Encephalartos sclavoi, common name Sclavo's cycad, is a critically endangered cycad in the family Zamiaceae. It is endemic to Tanzania, with a population of only ~50 mature plants. Encephalartos sclavoi grows to about 1 metre high; the leaves are dark green and semiglossy. Its seed cones are yellow, it was described in 1990 by Aldo Moretti, D. W. Stevenson and Paolo Deluca, honoring Jean Pierre Sclavo, a French collector of cycads, who first discovered this species
The Silurian is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago, to the beginning of the Devonian Period, 419.2 Mya. The Silurian is the shortest period of the Paleozoic Era; as with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by several million years. The base of the Silurian is set at a series of major Ordovician–Silurian extinction events when 60% of marine species were wiped out. A significant evolutionary milestone during the Silurian was the diversification of jawed fish and bony fish. Multi-cellular life began to appear on land in the form of small, bryophyte-like and vascular plants that grew beside lakes and coastlines, terrestrial arthropods are first found on land during the Silurian. However, terrestrial life would not diversify and affect the landscape until the Devonian; the Silurian system was first identified by British geologist Roderick Murchison, examining fossil-bearing sedimentary rock strata in south Wales in the early 1830s.
He named the sequences for a Celtic tribe of Wales, the Silures, inspired by his friend Adam Sedgwick, who had named the period of his study the Cambrian, from the Latin name for Wales. This naming does not indicate any correlation between the occurrence of the Silurian rocks and the land inhabited by the Silures. In 1835 the two men presented a joint paper, under the title On the Silurian and Cambrian Systems, Exhibiting the Order in which the Older Sedimentary Strata Succeed each other in England and Wales, the germ of the modern geological time scale; as it was first identified, the "Silurian" series when traced farther afield came to overlap Sedgwick's "Cambrian" sequence, provoking furious disagreements that ended the friendship. Charles Lapworth resolved the conflict by defining a new Ordovician system including the contested beds. An early alternative name for the Silurian was "Gotlandian" after the strata of the Baltic island of Gotland; the French geologist Joachim Barrande, building on Murchison's work, used the term Silurian in a more comprehensive sense than was justified by subsequent knowledge.
He divided the Silurian rocks of Bohemia into eight stages. His interpretation was questioned in 1854 by Edward Forbes, the stages of Barrande, F, G and H, have since been shown to be Devonian. Despite these modifications in the original groupings of the strata, it is recognized that Barrande established Bohemia as a classic ground for the study of the earliest fossils; the Llandovery Epoch lasted from 443.8 ± 1.5 to 433.4 ± 2.8 mya, is subdivided into three stages: the Rhuddanian, lasting until 440.8 million years ago, the Aeronian, lasting to 438.5 million years ago, the Telychian. The epoch is named for the town of Llandovery in Wales; the Wenlock, which lasted from 433.4 ± 1.5 to 427.4 ± 2.8 mya, is subdivided into the Sheinwoodian and Homerian ages. It is named after Wenlock Edge in England. During the Wenlock, the oldest-known tracheophytes of the genus Cooksonia, appear; the complexity of later Gondwana plants like Baragwanathia, which resembled a modern clubmoss, indicates a much longer history for vascular plants, extending into the early Silurian or Ordovician.
The first terrestrial animals appear in the Wenlock, represented by air-breathing millipedes from Scotland. The Ludlow, lasting from 427.4 ± 1.5 to 423 ± 2.8 mya, comprises the Gorstian stage, lasting until 425.6 million years ago, the Ludfordian stage. It is named for the town of Ludlow in England; the Přídolí, lasting from 423 ± 1.5 to 419.2 ± 2.8 mya, is the final and shortest epoch of the Silurian. It is named after one locality at the Homolka a Přídolí nature reserve near the Prague suburb Slivenec in the Czech Republic. Přídolí is the old name of a cadastral field area. In North America a different suite of regional stages is sometimes used: Cayugan Lockportian Tonawandan Ontarian Alexandrian In Estonia the following suite of regional stages is used: Ohessaare stage Kaugatuma stage Kuressaare stage Paadla stage Rootsiküla stage Jaagarahu stage Jaani stage Adavere stage Raikküla stage Juuru stage With the supercontinent Gondwana covering the equator and much of the southern hemisphere, a large ocean occupied most of the northern half of the globe.
