogen attack. Older phellem cells are dead; the skin on the potato tuber constitutes the cork of the periderm. In woody plants the epidermis of newly grown stems is replaced by the periderm in the year; as the stems grow a layer of cells form under the epidermis, called the cork cambium, these cells produce cork cells that turn into cork. A limited number of cell layers may form interior to the cork cambium, called the phelloderm; as the stem grows, the cork cambium produces new layers of cork which are impermeable to gases and water and the cells outside the periderm, namely the epidermis and older secondary phloem die. Within the periderm are lenticels, which form during the production of the first periderm layer. Since there are living cells within the cambium layers that need to exchange gases during metabolism, these lenticels, because they have numerous intercellular spaces, allow gaseous exchange with the outside atmosphere.
As the bark develops, new lenticels are formed within the cracks of the cork layers. The rhytidome is the most familiar part of bark, being the outer layer that covers the trunks of trees, it is composed of dead cells and is produced by the formation of multiple layers of suberized periderm and phloem tissue. The rhytidome is well developed in older stems and roots of trees. In shrubs, older bark is exfoliated and thick rhytidome accumulates, it is thickest and most distinctive at the trunk or bole of the tree. Bark tissues make up by weight between 10–20% of woody vascular plants and consists of various biopolymers, lignin, suberin and polysaccharides. Up to 40% of the bark tissue is made of lignin which forms an important part of a plant providing stru
John Tradescant the Elder
John Tradescant the Elder, father of John Tradescant the Younger, was an English naturalist, gardener and traveller born in Suffolk, England. He began his career as head gardener to Robert Cecil, 1st Earl of Salisbury at Hatfield House, who initiated Tradescant in travelling by sending him to the Low Countries for fruit trees in 1610/11, he was kept on by Robert's son William, to produce gardens at the family's London house, Salisbury House. He designed gardens on the site of St Augustine's Abbey for Edward Lord Wotton in 1615-23. Tradescant was gardener to the royal favourite George Villiers, 1st Duke of Buckingham, remodelling his gardens at New Hall, Essex and at Burley-on-the-Hill. John Tradescant travelled to the Nikolo-Korelsky Monastery in Arctic Russia in 1618, to the Levant and to Algiers during an expedition against the Barbary pirates in 1620, returned to the Low Countries on Buckingham's behalf in 1624, went to Paris and the Ile de Rhé with Buckingham. After Buckingham's assassination in 1628, he was engaged in 1630 by King Charles I to be Keeper of his Majesty's Gardens and Silkworms at his queen's minor palace, Oatlands Palace in Surrey.
On all his trips he collected seeds and bulbs everywhere and assembled a collection of curiosities of natural history and ethnography which he housed in a large house, "The Ark", in Lambeth, London. The Ark was the prototypical "Cabinet of Curiosity", a collection of rare and strange objects, that became the first museum open to the public in England, the Musaeum Tradescantianum, he gathered specimens through American colonists, including his personal friend John Smith, who bequeathed Tradescant a quarter of his library. From their botanical garden in Lambeth, on the south bank of the Thames, he and his son, introduced many plants into English gardens that have become part of the modern gardener's repertory. A genus of flowering plants is named to honour him. Tradescant Road, off South Lambeth Road in Vauxhall, marks the former boundary of the Tradescant estate; the Tradescant collection, added to by Tradescant's son, John Tradescant the Younger, was given to the University of Oxford by Elias Ashmole.
It was combined with an older University collection to become the Ashmolean Museum, which opened in 1683. He was buried in the churchyard of St-Mary-at-Lambeth, he is the subject of the novel Earthly Joys by Philippa Gregory. Edward Lhuyd - curator of the Ashmolean Museum Leith-Ross, Prudence; the John Tradescants: Gardeners to the Rose and Lily Queen. ISBN 0-720-60612-8. MacGregor, Arthur, ed.. Tradescant's Rarities: Essays on the Foundation of the Ashmolean Museum. ISBN 0-198-13405-3. Allan, Mea; the Tradescants. Their Plants and Museum 1570-1662. London. Potter, Jennifer. Strange Blooms: The Curious Lives and Adventures of the John Tradescants. ISBN 1-843-54334-6. Tradescant Collection at the Ashmolean Museum Vauxhall Society Botany A Chilham garden designed by him
The Balkans known as the Balkan Peninsula, is a geographic area in southeastern Europe with various definitions and meanings, including geopolitical and historical. The region takes its name from the Balkan Mountains that stretch throughout the whole of Bulgaria from the Serbian-Bulgarian border to the Black Sea coast; the Balkan Peninsula is bordered by the Adriatic Sea on the northwest, the Ionian Sea on the southwest, the Aegean Sea in the south and southeast, the Black Sea on the east and northeast. The northern border of the peninsula is variously defined; the highest point of the Balkans is 2,925 metres, in the Rila mountain range. The concept of the Balkan peninsula was created by the German geographer August Zeune in 1808, who mistakenly considered the Balkan Mountains the dominant mountain system of Southeast Europe spanning from the Adriatic Sea to the Black Sea; the term of Balkan Peninsula was a synonym for European Turkey in the 19th century, the former provinces of the Ottoman Empire in Southeast Europe.
