Fern
A fern is a member of a group of vascular plants that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e. having specialized tissues that conduct water and nutrients and in having life cycles in which the sporophyte is the dominant phase. Like other vascular plants, ferns have complex leaves called megaphylls, that are more complex than the microphylls of clubmosses. Most ferns are leptosporangiate ferns, sometimes referred to as true ferns, they produce coiled fiddleheads that expand into fronds. The group includes about 10,560 known extant species. Ferns are defined here in the broad sense, being all of the Polypodiopsida, comprising both the leptosporangiate and eusporangiate ferns, the latter itself comprising ferns other than those denominated true ferns, including horsetails or scouring rushes, whisk ferns, marattioid ferns, ophioglossoid ferns. Ferns first appear in the fossil record about 360 million years ago in the late Devonian period, but many of the current families and species did not appear until 145 million years ago in the early Cretaceous, after flowering plants came to dominate many environments.
The fern Osmunda claytoniana is a paramount example of evolutionary stasis. Ferns are not of major economic importance, but some are used for food, medicine, as biofertilizer, as ornamental plants and for remediating contaminated soil, they have been the subject of research for their ability to remove some chemical pollutants from the atmosphere. Some fern species, such as bracken and water fern are significant weeds world wide; some fern genera, such as Azolla can fix nitrogen and make a significant input to the nitrogen nutrition of rice paddies. They play certain roles in mythology and art. Like the sporophytes of seed plants, those of ferns consist of stems and roots. Stems: Fern stems are referred to as rhizomes though they grow underground only in some of the species. Epiphytic species and many of the terrestrial ones have above-ground creeping stolons, many groups have above-ground erect semi-woody trunks; these can reach up to 20 meters tall in a few species. Leaf: The green, photosynthetic part of the plant is technically a megaphyll and in ferns, it is referred to as a frond.
New leaves expand by the unrolling of a tight spiral called a crozier or fiddlehead fern. This uncurling of the leaf is termed circinate vernation. Leaves are divided into a sporophyll. A trophophyll frond is a vegetative leaf analogous to the typical green leaves of seed plants that does not produce spores, instead only producing sugars by photosynthesis. A sporophyll frond is a fertile leaf that produces spores borne in sporangia that are clustered to form sori. In most ferns, fertile leaves are morphologically similar to the sterile ones, they photosynthesize in the same way. In some groups, the fertile leaves are much narrower than the sterile leaves, may have no green tissue at all; the anatomy of fern leaves can either be simple or divided. In tree ferns, the main stalk that connects the leaf to the stem has multiple leaflets; the leafy structures that grow from the stipe are known as pinnae and are again divided into smaller pinnules. Roots: The underground non-photosynthetic structures that take up water and nutrients from soil.
They are always fibrous and structurally are similar to the roots of seed plants. Like all other vascular plants, the diploid sporophyte is the dominant phase or generation in the life cycle; the gametophytes of ferns, are different from those of seed plants. They are free-living and resemble liverworts, whereas those of seed plants develop within the spore wall and are dependent on the parent sporophyte for their nutrition. A fern gametophyte consists of: Prothallus: A green, photosynthetic structure, one cell thick heart or kidney shaped, 3–10 mm long and 2–8 mm broad; the prothallus produces gametes by means of: Antheridia: Small spherical structures that produce flagellate sperm. Archegonia: A flask-shaped structure that produces a single egg at the bottom, reached by the sperm by swimming down the neck. Rhizoids: root-like structures that consist of single elongated cells, that absorb water and mineral salts over the whole structure. Rhizoids anchor the prothallus to the soil. Ferns first appear in the fossil record in the early Carboniferous period.
By the Triassic, the first evidence of ferns related to several modern families appeared. The great fern radiation occurred in the late Cretaceous, when many modern families of ferns first appeared. Ferns were traditionally classified in the class Filices, in a Division of the Plant Kingdom named Pteridophyta or Filicophyta. Pteridophyta is no longer recognised as a valid taxon; the ferns are referred to as Polypodiophyta or, when treated as a subdivision of Tracheophyta, although this name sometimes only refers to leptosporangiate ferns. Traditionally, all of the spore producing vascular plants were informally denominated the pteridophytes, rendering the term synonymous with ferns and fern allies; this can be confusing because members of the division Pteridophyta were denominated pteridophytes. Traditionally, three discrete groups have be
Petiole (botany)
In botany, the petiole is the stalk that attaches the leaf blade to the stem. Outgrowths appearing on each side of the petiole in some species are called stipules. Leaves lacking a petiole are called epetiolate; the petiole is a stalk. In petiolate leaves, the leaf stalk may be long, as in the leaves of celery and rhubarb, short or absent, in which case the blade attaches directly to the stem and is said to be sessile. Subpetiolate leaves are nearly petiolate, or have an short petiole, may appear sessile; the broomrape family Orobanchaceae is an example of a family. In some other plant groups, such as the speedwell genus Veronica and sessile leaves may occur in different species. In the grasses the leaves are apetiolate, but the leaf blade may be narrowed at the junction with the leaf sheath to form a pseudopetiole, as in Pseudosasa japonica. In plants with compound leaves, the leaflets are attached to a continuation of the petiole called the rachis; each leaflet may be attached to the rachis by a short stalk called the petiolule.
