Nandina
Nandina domestica known as nandina, heavenly bamboo or sacred bamboo, is a species of flowering plant in the family Berberidaceae, native to eastern Asia from the Himalayas to Japan. It is the only member of the monotypic genus Nandina. Despite the common name, it is not a bamboo but an erect evergreen shrub up to 2 m tall by 1.5 m wide, with numerous unbranched stems growing from ground level. The glossy leaves are sometimes deciduous in colder areas, 50–100 cm long, bi- to tri-pinnately compound, with the individual leaflets 4–11 cm long and 1.5–3 cm broad. The young leaves in spring are brightly coloured pink to red before turning green; the flowers are white. The fruit is a bright red berry 5–10 mm diameter, ripening in late autumn and persisting through the winter. All parts of the plant are poisonous, containing compounds that decompose to produce hydrogen cyanide, could be fatal if ingested; the plant is placed in Toxicity Category 4, the category "generally considered non-toxic to humans", but the berries are considered toxic to cats and grazing animals.
Excessive consumption of the berries will kill birds such as cedar waxwings, because they are subject to cyanide toxicosis, resulting in death to multiple individuals at one time. The berries contain alkaloids such as nantenine, used in scientific research as an antidote to MDMA. Nandina is considered invasive in North Carolina, Tennessee and Florida, it was placed on the Florida Exotic Pest Plant Council's invasive list as a Category I species, the highest listing. It has been observed in the wild in Florida in Gadsden, Jackson and Citrus counties, in conservation areas and floodplains. In general, the purchase or continued cultivation of non-sterile varieties in the southeastern United States is discouraged. Nandina is becoming invasive in wild areas farther north, in May 2017 was added to the Maryland invasive plant list with a tier 2 status. Although grown extensively in Texas because of its tolerance for dry conditions, fruiting varieties of Nandina are considered invasive there; this is due to birds spreading seeds into natural areas where Nandina proliferates and crowds out native species, both through seeding and by the growth of rhizomatous underground stems.
N. domestica, grown in Chinese and Japanese gardens for centuries, was brought to Western gardens by William Kerr, who sent it to London in his first consignment from Canton, in 1804. The English, unsure of its hardiness, kept it in greenhouses at first; the scientific name given to it by Carl Peter Thunberg is a Latinized version of a Japanese name for the plant, nan-ten. Nandina is grown in gardens as an ornamental plant. Over 65 cultivars have been named in Japan, where the species is popular and a national Nandina society exists. In Shanghai berried sprays of nandina are sold in the streets at New Year, for the decoration of house altars and temples. Nandina does not berry profusely in Great Britain, but it can be grown in USDA hardiness zones 6–10 with some cultivars hardy into zone 5. Nandina can take heat and cold, from −10 to 110 °F, it needs no pruning, but can spread via underground runners and can be difficult to remove. Despite Nandina toxicity, the berries can be left on the plants for birds to harvest in late winter.
Spent berry stalks can be snapped off by hand in spring. Due to the occurring phytochemicals this plant is used in rabbit and javelina resistant landscape plantings. Nandina is derived from the Japanese vernacular name, ナンテン, pronounced ‘nanten’. Domestica means ‘domesticated’, or ‘of the household’. Huxley, A. ed.. New RHS Dictionary of Gardening 3: 284–285. Macmillan. Flora of North America: Nandina domestica Nandina domestica database Nandina domestica information Heavenly Bamboo information and resources
Senescence
Senescence or biological aging is the gradual deterioration of functional characteristics. The word senescence can refer either to senescence of the whole organism. Organismal senescence involves an increase in death rates and/or a decrease in fecundity with increasing age, at least in the part of an organism's life cycle. Senescence is the inevitable fate of all multicellular organisms with germ-soma separation, but it can be delayed; the discovery, in 1934, that calorie restriction can extend lifespan by 50% in rats, the existence of species having negligible senescence and immortal organisms such as Hydra, have motivated research into delaying senescence and thus age-related diseases. Rare human mutations can cause accelerated aging diseases. Environmental factors may affect aging, for example, overexposure to ultraviolet radiation accelerates skin aging. Different parts of the body may age at different rates. Two organisms of the same species can age at different rates, making biological aging and chronological aging distinct concepts.