The high sea levels of the Silurian and the flat land resulted in a number of island chains, thus a rich diversity of environmental settings. During the Silurian, Gondwana continued a slow southward drift to high southern latitudes, but there is evidence that the Silurian icecaps were less extensive than those of the late-Ordovician glaciation; the southern continents remained united during this period. The melting of icecaps and glaciers contributed to a rise in sea level, recognizable from the fact that Silurian sediments overlie eroded Ordovician sediments, forming an unconformity; the continents of Avalonia and Laurentia drifted together near the equator, starting the formation of a second supercontinent known as Euramerica. When the proto-Europe coll
Ginkgo biloba known as ginkgo or gingko known as the maidenhair tree, is the only living species in the division Ginkgophyta, all others being extinct. It is found in fossils dating back 270 million years. Native to China, the tree is cultivated, was cultivated early in human history, it has various uses as a source of food. The genus name Ginkgo is regarded as a misspelling of the Japanese gin kyo, "silver apricot", derived from the Chinese 銀杏 used in Chinese herbalism literature such as Shaoxing Bencao and Compendium of Materia Medica. Engelbert Kaempfer first introduced the spelling ginkgo in his book Amoenitatum Exoticarum, it is considered that he may have misspelled "Ginkjo" as "Ginkgo". This misspelling was included by Carl Linnaeus in his book Mantissa plantarum II and has become the name of the tree's genus. Since the spelling may be confusing to pronounce, ginkgo is sometimes purposefully misspelled as "gingko". Ginkgos are large trees reaching a height of 20–35 m, with some specimens in China being over 50 m.
The tree has an angular crown and long, somewhat erratic branches, is deep rooted and resistant to wind and snow damage. Young trees are tall and slender, sparsely branched. During autumn, the leaves turn a bright yellow fall, sometimes within a short space of time. A combination of resistance to disease, insect-resistant wood and the ability to form aerial roots and sprouts makes ginkgos long-lived, with some specimens claimed to be more than 2,500 years old. Ginkgo is a shade-intolerant species that grows best in environments that are well-watered and well-drained; the species shows a preference for disturbed sites. Accordingly, ginkgo retains a prodigious capacity for vegetative growth, it is capable of sprouting from embedded buds near the base of the trunk in response to disturbances, such as soil erosion. Old individuals are capable of producing aerial roots on the undersides of large branches in response to disturbances such as crown damage; these strategies are evidently important in the persistence of ginkgo.
Extracts of ginkgo leaves contain phenolic acids, proanthocyanidins, flavonoid glycosides, such as myricetin, kaempferol and quercetin, the terpene trilactones and bilobalides. The leaves contain unique ginkgo biflavones, as well as alkylphenols and polyprenols. Ginkgo branches grow in length by growth of shoots with spaced leaves, as seen on most trees. From the axils of these leaves, "spur shoots" develop on second-year growth. Short shoots have short internodes and their leaves are unlobed, they are short and knobby, are arranged on the branches except on first-year growth. Because of the short internodes, leaves appear to be clustered at the tips of short shoots, reproductive structures are formed only on them. In ginkgos, as in other plants that possess them, short shoots allow the formation of new leaves in the older parts of the crown. After a number of years, a short shoot may change into a long shoot, or vice versa; the leaves are unique among seed plants, being fan-shaped with veins radiating out into the leaf blade, sometimes bifurcating, but never anastomosing to form a network.