There may be swollen regions at either end of the petiole known as pulvina that are composed of a flexible tissue that allows leaf movement. Pulvina are common in the prayer plant family Marantaceae. A pulvinus on a petiolule is called a pulvinulus. In some plants, the petioles are flattened and widened, to become phyllodes or phyllodia, or cladophylls and the true leaves may be reduced or absent. Thus, the phyllode comes to serve the functions of the leaf. Phyllodes are common in the genus Acacia the Australian species, at one time put in Acacia subgenus Phyllodineae. In Acacia koa, the phyllodes are leathery and thick, allowing the tree to survive stressful environments; the petiole allows submerged hydrophytes to have leaves floating at different depths, the petiole being between the node and the stem. In plants such as rhubarb, celery and cardoons the petioles are cultivated as edible crops; the petiole of rhubarb produces the leaf at its end. Botanically it is culinarily used as a fruit. Petiole comes from Latin petiolus, or peciolus "little foot", "stem", an alternative diminutive of pes "foot".
The regular diminutive pediculus is used for "foot stalk". Hyponastic response Pedicel "Petiole". Collier's New Encyclopedia. 1921
Cycad
Cycads are seed plants with a long fossil history that were more abundant and more diverse than they are today. They 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 their superficial resemblance, they are sometimes mistaken for palms or ferns, but they are not related to either group. 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 various cyanobacteria living in the roots. These photosynthetic bacteria 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, so 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 each have their own subleaflets, growing in the same form on the leaflet as the leaflets grow on the stalk of the leaf.
Due to superficial similarities in foliage and plant structure between cycads and palms they are confused with each other. In reality, they belong to different phyla, are not related at all; the similar structure may be evidence of convergent evolution. Despite this, there are still a number of differences between them. For one, both male and female cycads bear a cone-like reproductive structure called a strobilus, while palms are angiosperms and so flower and bear fruit; the mature foliage looks similar between both groups, but the young emerging leaves of a cycad resemble a fiddlehead fern before they unfold and take their place in the rosette, while the leaves of palms are never coiled up and instead are just small versions of the mature frond. Another difference is in the stem. Both plants leave scars on the stem below the rosette where there used to be leaves, but the scars of a cycad are helically arranged and small, while the scars of palms are a circle that wraps around the whole stem.
The stems of cycads are in general rougher and shorter than those of palms. The three extant families of cycads all belong to the order Cycadales, are Cycadaceae and Zamiaceae; these cycads have changed little since the Jurassic, compared to some major evolutionary changes in other plant divisions. Five additional families belonging to the Medullosales became extinct by the end of the Paleozoic Era. Cycads have been traditionally put as related to the extinct Bennettitales, however recent findings show marked differences In reproductive biology and general anatomy putting doubt on the traditional view; as of yet the evidence points to a pteridospermalean origin of cycads and to a close relation to the Ginkgoales, as shown in the following phylogeny: Classification of the Cycadophyta to the rank of family. Class Cycadopsida Order Medullosales † Family Alethopteridaceae Family Cyclopteridaceae Family Neurodontopteridaceae Family ParispermaceaeOrder Cycadales Suborder Cycadineae Family Cycadaceae Suborder Zamiineae Family Stangeriaceae Family Zamiaceae The probable former range of cycads can be inferred from their global distribution.
For example, the family Stangeriaceae only contains three extant species in Australia. Diverse fossils of this family have been dated to 135 mya, indicating that diversity may have been much greater before the Jurassic and late Triassic mass extinction events. However, the cycad fossil record is poor and little can be deduced about the effects of each mass extinction event on their diversity. Instead, correlations can be made between the number of extant angiosperms, it is that cycad diversity was affected more by the great angiosperm radiation in the mid-Cretaceous than by extinctions. Slow cambial growth was first used to define cycads, because of this characteristic the group could not compete with the growing short-lived angiosperms, which now number over 250,000 species, compared to the 1080 remaining gymnosperms, it is surprising that the cycads are still extant, having been faced with extreme competition and five major extinctions. The ability of cycads to survive in dry environments, where plant diversity is lower, may explain their long persistence and longevity.