There are a number of hypotheses as to. Organismal senescence is the aging of whole organisms. Actuarial senescence can be defined as an increase in mortality and/or a decrease in fecundity with age; the Gompertz–Makeham law of mortality says that that the age-dependent component of the mortality rate increases exponentially with age. In 2013, a group of scientists defined nine hallmarks of aging that are common between organisms with emphasis on mammals: genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, altered intercellular communication. Aging is characterized by the declining ability to respond to stress, increased homeostatic imbalance, increased risk of aging-associated diseases including cancer and heart disease. Aging has been defined as "a progressive deterioration of physiological function, an intrinsic age-related process of loss of viability and increase in vulnerability."The environment induces damage at various levels, e.g. damage to DNA, damage to tissues and cells by oxygen radicals, some of this damage is not repaired and thus accumulates with time.
Cloning from somatic cells rather than germ cells may begin life with a higher initial load of damage. Dolly the sheep died young from a contagious lung disease, but data on an entire population of cloned individuals would be necessary to measure mortality rates and quantify aging; the evolutionary theorist George Williams wrote, "It is remarkable that after a miraculous feat of morphogenesis, a complex metazoan should be unable to perform the much simpler task of maintaining what is formed." Different speeds with which mortality increases with age correspond to different maximum life span among species. For example, a mouse is elderly at 3 years. All organisms senesce, including bacteria which have asymmetries between "mother" and "daughter" cells upon cell division, with the mother cell experiencing aging, while the daughter is rejuvenated. There is negligible senescence such as the genus Hydra. Planarian flatworms have "apparently limitless telomere regenerative capacity fueled by a population of proliferative adult stem cells."
These planarians are not biologically immortal, but rather their death rate increases with age. Some species exhibit "negative senescence", in which reproduction capability increases or is stable, mortality falls, with age, resulting from the advantages of increased body size with age. Natural selection can support lethal and harmful alleles, if their effects are felt after reproduction; the geneticist J. B. S. Haldane wondered why the dominant mutation that causes Huntington's disease remained in the population, why natural selection had not eliminated it; the onset of this neurological disease is at age 45. Haldane assumed that, in human prehistory, few survived until age 45. Since few were alive at older ages and their contribution to the next generation was therefore small relative to the large cohorts of younger age groups, the force of selection against such late-acting deleterious mutations was correspondingly small. Therefore, a genetic load of late-acting deleterious mutations could be substantial at mutation-selection balance.
This concept came to be known as the selection shadow. Peter Medawar formalised this observation in his mutation accumulation theory of aging. "The force of natural selection weakens with increasing age—even in a theoretically immortal population, provided only that it is exposed to real hazards of mortality. If a genetic disaster... happens late enough in individual life, its consequences may be unimportant". The'real hazards of mortality' such as predation and accidents, are known'extrinsic mortality', mean that a population with negligible senescence will have fewer individuals alive in older age groups. Another evolutionary theory of aging was proposed by George C. Williams and involves antagonistic pleiotropy. A single gene may affect multiple traits; some traits that increase fitness early in life may have negative effects in life. But, because many more individuals are alive at young ages than at old ages small positive effects early can be selected for, large negative effects may be weakly selected against.
Williams suggested the following example: Perhaps a gene codes for calcium deposition in bones, which promotes juvenile survival and will therefore be favored by natural selection.
Dicotyledon
The dicotyledons known as dicots, are one of the two groups into which all the flowering plants or angiosperms were divided. The name refers to one of the typical characteristics of the group, namely that the seed has two embryonic leaves or cotyledons. There are around 200,000 species within this group; the other group of flowering plants were called monocotyledons or monocots having one cotyledon. These two groups formed the two divisions of the flowering plants. From the 1990s onwards, molecular phylogenetic research confirmed what had been suspected, namely that dicotyledons are not a group made up of all the descendants of a common ancestor. Rather, a number of lineages, such as the magnoliids and groups now collectively known as the basal angiosperms, diverged earlier than the monocots did; the traditional dicots are thus a paraphyletic group. The largest clade of the dicotyledons are known as the eudicots, they are distinguished from all other flowering plants by the structure of their pollen.
Other dicotyledons and monocotyledons have monosulcate pollen, or forms derived from it, whereas eudicots have tricolpate pollen, or derived forms, the pollen having three or more pores set in furrows called colpi. Aside from cotyledon number, other broad differences have been noted between monocots and dicots, although these have proven to be differences between monocots and eudicots. Many early-diverging dicot groups have "monocot" characteristics such as scattered vascular bundles, trimerous flowers, non-tricolpate pollen. In addition, some monocots have dicot characteristics such as reticulated leaf veins. Traditionally the dicots have been called the Dicotyledones, at any rank. If treated as a class, as in the Cronquist system, they could be called the Magnoliopsida after the type genus Magnolia. In some schemes, the eudicots were treated as a separate class, the Rosopsida, or as several separate classes; the remaining dicots may be kept in a single paraphyletic class, called Magnoliopsida, or further divided.