Two veins enter the leaf blade at the base and fork in two. The leaves are 5–10 cm, but sometimes up to 15 cm long; the old popular name "maidenhair tree" is because the leaves resemble some of the pinnae of the maidenhair fern, Adiantum capillus-veneris. Ginkgos are prized for their autumn foliage, a deep saffron yellow. Leaves of long shoots are notched or lobed, but only from the outer surface, between the veins, they are borne both on the more growing branch tips, where they are alternate and spaced out, on the short, stubby spur shoots, where they are clustered at the tips. Leaves have stomata on both sides. Ginkgos are dioecious, with separate sexes, some trees being female and others being male. Male plants produce small pollen cones with sporophylls, each bearing two microsporangia spirally arranged around a central axis. Female plants do not produce cones. Two ovules are formed at the end of a stalk, after pollination, one or both develop into seeds; the seed is 1.5–2 cm long. Its fleshy outer layer is light yellow-brown and fruit-like.
It is attractive in appearance, but contains butyric acid and smells like rancid butter or vomit when fallen. Beneath the sarcotesta is the hard sclerotesta and a papery endotesta, with the nucellus surrounding the female gametophyte at the center; the fertilization of ginkgo seeds occurs via motile sperm, as in cycads, ferns and algae. The sperm are large and are similar to the sperm of cycads, which are larger. Ginkgo sperm were first discovered by the Japanese botanist Sakugoro Hirase in 1896; the sperm have a complex multi-layered structure, a continuous belt of basal bo
Ephedra is a genus of gymnosperm shrubs, the only genus in its family and order, Ephedrales. The various species of Ephedra are widespread in many lands, native to southwestern North America, southern Europe, northern Africa and central Asia, northern China and western South America. In temperate climates, most Ephedra species grow on shores or in sandy soils with direct sun exposure. Common names in English include joint-pine, Mormon-tea or Brigham tea; the Chinese name for Ephedra species is mahuang. Ephedra is sometimes called sea grape, a common name for the flowering plant Coccoloba uvifera. Plants of the genus Ephedra, including E. sinica and others, have traditionally been used by indigenous people for a variety of medicinal purposes, including treatment of asthma, hay fever and the common cold. The alkaloids ephedrine and pseudoephedrine are active constituents of E. sinica and other members of the genus. These compounds are sympathomimetics with stimulant and decongestant qualities and are chemically substituted amphetamines.
Pollen of Ephedra spp. was found in the Shanidar IV burial site in Iraq, which led to the suggestion that its use as a medicinal plant dates to over 60,000 years ago. Paul B. Pettitt has stated that " recent examination of the microfauna from the strata into which the grave was cut suggests that the pollen was deposited by the burrowing rodent Meriones persicus, common in the Shanidar microfauna and whose burrowing activity can be observed today", it has been suggested. Alkaloids obtained from the species of Ephedra used in herbal medicines, which are used to synthetically prepare pseudoephedrine and ephedrine, can cause cardiovascular events; these events have been associated with arrhythmias, palpitations and myocardial infarction. Caffeine consumption in combination with ephedrine has been reported to increase the risk of these cardiovascular events. Accepted species: Ephedra alata Decaisne 1824 – North Africa, Arabian Peninsula Ephedra altissima Desfontaines 1799 non Bové 1834 non Delile 1813 non Buch 1828 – North Africa, Canary Islands Ephedra americana Humboldt & Bonpland ex Willdenow 1806 – Bolivia, Peru, Chile Ephedra antisyphilitica Berland ex von Meyer 1845 – Clapweed, Erect Ephedra – Texas, New Mexico, Nuevo León, Chihuahua Ephedra aphylla Forsskål 1775 – eastern Mediterranean from Libya and Cyprus to the Persian Gulf Ephedra × arenicola Cutler 1939 – Arizona, Utah Ephedra aspera Engelmann ex Watson 1882 – Boundary Ephedra, Pitamoreal – Texas, New Mexico, Utah, California, Durango, Sinaloa, Baja California Ephedra aurantiaca Takhtajan & Pachomova 1967 – Caucasus, Turkmenistan Ephedra boelckei F.