It had a geopolitical rather than a geographical definition, further promoted during the creation of the Kingdom of Yugoslavia in the early 20th century. The definition of the Balkan peninsula's natural borders do not coincide with the technical definition of a peninsula and hence modern geographers reject the idea of a Balkan peninsula, while scholars discuss the Balkans as a region; the term has acquired a stigmatized and pejorative meaning related to the process of Balkanization, hence the rather used alternative term for the region is Southeast Europe. The word Balkan comes from Ottoman Turkish balkan'chain of wooded mountains'; the origin of the Turkic word is obscure. From classical antiquity through the Middle Ages, the Balkan Mountains were called by the local Thracian name Haemus. According to Greek mythology, the Thracian king Haemus was turned into a mountain by Zeus as a punishment and the mountain has remained with his name. A reverse name scheme has been suggested. D. Dechev considers that Haemus is derived from a Thracian word *saimon,'mountain ridge'.
A third possibility is that "Haemus" derives from the Greek word "haema" meaning'blood'. The myth relates to a fight between the monster/titan Typhon. Zeus injured Typhon with a thunder bolt and Typhon's blood fell on the mountains, from which they got their name; the earliest mention of the name appears in an early 14th-century Arab map, in which the Haemus mountains are referred to as Balkan. The first attested time the name "Balkan" was used in the West for the mountain range in Bulgaria was in a letter sent in 1490 to Pope Innocent VIII by Buonaccorsi Callimaco, an Italian humanist and diplomat; the Ottomans first mention it in a document dated from 1565. There has been no other documented usage of the word to refer to the region before that, although other Turkic tribes had settled in or were passing through the Peninsula. There is a claim about an earlier Bulgar Turkic origin of the word popular in Bulgaria, however it is only an unscholarly assertion; the word was used by the Ottomans in Rumelia in its general meaning of mountain, as in Kod̲j̲a-Balkan, Čatal-Balkan, Ungurus-Balkani̊, but it was applied to the Haemus mountain.
The name is still preserved in Central Asia with the Balkan Daglary and the Balkan Province of Turkmenistan. English traveler John Morritt introduced this term into the English literature at the end of the 18th-century, other authors started applying the name to the wider area between the Adriatic and the Black Sea; the concept of the "Balkans" was created by the German geographer August Zeune in 1808, who mistakenly considered it as the dominant central mountain system of Southeast Europe spanning from the Adriatic Sea to the Black Sea. During the 1820s, "Balkan became the preferred although not yet exclusive term alongside Haemus among British travelers... Among Russian travelers not so burdened by classical toponymy, Balkan was the preferred term"; the term was not used in geographical literature until the mid-19th century because then scientists like Carl Ritter warned that only the part South of the Balkan Mountains can be considered as a peninsula and considered it to be renamed as "Greek peninsula".
Other prominent geographers who didn't agree with Zeune were Hermann Wagner, Theobald Fischer, Marion Newbigin, Albrecht Penck, while Austrian diplomat Johann Georg von Hahn in 1869 for the same territory used the term Südostereuropäische Halbinsel. Another reason it was not accepted as the definition of European Turkey had a similar land extent. However, after the Congress of Berlin there was a political need for a new term and the Balkans was revitalized, but in the maps the northern border was in Serbia and Montenegro without Greece, while Yugoslavian maps included Croatia and Bosnia; the term Balkan Peninsula was a synonym for European Turkey, the political borders of former Ottoman Empire provinces. The usage of the term changed in the end of the 19th and beginning of the 20th century when was embraced by Serbian geographers, most prominently by Jovan Cvijić, it was done with political reasoning as affirmation for Serbian nationalism on the whole territory of the South Slavs, included anthropological and ethnological studies of the South Slavs through which were claimed various nationalistic and racistic theories.
Through such policies and Yugoslavian maps the term was elevated to the modern status of
A panicle is a much-branched inflorescence. Some authors distinguish it by requiring that the flowers be pedicellate; the branches of a panicle are racemes. A panicle may have indeterminate growth; this type of inflorescence is characteristic of grasses such as oat and crabgrass, as well as other plants such as pistachio and mamoncillo. Botanists use the term paniculate in two ways: "having a true panicle inflorescence" as well as "having an inflorescence with the form but not the structure of a panicle". A corymb may have a paniculate branching structure, with the lower flowers having longer pedicels than the upper, thus giving a flattish top superficially resembling an umbel. Many species in the subfamily Amygdaloideae, such as hawthorns and rowans, produce their flowers in corymbs. Thyrse, a branched inflorescence where the main axis has indeterminate growth, the branches have determinate growth