Some botanists prefer to retain the dicotyledons as a valid class, arguing its practicality and that it makes evolutionary sense. The following lists show the orders in the Angiosperm Phylogeny Group APG IV system traditionally called dicots, together with the older Cronquist system. In the Dahlgren and the Thorne systems, the subclass name Magnoliidae was used for the dicotyledons; this is the case in some of the systems derived from the Cronquist system. For each system, only the superorders are listed; the sequence of each system has been altered to pair corresponding taxa, although circumscription of superorders with the same name is not always the same. The Thorne system as depicted by Reveal is: Calyciflorae World list of dicot species via the Catalogue of Life Tree browser for dicot orders and genera with species counts and estimates via the Catalogue of Life
Etiolation
Etiolation is a process in flowering plants grown in partial or complete absence of light. It is characterized by weak stems; the development of seedlings in the dark is known as "skotomorphogenesis" and leads to etiolated seedlings. Etiolation increases the likelihood that a plant will reach a light source from under the soil, leaf litter, or shade from competing plants; the growing tips are attracted to light and will elongate towards it. The pale color results from a lack of chlorophyll; some of the changes that occur leaves. De-etiolation is the transition of seedlings from below-ground growth to above-ground growth form. Elongation is controlled by the plant hormones called auxins, which are produced by the growing tip to maintain apical dominance. Auxin diffuses, is transported, downwards from the tip, with effects including suppressing growth of lateral buds. Auxins are active in light. Chloroplasts that have not been exposed to light are called etioplasts. De-etiolation, is a series of physiological and biochemical changes a plant shoot undergoes when emerging from the ground or in response to light after a period of insufficient light exposure.
This process is known informally as greening. These changes that are triggered in the plants shoots or formed leaves and stems occur in preparation for photosynthesis; some of the changes that occur include Inhibition of hypocotyl lengthening. Stimulation of cotyledon expansion. Opening of the apical hook, see Seedling's etiolation for details. Stimulation of synthesis of anthocyanins. Stimulation of chloroplasts development from etioplasts; this process is regulated by the exposure of various photoreceptor pigments to light. Phytochrome A and phytochrome B both respond to an increasing proportion of red light to far-red light which occurs when the shoot comes out into the open. Cryptochrome 1 responds to increasing amounts of blue light. Blanching – a technique for growing vegetables that induces etoliation to produce more delicate vegetables Etiolation - video footage and narration Etiolation
Down feather
The down of birds is a layer of fine feathers found under the tougher exterior feathers. Young birds are clad only in down. Powder down is a specialized type of down found only in a few groups of birds. Down is a fine thermal insulator and padding, used in goods such as jackets, bedding and sleeping bags; the discovery of feathers trapped in ancient amber suggests that some species of dinosaur may have possessed down-like feathers. The word down comes from the Old Norse word dúnn, which had the same meaning as its modern equivalent; the down feather is considered to be the most "straightforward" of all feather types. It has a short or vestigial rachis, few barbs, barbules that lack hooks. There are three types of down: body down and powder down. Natal down is the layer of down feathers that cover most birds at some point in their early development. Precocial nestlings are covered with a layer of down when they hatch, while altricial nestlings develop their down layer within days or weeks of hatching.
Megapode hatchlings are the sole exception. Body down is a layer of small, fluffy feathers that lie underneath the outer contour feathers on a bird's body. Powder down, or pulviplumes, is a special type of down that occurs in a few groups of unrelated birds. In some species, the tips of the barbules on powder down feathers disintegrate, forming fine particles of keratin, which appear as a powder, or "feather dust", among the feathers; these feathers are not molted. In other species, powder grains come from cells; these specialized feathers are scattered among ordinary down feathers, though in some species, they occur in clusters. All parrots have powder down, with some species producing copious amounts, it is found in tinamous and herons. The dust produced from powder down feathers is a known allergen in humans; the loose structure of down feathers traps air, which helps to insulate the bird against heat loss and contributes to the buoyancy of waterbirds. Species that experience annual temperature fluctuations have more down feathers following their autumn moult.