A. Roig – Argentina Ephedra botschantzevii Pachom. – Kazakhstan, Tuva region of Siberia Ephedra breana Phil. – Peru, Chile, Argentina Ephedra brevifoliata Ghahr. – Iran Ephedra californica S. Wats. – California Ephedra, California Jointfir – California, western Arizona, Baja California Ephedra chilensis C. Presl – Chile, Argentina Ephedra compacta Rose – widespread in much of Mexico Ephedra coryi E. L. Reed – Cory's Ephedra – Texas, New Mexico Ephedra cutleri Peebles – Navajo Ephedra, Cutler's Ephedra, Cutler Mormon-tea, Cutler's Jointfir – Colorado, Arizona, New Mexico, Wyoming Ephedra dahurica Turcz. – Siberia, Mongolia Ephedra dawuensis Y. Yang – Sichuan Ephedra distachya L. – Joint-pine, Jointfir – southern Europe and central Asia from Portugal to Kazakhstan Ephedra × eleutherolepis V. A. Nikitin – Tajikistan Ephedra equisetina Bunge – Ma huang – Caucasus, Central Asia, Mongolia, Hebei, Inner Mongolia, Qinghai, Xinjiang Ephedra fasciculata A. Nelson – Arizona Ephedra, Arizona Jointfir, Desert Mormon-tea – Arizona, Nevada, Utah Ephedra fedtschenkoae Paulsen – Central Asia, Mongolia, Xinjiang Ephedra foeminea Forssk.
– North Africa, Balkans, Middle East. Ex C. A. Mey. – North Africa, Middle East, India Ephedra fragilis Desf. – Mediterranean, Canary Islands, Madeira Ephedra frustillata Miers – Patagonian Ephedra – Chile, Argentina Ephedra funerea Coville & Morton – Death Valley Ephedra, Death Valley Jointfir – California, Nevada Ephedra gerardiana Wallich ex C. A. Meyer – Gerard's Jointfir, Shan Ling Ma Huang – Himalayas, Yunnan, Central Asia Ephedra glauca Regel – Iran, Central Asia, Mongolia Ephedra holoptera Riedl – Iran Ephedra intermedia Schrenk & C. A. Meyer – China, Central Asia, Iran, Pakistan Ephedra × intermixta H. C. Cutler – New Mexico Ephedra kardangensis P. Sharma & P. L. Uniyal – western Himalayas Ephedra khurikensis P. Sharma & P. L. Uniyal – western Himalayas Ephedra laristanica Assadi – Iran Ephedra lepidosperma C. Y. Cheng – northern China Ephedra likiangensis Florin – Guizhou, Tibet, Yunnan Ephedra lomatolepis Schrenk – Kazakhstan, Tuva region of Siberia Ephedra major Host – Mediterranean, Middle East, Central Asia.
– Oman, Yemen Ephedra minuta Florin – Qinghai, Sichuan Ephedra monosperma C. A. Meyer – Siberia, much of China including Tibet and Xinjiang Ephedra multiflora Phil. Ex Stapf – Chile, Argentina Ephedra nevadensis S. Wats. – Nevada Ephedra, Nevada Jointfir, Nevada Mormon-tea – Baja California, Arizona, Utah, Oregon Ephedra ochreata Miers – Argentina Ephedra oxyphylla R
Cycadales is an order of seed plants that includes all the extant cycads. These plants have a stout and woody trunk with a crown of large and stiff, evergreen leaves, they have pinnate leaves. The individual plants are all female. Cycads vary in size from having trunks only a few centimeters to several meters tall, they grow slowly and live long, with some specimens known to be as much as 1,000 years old. Because of the superficial resemblance, they are sometimes confused with and mistaken for palms or ferns, but are only distantly related to either. Cycadales are found across tropical parts of the world, they are found in South and Central America, the Antilles, southeastern United States, Melanesia, Japan, Southeast Asia, Sri Lanka and southern and tropical Africa, where at least 65 species occur. Some can survive in harsh semidesert climates, others in wet rain forest conditions, some in both; some can grow in sand or on rock, some in oxygen-poor, bog-like soils rich in organic material, some in both.
