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
Gland (botany)
In plants, a gland is defined functionally as a plant structure which secretes one or more products. This may be located on or near the plant surface and secrete externally, or be internal to the plant and secrete into a canal or reservoir. Examples include glandular hairs, nectaries and the resin canals in Pinus; the salt glands of mangroves such as Acanthus, Aegiceras and Avicennia are a distinctive multicellular trichome, a glandular hair found on the upper leaf surface and much more densely in the abaxial indumentum. On the upper leaf surface they are sunken in shallow pits, on the lower surface they occur scattered among long nonglandular hairs composed of three or four cells. Development of the glands resembles that of the nonglandular hairs until the three-celled stage, when the short middle stalk cell appears; the salt gland continues to develop to produce two to four vacuolated cells at the level of the epidermis, the stalk cell with an completely cutinized wall, at least eight terminal cells.
The terminal cells have a thin, perforated cuticle which separates from the cell walls apically, leaving an enclosed cavity between them. The secreted salt forms visible crystals. Cannabis plants are broadly covered with sessile glands, other hairs throughout above-ground portions of the plant. There is a high concentration of glands on the bracts of the female plant. After flower formation begins, some of the glands on bracts near the flowers, develop stalks projecting them outward from the plant surface; the glands consist of a layer of disk cells, whose outer surface splits to create a large secretory cavity lined by cell wall and cuticle components. Together the disk cells and secretory cavity form a round head atop the narrow stalk; these cavities come to contain large amounts of cannabidiol in hemp-producing strains, or tetrahydrocannabinol and cannabinol in marijuana-producing strains. These compounds appear to be produced beginning in specialized plastids called lipoplasts; these produce spheres of oily secretions, including terpenes, which pass through the cell membrane and wall to accumulate as vesicles in the secretory cavity.
Final reaction to cannabinoids appears to occur outside the disk cell cyctoplasm. The glands darken as they mature, with loss of cannabinoids over time and undergo abscission from the plant
Carpinus betulus
Carpinus betulus known as the European or common hornbeam, is a hornbeam native to Western Asia and central and southern Europe, including southern England. It requires a warm climate for good growth, occurs only at elevations up to 600 metres, it grows in mixed stands with oak, in some areas beech, is a common tree in scree forests. Hornbeam was known as'Yoke Elm', it is a deciduous small to medium-size tree reaching heights of 15–25 metres 30 m, has a fluted and crooked trunk. The bark is smooth and greenish-grey in old trees; the buds, unlike those of the beech, are 10 mm long at the most, pressed close to the twig. The leaves are alternate, 4–9 cm long, with prominent veins giving a distinctive corrugated texture, a serrated margin, it is monoecious, the wind-pollinated male and female catkins appear in early summer after the leaves. The fruit is a small 7–8 mm long nut surrounded by a three-pointed leafy involucre 3–4 cm long; the wood is heavy and hard, is used for tools and building constructions.
It burns hot and making it suitable for firewood. This was the reason for lopping and hence indirectly the saving of Epping Forest, where the hornbeam was a favoured pollarding tree. Hornbeam was coppiced and pollarded in the past in England, it is still infrequently managed using these traditional methods, but for non-commercial conservation purposes. As a woodland tree traditionally managed in this way, it is frequent in the ancient woodlands of south Essex and north Kent where it occupies more than half of most ancient woods and wood pastures; the leaves provide food for some animals, including Lepidoptera such as the case-bearer moth Coleophora anatipennella. There are a number of notable forests where C. betulus is a dominant tree species, among which are: Epping Forest, Essex/London, UK Halltorp Nature Reserve, Öland, Sweden In England, trees appear to prefer soils with a pH from 3.6 to 4.6 but tolerate up to 7.6. They are found on soils with moderate clay content and avoid soils with high or low clay content.
Carpinus betulus likes moderate soil fertility and moisture. It has a shallow, wide-spreading root system and is marked by the production of stump sprouts when cut back; because it stands up well to cutting back and has dense foliage, it has been much used in landscape gardening as tall hedges and for topiary. The seeds do not germinate till the spring of the second year after sowing; the hornbeam is marked by vigorous natural regeneration. Three fossil fruits of Carpinus betulus have been extracted from borehole samples of the Middle Miocene fresh water deposits in Nowy Sacz Basin, West Carpathians, Poland. Carpinus betulus is cultivated as an ornamental tree, for planting in gardens and parks throughout north west Europe. Both the species and the cultivar C. betulus'Fastigiata' have gained the Royal Horticultural Society's Award of Garden Merit. There are several cultivars, notably: C. betulus'Fastigiata' or'Pyramidalis', a fastigiate tree when young, which has become a popular urban street tree in the United Kingdom and other countries.