The cycad fossil record dates to the e
Rhizome
In botany and dendrology, a rhizome is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are called creeping rootstalks or just rootstalks. Rhizomes grow horizontally; the rhizome retains the ability to allow new shoots to grow upwards. A rhizome is the main stem of the plant. A stolon is similar to a rhizome, but a stolon sprouts from an existing stem, has long internodes, generates new shoots at the end, such as in the strawberry plant. In general, rhizomes have short internodes, send out roots from the bottom of the nodes, generate new upward-growing shoots from the top of the nodes. A stem tuber is a thickened part of a rhizome or stolon, enlarged for use as a storage organ. In general, a tuber is high in starch, e.g. the potato, a modified stolon. The term "tuber" is used imprecisely and is sometimes applied to plants with rhizomes. If a rhizome is separated each piece may be able to give rise to a new plant; the plant uses the rhizome to store starches and other nutrients.
These nutrients become useful for the plant when new shoots must be formed or when the plant dies back for the winter. This is a process known as vegetative reproduction and is used by farmers and gardeners to propagate certain plants; this allows for lateral spread of grasses like bamboo and bunch grasses. Examples of plants that are propagated this way include hops, ginger, lily of the valley and sympodial orchids; some rhizomes which are used directly in cooking include ginger, galangal and lotus. Stored rhizomes are subject to bacterial and fungal infections, making them unsuitable for replanting and diminishing stocks. However, rhizomes can be produced artificially from tissue cultures; the ability to grow rhizomes from tissue cultures leads to better stocks for replanting and greater yields. The plant hormones ethylene and jasmonic acid have been found to help induce and regulate the growth of rhizomes in rhubarb. Ethylene, applied externally was found to affect internal ethylene levels, allowing easy manipulations of ethylene concentrations.
Knowledge of how to use these hormones to induce rhizome growth could help farmers and biologists producing plants grown from rhizomes more cultivate and grow better plants. Some plants have rhizomes that grow above ground or that lie at the soil surface, including some Iris species, ferns, whose spreading stems are rhizomes. Plants with underground rhizomes include gingers, the Venus flytrap, Chinese lantern, western poison-oak and Alstroemeria, the weeds Johnson grass, Bermuda grass, purple nut sedge. Rhizomes form a single layer, but in giant horsetails, can be multi-tiered. Many rhizomes have culinary value, some, such as zhe'ergen, are consumed raw. Aspen Corm Mycorrhiza Media related to Rhizomes at Wikimedia Commons The Rhizome Collective for sustainable living
Glossary of leaf morphology
The following is a defined list of terms which are used to describe leaf morphology in the description and taxonomy of plants. Leaves may compound; the edge of the leaf may be smooth or bearing hair, bristles or spines. For more terms describing other aspects of leaves besides their overall morphology see the leaf article. Leaves of most plants include a flat structure called the blade or lamina, but not all leaves are flat, some are cylindrical. Leaves may be simple, with compound, with several leaflets. In flowering plants, as well as the blade of the leaf, there may be a stipules. Leaf structure is described by several terms that include: Being one of the more visible features, leaf shape is used for plant identification. Similar terms are used for other plant parts, such as petals and bracts. Leaf margins are used in visual plant identification because they are consistent within a species or group of species, are an easy characteristic to observe. Edge and margin are interchangeable in the sense that they both refer to the outside perimeter of a leaf.
Leaves may be folded or rolled in various ways. If the leaves are folded in the bud, but unrolls is its called vernation, ptyxis is the folding of an individual leaf in a bud; the Latin word for'leaf', folium, is neuter. In descriptions of a single leaf, the neuter singular ending of the adjective is used, e.g. folium lanceolatum'lanceolate leaf', folium lineare'linear leaf'. In descriptions of multiple leaves, the neuter plural is used, e.g. folia linearia'linear leaves'. Descriptions refer to the plant using the ablative singular or plural, e.g. foliis ovatis'with ovate leaves'. Glossary of botanical terms Glossary of plant morphology Cladophylls are leaf-like petioles Leaf size Sinus Leaflet and Rachis Petiole and Plant stem Phylloclades are flattened stems that resemble leaves Pinnation Plant morphology Taxonomy The Description of Leaves, University of Rochester Fairchild Tropical Botanic Garden Vplants Botany 115 The seed site
Arecaceae
The Arecaceae are a botanical family of perennial plants. Their growth form can be climbers, shrubs and stemless plants, all known as palms; those having a tree form are colloquially called palm trees. They are flowering a family in the monocot order Arecales. 181 genera with around 2600 species are known, most of them restricted to tropical and subtropical climates. Most palms are distinguished by their large, evergreen leaves, known as fronds, arranged at the top of an unbranched stem. However, palms exhibit an enormous diversity in physical characteristics and inhabit nearly every type of habitat within their range, from rainforests to deserts. Palms are among the most extensively cultivated plant families, they have been important to humans throughout much of history. Many common products and foods are derived from palms. In contemporary times, palms are widely used in landscaping, making them one of the most economically important plants. In many historical cultures, because of their importance as food, palms were symbols for such ideas as victory and fertility.