There is some evidence that down feathers may help to decrease the incidence of nestling cannibalism among some colonially nesting species, as the stiffness of the feathers make the young more difficult to swallow. Pollutants can reduce the efficiency of these functions; when oiled, for example, down feathers mat and clump together, which breaks down the bird's insulation and allows water to reach the skin. Female wildfowl use down feathers plucked from their own breasts to line their scrape nests; this process performs the dual function of helping to insulate the eggs and exposing the female's brood pouch—an area of bare skin, rich in blood vessels, which transmits heat efficiently. Of the various items birds use to line their nests, down feathers provide the most effective insulation, though only when dry. Down may help camouflage the eggs when the female is away from the nest as the birds draw the feathers over their eggs before leaving; because a bird can eliminate heavy metals in its feathers and because feathers can be collected non-invasively and stored indefinitely, down feathers can be used to check for evidence of metal contamination in the bird's environment.
Studies have shown a high level of correlation between the level of metal contamination in a bird's diet and the level found in its feathers, with the proportion of the chemicals found in its feathers remaining constant. Mutations in the genes that control the formation of down feathers have been recorded in a German White Leghorn flock. Although the elements of a normal down feather are present, a hyperkeratosis of the feather's horny sheath after 16–17 days of incubation results in the sheath not splitting as it should during the final stages of the feather's growth; because of that abnormal splitting, the bird's down appears to be matted. Down feathers were used by indigenous North Americans for religious ceremonies and as powerful symbols. In the stories of some cultures, the down feathers of an eagle were important gifts given by the bird to the story's hero. In the Ghost Dance, a religious movement that became widespread among the Plains Indians, each dancer held a painted feather, tipped with a down feather painted with another color.
Zuni prayer sticks were made using eagle down. While eagle feathers belonged to the Sun Priest, who planted them to the sun, other priests could use them if rain was needed, as the down is said to suggest "fleecy clouds that gather on the horizon before rain"; the Hopi rubbed eagle down feathers over rattlesnakes being collected for their Snake Dances, in an effort to soothe and calm the reptiles. For centuries, humans across the globe have used down feathers for insulation. Russian documents from the 1600s list "bird down" among the goods sold to Dutch merchants, communities in northern Norway began protecting the nests of eider ducks as early as 1890. Eiders are still "farmed" by people in Iceland and Siberia; the birds are provided with nest sites and protected from predators, down is collected intermittently during the nesting season without harming the nests or female ducks. The first collection is made halfway through the incubation per
Monocotyledon
Monocotyledons referred to as monocots, are flowering plants whose seeds contain only one embryonic leaf, or cotyledon. They constitute one of the major groups into which the flowering plants have traditionally been divided, the rest of the flowering plants having two cotyledons and therefore classified as dicotyledons, or dicots. However, molecular phylogenetic research has shown that while the monocots form a monophyletic group or clade, the dicots do not. Monocots have always been recognized as a group, but with various taxonomic ranks and under several different names; the APG III system of 2009 recognises a clade called "monocots" but does not assign it to a taxonomic rank. The monocots include about 60,000 species; the largest family in this group by number of species are the orchids, with more than 20,000 species. About half as many species belong to the true grasses, which are economically the most important family of monocots. In agriculture the majority of the biomass produced; these include not only major grains, but forage grasses, sugar cane, the bamboos.
Other economically important monocot crops include various palms and plantains, gingers and their relatives and cardamom, pineapple, water chestnut, leeks and garlic. Many houseplants are monocot epiphytes. Additionally most of the horticultural bulbs, plants cultivated for their blooms, such as lilies, irises, cannas and tulips, are monocots; the monocots or monocotyledons have, as the name implies, a single cotyledon, or embryonic leaf, in their seeds. This feature was used to contrast the monocots with the dicotyledons or dicots which have two cotyledons. From a diagnostic point of view the number of cotyledons is neither a useful characteristic, nor is it reliable; the single cotyledon is only one of a number of modifications of the body plan of the ancestral monocotyledons, whose adaptive advantages are poorly understood, but may have been related to adaption to aquatic habitats, prior to radiation to terrestrial habitats. Monocots are sufficiently distinctive that there has been disagreement as to membership of this group, despite considerable diversity in terms of external morphology.