C. betulus'Frans Fontaine', a similar fastigiate tree to'Fastigiata' Den virtuella floran: Carpinus betulus distribution Carpinus betulus - information, genetic conservation units and related resources. European Forest Genetic Resources Programme
Bract
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
Leaf
A leaf is an organ of a vascular plant and is the principal lateral appendage of the stem. The leaves and stem together form the shoot. Leaves are collectively referred to as foliage, as in "autumn foliage". A leaf is a thin, dorsiventrally flattened organ borne above ground and specialized for photosynthesis. In most leaves, the primary photosynthetic tissue, the palisade mesophyll, is located on the upper side of the blade or lamina of the leaf but in some species, including the mature foliage of Eucalyptus, palisade mesophyll is present on both sides and the leaves are said to be isobilateral. Most leaves have distinct upper surface and lower surface that differ in colour, the number of stomata, the amount and structure of epicuticular wax and other features. Leaves can have many different shapes and textures; the broad, flat leaves with complex venation of flowering plants are known as megaphylls and the species that bear them, the majority, as broad-leaved or megaphyllous plants. In the clubmosses, with different evolutionary origins, the leaves are simple and are known as microphylls.
Some leaves, such as bulb scales, are not above ground. In many aquatic species the leaves are submerged in water. Succulent plants have thick juicy leaves, but some leaves are without major photosynthetic function and may be dead at maturity, as in some cataphylls and spines. Furthermore, several kinds of leaf-like structures found in vascular plants are not homologous with them. Examples include flattened plant stems called phylloclades and cladodes, flattened leaf stems called phyllodes which differ from leaves both in their structure and origin; some structures of non-vascular plants function much like leaves. Examples include the phyllids of liverworts. Leaves are the most important organs of most vascular plants. Green plants are autotrophic, meaning that they do not obtain food from other living things but instead create their own food by photosynthesis, they capture the energy in sunlight and use it to make simple sugars, such as glucose and sucrose, from carbon dioxide and water. The sugars are stored as starch, further processed by chemical synthesis into more complex organic molecules such as proteins or cellulose, the basic structural material in plant cell walls, or metabolised by cellular respiration to provide chemical energy to run cellular processes.
The leaves draw water from the ground in the transpiration stream through a vascular conducting system known as xylem and obtain carbon dioxide from the atmosphere by diffusion through openings called stomata in the outer covering layer of the leaf, while leaves are orientated to maximise their exposure to sunlight. Once sugar has been synthesized, it needs to be transported to areas of active growth such as the plant shoots and roots. Vascular plants transport sucrose in a special tissue called the phloem; the phloem and xylem are parallel to each other but the transport of materials is in opposite directions. Within the leaf these vascular systems branch to form veins which supply as much of the leaf as possible, ensuring that cells carrying out photosynthesis are close to the transportation system. Leaves are broad and thin, thereby maximising the surface area directly exposed to light and enabling the light to penetrate the tissues and reach the chloroplasts, thus promoting photosynthesis.
They are arranged on the plant so as to expose their surfaces to light as efficiently as possible without shading each other, but there are many exceptions and complications. For instance plants adapted to windy conditions may have pendent leaves, such as in many willows and eucalyptss; the flat, or laminar, shape maximises thermal contact with the surrounding air, promoting cooling. Functionally, in addition to carrying out photosynthesis, the leaf is the principal site of transpiration, providing the energy required to draw the transpiration stream up from the roots, guttation. Many gymnosperms have thin needle-like or scale-like leaves that can be advantageous in cold climates with frequent snow and frost; these are interpreted as reduced from megaphyllous leaves of their Devonian ancestors. Some leaf forms are adapted to modulate the amount of light they absorb to avoid or mitigate excessive heat, ultraviolet damage, or desiccation, or to sacrifice light-absorption efficiency in favour of protection from herbivory.