For inhabitants of cooler climates today, palms symbolize the vacations. Whether as shrubs, trees, or vines, palms have two methods of growth: solitary or clustered; the common representation is that of a solitary shoot ending in a crown of leaves. This monopodial character may be exhibited by prostrate and trunk-forming members; some common palms restricted to solitary growth include Roystonea. Palms may instead grow in sparse though dense clusters; the trunk develops an axillary bud at a leaf node near the base, from which a new shoot emerges. The new shoot, in turn, produces a clustering habit results. Sympodial genera include many of the rattans and Rhapis. Several palm genera have both solitary and clustering members. Palms which are solitary may grow in clusters and vice versa; these aberrations suggest. Palms have large, evergreen leaves that are either palmately or pinnately compound and spirally arranged at the top of the stem; the leaves have a tubular sheath at the base that splits open on one side at maturity.
The inflorescence is a spadix or spike surrounded by one or more bracts or spathes that become woody at maturity. The flowers are small and white, radially symmetric, can be either uni- or bisexual; the sepals and petals number three each, may be distinct or joined at the base. The stamens number six, with filaments that may be separate, attached to each other, or attached to the pistil at the base; the fruit is a single-seeded drupe but some genera may contain two or more seeds in each fruit. Like all monocots, palms do not have the ability to increase the width of a stem via the same kind of vascular cambium found in non-monocot woody plants; this explains the cylindrical shape of the trunk, seen in palms, unlike in ring-forming trees. However, many palms, like some other monocots, do have secondary growth, although because it does not arise from a single vascular cambium producing xylem inwards and phloem outwards, it is called "anomalous secondary growth"; the Arecaceae are notable among monocots for their height and for the size of their seeds and inflorescences.
Ceroxylon quindiuense, Colombia's national tree, is the tallest monocot in the world, reaching up to 60 m tall. The coco de mer has the largest seeds of 40 -- 50 cm in diameter and weighing 15 -- 30 kg each. Raffia palms have the largest leaves of any plant, up to 25 m long and 3 m wide; the Corypha species have the largest inflorescence of any plant, up to 7.5 m tall and containing millions of small flowers. Calamus stems. Most palms are native to subtropical climates. Palms can be found in a variety of different habitats, their diversity is highest in lowland forests. South America, the Caribbean, areas of the south Pacific and southern Asia are regions of concentration. Colombia may have the highest number of palm species in one country. There are some palms that are native to desert areas such as the Arabian peninsula and parts of northwestern Mexico. Only about 130 palm species grow beyond the tropics in humid lowland subtropical climates, in highlands in southern Asia, along the rim lands of the Mediterranean Sea.
The northernmost native palm is Chamaerops humilis, which reaches 44°N latitude along the coast of southern France. In the southern hemisphere, the southernmost palm is the Rhopalostylis sapida, which reaches 44°S on the Chatham Islands where an oceanic climate prevails. Cultivation of palms is possible north of subtropical climates, some higher latitude locals such as Ireland, Scotland and the Pacific Northwest feature a few palms in protected locations. Palms inhabit a variety of ecosystems. More than two-thirds of palm species live in humid moist forests, where some species grow tall enough to form part of the canopy and shorter ones form part of the understory; some species form pure stands in areas with poor drainage or regular flooding, including Raphia hookeri, common in coastal freshwater swamps in West Africa. Other palms live in tropical mountain habitats above 1000 m, such as those in the genus Ceroxylon native to the Andes. Palms may live in grasslands and scrublands associated with a water source, in desert oases such as the date palm.
A few palms are adapted to basic lime soils, while others are ada
Blechnum
Blechnum is a genus of between 150–220 species of ferns with a cosmopolitan distribution, in the family Blechnaceae in the eupolypods II clade of the order Polypodiales. By far the greatest species diversity is in tropical regions of the Southern Hemisphere, with only a few species reaching cool temperate latitudes in the Southern Hemisphere and Northern Hemisphere. Most are herbaceous plants. Blechnum varies from most ferns in having a separation of sterile and fertile fronds in the same plant. Selected species The circumscription of the genus has varied since it was established by Linnaeus in 1753; some authors have put many of its species in a segregate genus Lomaria. DNA taxonomy indicates. Several species are grown as ornamental plants in gardens. Blechnum is a host plant for the butterfly, Anartia fatima, or the banded peacock, common in Central America. Huxley, A. ed.. New RHS Dictionary of Gardening. Macmillan Moore, D. M.. Flora of Tierra del Fuego Flora of North America: Blechnum Trees and shrubs in the Andes of Ecuador: Blechnum Flora of China: Blechnum species list