Some are able to grow in full sun, some in full shade, some in both. Some are salt tolerant. Cycadales belong to the biological division Cycadophyta along with the fossil order Medullosales; the three extant families of cycadales are Cycadaceae and Zamiaceae. Though they are a minor component of the plant kingdom today, during the Jurassic period, they were common, they have changed little since the Jurassic, compared to some major evolutionary changes in other plant divisions. Cycads are gymnosperms, meaning their unfertilized seeds are open to the air to be directly fertilized by pollination, as contrasted with angiosperms, which have enclosed seeds with more complex fertilization arrangements. Cycads have specialized pollinators a specific species of beetle, they have been reported to fix nitrogen in association with a cyanobacterium living in the roots. These blue-green algae produce a neurotoxin called BMAA, found in the seeds of cycads; this neurotoxin may enter a human food chain as the cycad seeds may be eaten directly as a source of flour by humans or by wild or feral animals such as bats, humans may eat these animals.
It is hypothesized. Cycads have a cylindrical trunk which does not branch. Leaves grow directly from the trunk, fall when older, leaving a crown of leaves at the top; the leaves grow with new foliage emerging from the top and center of the crown. The trunk may be buried, so the leaves appear to be emerging from the ground and the plant appears to be a basal rosette; the leaves are large in proportion to the trunk size, sometimes larger than the trunk. The leaves are pinnate, with a central leaf stalk from which parallel "ribs" emerge from each side of the stalk, perpendicular to it; the leaves are either compound, or have edges so cut so as to appear compound. Some species have leaves that are bipinnate, which means the leaflets growing along the rachis each have their own subleaflets growing along a rachilla. About 306 species of living Cycadales have been described, in 10–12 genera and two or 3 families of cycads; the classification below is based upon a hierarchical structure based on cladistic analyses of morphological, karyological and phytochemical data.
The number of species in the clade is low compared to the number in most other plant phyla. However and molecular research indicates that the diversity was greater in the history of the phylum; the disparity in molecular sequences is high between the three main lineages of cycads, implying that genetic diversity in the clade was once high. Some defined cycad species can interbreed and produce fertile offspring. Suborder Cycadineae Family Cycadaceae Subfamily Cycadoideae Cycas. About 115 species in the Old World from Africa east to southern Japan and the western Pacific Ocean islands. One species in southern Africa. Two species in Queensland, Australia. Ex Hook. f. Family Zamiaceae Subfamily Encephalartoideae Tribe Diooeae Dioon. 13 species in Mexico and Central America. About 66 species in southeast Africa. About 41 species in Australia. A. Gardner Lepidozamia. Two species in eastern Australia. 26 species in southern Mexico and Central America. Tribe Zamieae Subtribe Microcycadinae Microcycas. One species in Cuba.
Subtribe Zamiinae Chigua. Two species in Colombia. About 65 species in the New World from Georgia, USA south to Bolivia; each family has at least one vein running up the leaf stalk from bottom to top. The Cycadaceae have only one vein in
A mycorrhiza is a symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in its root system. Mycorrhizae play important roles in soil biology and soil chemistry. In a mycorrhizal association, the fungus colonizes the host plant's root tissues, either intracellularly as in arbuscular mycorrhizal fungi, or extracellularly as in ectomycorrhizal fungi; the association is mutualistic, but in particular species or in particular circumstances, mycorrhizae may be variously parasitic in the host plants. A mycorrhiza is a symbiotic association between a fungus; the plant makes organic molecules such as sugars by photosynthesis and supplies them to the fungus, the fungus supplies to the plant water and mineral nutrients, such as phosphorus, taken from the soil. Mycorrhizas are located in the roots of vascular plants, but mycorrhiza-like associations occur in bryophytes and there is fossil evidence that early land plants that lacked roots formed arbuscular mycorrhizal associations.