For xerophytes the major constraint drought. Some window plants such as Fenestraria species and some Haworthia species such as Haworthia tesselata and Haworthia truncata are examples of xerophytes. and Bulbine mesembryanthemoides. Leaves function to store chemical energy and water and may become specialised organs serving other functions, such as tendrils of peas and other legumes, the protective spines of cacti and the insect traps in carnivorous plants such as Nepenthes and Sarracenia. Leaves are the fundamental structural units from which cones are constructed in gymnosperms and from which flowers are constructed in flowering plants; the internal organisation of most kinds of leaves has evolved to maximise exposure of the photosynthetic organelles, the chloroplasts, to light and to increase the absorption of carbon dioxide while at the same time controlling water loss. Their surfaces are waterproofed by the plant cuticle and gas exchange between the mesophyll cells and the atmosphere is controlled by minute openings called stomata which open or close to regulate the rate exchange of carbon dioxide and water vapour into
Botany
Botany called plant science, plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist; the term "botany" comes from the Ancient Greek word βοτάνη meaning "pasture", "grass", or "fodder". Traditionally, botany has included the study of fungi and algae by mycologists and phycologists with the study of these three groups of organisms remaining within the sphere of interest of the International Botanical Congress. Nowadays, botanists study 410,000 species of land plants of which some 391,000 species are vascular plants, 20,000 are bryophytes. Botany originated in prehistory as herbalism with the efforts of early humans to identify – and cultivate – edible and poisonous plants, making it one of the oldest branches of science. Medieval physic gardens attached to monasteries, contained plants of medical importance, they were forerunners of the first botanical gardens attached to universities, founded from the 1540s onwards.
One of the earliest was the Padua botanical garden. These gardens facilitated the academic study of plants. Efforts to catalogue and describe their collections were the beginnings of plant taxonomy, led in 1753 to the binomial system of Carl Linnaeus that remains in use to this day. In the 19th and 20th centuries, new techniques were developed for the study of plants, including methods of optical microscopy and live cell imaging, electron microscopy, analysis of chromosome number, plant chemistry and the structure and function of enzymes and other proteins. In the last two decades of the 20th century, botanists exploited the techniques of molecular genetic analysis, including genomics and proteomics and DNA sequences to classify plants more accurately. Modern botany is a broad, multidisciplinary subject with inputs from most other areas of science and technology. Research topics include the study of plant structure and differentiation, reproduction and primary metabolism, chemical products, diseases, evolutionary relationships and plant taxonomy.
Dominant themes in 21st century plant science are molecular genetics and epigenetics, which are the mechanisms and control of gene expression during differentiation of plant cells and tissues. Botanical research has diverse applications in providing staple foods, materials such as timber, rubber and drugs, in modern horticulture and forestry, plant propagation and genetic modification, in the synthesis of chemicals and raw materials for construction and energy production, in environmental management, the maintenance of biodiversity. Botany originated as the study and use of plants for their medicinal properties. Many records of the Holocene period date early botanical knowledge as far back as 10,000 years ago; this early unrecorded knowledge of plants was discovered in ancient sites of human occupation within Tennessee, which make up much of the Cherokee land today. The early recorded history of botany includes many ancient writings and plant classifications. Examples of early botanical works have been found in ancient texts from India dating back to before 1100 BC, in archaic Avestan writings, in works from China before it was unified in 221 BC.
Modern botany traces its roots back to Ancient Greece to Theophrastus, a student of Aristotle who invented and described many of its principles and is regarded in the scientific community as the "Father of Botany". His major works, Enquiry into Plants and On the Causes of Plants, constitute the most important contributions to botanical science until the Middle Ages seventeen centuries later. Another work from Ancient Greece that made an early impact on botany is De Materia Medica, a five-volume encyclopedia about herbal medicine written in the middle of the first century by Greek physician and pharmacologist Pedanius Dioscorides. De Materia Medica was read for more than 1,500 years. Important contributions from the medieval Muslim world include Ibn Wahshiyya's Nabatean Agriculture, Abū Ḥanīfa Dīnawarī's the Book of Plants, Ibn Bassal's The Classification of Soils. In the early 13th century, Abu al-Abbas al-Nabati, Ibn al-Baitar wrote on botany in a systematic and scientific manner. In the mid-16th century, "botanical gardens" were founded in a number of Italian universities – the Padua botanical garden in 1545 is considered to be the first, still in its original location.
These gardens continued the practical value of earlier "physic gardens" associated with monasteries, in which plants were cultivated for medical use. They supported the growth of botany as an academic subject. Lectures were given about the plants grown in the gardens and their medical uses demonstrated. Botanical gardens came much to northern Europe. Throughout this period, botany remained subordinate to medicine. German physician Leonhart Fuchs was one of "the three German fathers of botany", along with theologian Otto Brunfels and physician Hieronymus Bock. Fuchs and Brunfels broke away from the tradition of copying earlier works to make original observations of their own. Bock created his own system of plant classification. Physician Valerius Cordus authored a botanically and pharmacologically important herbal Historia Plantarum in 1544 and a pharmacopoeia of lasting importance, the Dispensatorium
Mesquite
Mesquite is a common name for several plants in the genus Prosopis, which contains over 40 species of small leguminous trees. They are native to Mexico; the mesquite originates in the Tamaulipan mezquital ecoregion, in the deserts and xeric shrublands biome, located in the southern United States and northeastern Mexico. It has long roots in order to seek water from far underground; the region covers an area of 141,500 km2, encompassing a portion of the Gulf Coastal Plain in southern Texas, northern Tamaulipas, northeastern Coahuila, part of Nuevo León. As a legume, mesquite is one of the few sources of fixed nitrogen in the desert habitat; this tree blooms from spring to summer. It produces fruits known as "pods". Prosopis spp are able to grow up to 8 m tall, with regards to climate, it is deciduous and depending on location and rainfall can have either deep or shallow roots. Prosopis spp is considered long-lived because of the low mortality rate after the dicotyledonous stage and juveniles are able to survive in conditions with low light and drought.
The Cahuilla indigenous people of western North America were known to eat the seeds of mesquite. Prosopis spp has been in North America since the Pliocene era and its wood is dated 3300 yr BP, it is thought to have evolved with megafauna in the New World. The loss of North American megafauna at the end of the Pleistocene era gave way to one theory of how the Prosopis spp was able to survive. One theory is that the loss of the megafauna allowed Prosopis spp to use its fruit pods to attract other organisms to spread its seeds. Another is that Prosopis spp had always been present in grasslands but recurring fires had delayed plant and seed development before the emergence of livestock and grazing; the English word mesquite is borrowed from the Spanish word mezquite, which in turn was borrowed from the Nāhuatl term mizquitl. Mesquite grows as a small shrub in shallow soil or as tall as 50 feet in deep soil with adequate moisture and forms a rounded canopy nearly as wide, they may have multiple trunks with a multitude of branches.
Mesquite has bipinnate leaflets of a light green to blue hue that cast a light to deep shade, depending on the species. Spikes of flowers form in summer that form a flat pod of beans 2 to 6 inches long. Many varieties form thorns; when cut to the ground, the tree can recover. Once the pod is dry, the whole pod can be ground into flour and made into bread. Mesquite is one of the most expensive types of lumber in the US, it was a popular type of wood used by early Spaniards to build ships, but is now used most for high-end rustic furniture and cabinets. Scraps and small pieces are used as wood for cooking with smoke in southern states, bring a premium on the market. Honey mesquite has been introduced to parts of Africa and Australia and is considered by the World Conservation Union as one of the world's most problematic invasive species; the spread into grasslands is attributed to the introduction of domestic livestock, although other factors include climate change and the reduction of fire frequency.
Although Prosopis spp is occurring in these areas these changes have resulted in Prosopis spp being able to outcompete other native plants and is now considered an invasive species due to the fact that it was able to take advantage of vulnerable ecosystems. Prosopis spp is different from most invasive species because it is invasive in its native range as well as introduced ranges, its impacts on the invaded ecosystems include changes to hydrological and nutrient cycling, as well as consequences to biodiversity and primary production. Prosopis spp density and canopy cover influence the herbaceous layer and native shrubs and are factors in the changes to the ecosystem. In the United States, Prosopis spp has become the dominant woody plant on 38,000,000 hectares of semiarid grasslands. North America is its native range and due to an imbalance within this ecosystem has been able to spread rapidly, it is considered the most common and spread "pest" plant in Texas. It is estimated that about 25% of Texas’ grasslands are infested and 16 million acres are so invaded that it is suppressing the majority of grass production.
In Mexico and the US the two most problematic species are velvet mesquite. Australia is affected by the introduction of Prosopis spp, in particular, the P. pallida, P. glandulosa, P. velutina, their hybrid P. juliflora. Prosopis spp is ranked nationally as one of the twenty most significant weeds, it now covers 1 million hectares of land. Prosopis spp was introduced to help with erosion because of its deep root system, it has immediate uses to humans through timber and providing a food source through its pods. Since Australia is a hot and semi-arid region, Prosopis spp has been able to become naturalized. In India Prosopis spp had been introduced decades ago but it was not until that its effects had been studied; this plant species has been pushing out the Indian wild ass. This herbivorous mammal eats the pods of Prosopis spp, one of the intended purposes of its introduction. Through digesting and excreting the seeds the Indian wild asses are providing the habitat needed for germination; the 5,000 square-kilometer Indian Wild Ass Sanctuary is experiencing mesquite invasion of 1.95 square-kilometers a year.
By overtaking the land, the de