Most plant species form mycorrhizal associations, though some families like Brassicaceae and Chenopodiaceae cannot. Different forms for the association are detailed in the next section; the most common is the arbuscular type, present in 70% of plant species, including many crop plants such as wheat and rice. Mycorrhizas are divided into ectomycorrhizas and endomycorrhizas; the two types are differentiated by the fact that the hyphae of ectomycorrhizal fungi do not penetrate individual cells within the root, while the hyphae of endomycorrhizal fungi penetrate the cell wall and invaginate the cell membrane. Endomycorrhiza includes arbuscular and orchid mycorrhiza, while arbutoid mycorrhizas can be classified as ectoendomycorrhizas. Monotropoid mycorrhizas form a special category. Ectomycorrhizas, or EcM, are symbiotic associations between the roots of around 10% of plant families woody plants including the birch, eucalyptus, oak and rose families and fungi belonging to the Basidiomycota and Zygomycota.
Some EcM fungi, such as many Leccinum and Suillus, are symbiotic with only one particular genus of plant, while other fungi, such as the Amanita, are generalists that form mycorrhizas with many different plants. An individual tree may have 15 or more different fungal EcM partners at one time. Thousands of ectomycorrhizal fungal species hosted in over 200 genera. A recent study has conservatively estimated global ectomycorrhizal fungal species richness at 7750 species, although, on the basis of estimates of knowns and unknowns in macromycete diversity, a final estimate of ECM species richness would be between 20,000 and 25,000. Ectomycorrhizas consist of a hyphal sheath, or mantle, covering the root tip and a Hartig net of hyphae surrounding the plant cells within the root cortex. In some cases the hyphae may penetrate the plant cells, in which case the mycorrhiza is called an ectendomycorrhiza. Outside the root, ectomycorrhizal extramatrical mycelium forms an extensive network within the soil and leaf litter.
Nutrients can be shown to move between different plants through the fungal network. Carbon has been shown to move from paper birch trees into Douglas-fir trees thereby promoting succession in ecosystems; the ectomycorrhizal fungus Laccaria bicolor has been found to lure and kill springtails to obtain nitrogen, some of which may be transferred to the mycorrhizal host plant. In a study by Klironomos and Hart, Eastern White Pine inoculated with L. bicolor was able to derive up to 25% of its nitrogen from springtails. When compared to non-mycorrhizal fine roots, ectomycorrhizae may contain high concentrations of trace elements, including toxic metals or chlorine; the first genomic sequence for a representative of symbiotic fungi, the ectomycorrhizal basidiomycete L. bicolor, has been published. An expansion of several multigene families occurred in this fungus, suggesting that adaptation to symbiosis proceeded by gene duplication. Within lineage-specific genes those coding for symbiosis-regulated secreted proteins showed an up-regulated expression in ectomycorrhizal root tips suggesting a role in the partner communication.
L. bicolor is lacking enzymes involved in the degradation of plant cell wall components, preventing the symbiont from degrading host cells during the root colonisation. By contrast, L. bicolor possesses expanded multigene families associated with hydrolysis of bacterial and microfauna polysaccharides and proteins. This genome analysis revealed the dual saprotrophic and biotrophic lifestyle of the mycorrhizal fungus that enables it to grow within both soil and living plant roots; this type of mycorrhiza involves plants of the Ericaceae subfamily Arbutoideae. It is however different from ericoid mycorrhiza and resembles ectomycorrhiza, both functionally and in terms of the fungi involved; the difference to ectomycorrhiza is that some hyphae penetrate into the root cells, making this type of mycorrhiza an ectendomycorrhiza. Endomycorrhizas are variable and have been further classified as arbuscular, arbutoid and orchid mycorrhizas. Arbuscular mycorrhizas, or AM, are mycorrhizas whose hyphae penetrate plant cells, producing structures that are either balloon-like or dichotomously branching invaginations as a means of nutrient exchange.
The fungal hyphae invaginate the cell membrane. The struct