However, morphological features that reliably characterise major clades are rare. Thus monocots are distinguishable from other angiosperms both in terms of their uniformity and diversity. On the one hand the organisation of the shoots, leaf structure and floral configuration are more uniform than in the remaining angiosperms, yet within these constraints a wealth of diversity exists, indicating a high degree of evolutionary success. Monocot diversity includes perennial geophytes such as ornamental flowers including and succulent epiphytes, all in the lilioid monocots, major cereal grains in the grass family and forage grasses as well as woody tree-like palm trees, bamboo and bromeliads, bananas and ginger in the commelinid monocots, as well as both emergent and aroids, as well as floating or submerged aquatic plants such as seagrass. Organisation and life formsThe most important distinction is their growth pattern, lacking a lateral meristem that allows for continual growth in diameter with height, therefore this characteristic is a basic limitation in shoot construction.
Although herbaceous, some arboraceous monocots reach great height and mass. The latter include agaves, palms and bamboos; this creates challenges in water transport. Some, such as species of Yucca, develop anomalous secondary growth, while palm trees utilise an anomalous primary growth form described as establishment growth; the axis undergoes primary thickening, that progresses from internode to internode, resulting in a typical inverted conical shape of the basal primary axis. The limited conductivity contributes to limited branching of the stems. Despite these limitations a wide variety of adaptive growth forms has resulted from epiphytic orchids and bromeliads to submarine Alismatales and mycotrophic Burmanniaceae and Triuridaceae. Other forms of adaptation include the climbing vines of Araceae which use negative phototropism to locate host trees, while some palms such as Calamus manan produce the longest shoots in the plant kingdom, up to 185 m long. Other monocots Poales, have adopted a therophyte life form.
LeavesThe cotyledon, the primordial Angiosperm leaf consists of a proximal leaf base or hypophyll and a distal hyperphyll. In monocots the hypophyll tends to be the dominant part in contrast to other angiosperms. From these, considerable diversity arises. Mature monocot leaves are narrow and linear, forming a sheath
Photomorphogenesis
In developmental biology, photomorphogenesis is light-mediated development, where plant growth patterns respond to the light spectrum. This is a separate process from photosynthesis where light is used as a source of energy. Phytochromes and phototropins are photochromic sensory receptors that restrict the photomorphogenic effect of light to the UV-A, UV-B, red portions of the electromagnetic spectrum; the photomorphogenesis of plants is studied by using frequency-controlled light sources to grow the plants. There are at least three stages of plant development where photomorphogenesis occurs: seed germination, seedling development, the switch from the vegetative to the flowering stage. Most research on photomorphogenesis comes from plants, it occurs in several kingdoms: Fungi, Monera and Plantae. Theophrastus of Eresus may have been the first to write about photomorphogenesis, he described the different wood qualities of fir trees grown in different levels of light the result of the photomorphogenic "shade-avoidance" effect.
In 1686, John Ray wrote "Historia Plantarum". Charles Bonnet introduced the term "etiolement" to the scientific literature in 1754 when describing his experiments, commenting that the term was in use by gardeners. Light has profound effects on the development of plants; the most striking effects of light are observed when a germinating seedling emerges from the soil and is exposed to light for the first time. The seedling radicle emerges first from the seed, the shoot appears as the root becomes established. With growth of the shoot there is increased secondary root formation and branching. In this coordinated progression of developmental responses are early manifestations of correlative growth phenomena where the root affects the growth of the shoot and vice versa. To a large degree, the growth responses are hormone mediated. In the absence of light, plants develop an etiolated growth pattern. Etiolation of the seedling causes it to become elongated, which may facilitate it emerging from the soil.
A seedling that emerges in darkness follows a developmental program known as skotomorphogenesis, characterized by etiolation. Upon exposure to light, the seedling switches to photomorphogenesis. There are differences when comparing dark-grown and light-grown seedlings Etiolated characteristics: Distinct apical hook or coleoptile No leaf growth No chlorophyll Rapid stem elongation Limited radial expansion of stem Limited root elongation Limited production of lateral rootsDe-etiolated characteristics: Apical hook opens or coleoptile splits open Leaf growth promoted Chlorophyll produced Stem elongation suppressed Radial expansion of stem Root elongation promoted Lateral root development acceleratedThe developmental changes characteristic of photomorphogenesis shown by de-etiolated seedlings, are induced by light; some plants rely on light signals to determine when to switch from the vegetative to the flowering stage of plant development. This type of photomorphogenesis is known as photoperiodism and involves using red photoreceptors to determine the daylength.
As a result, photoperiodic plants only start making flowers when the days have reached a "critical daylength," allowing these plants to initiate their flowering period according to the time of year. For example, "long day" plants need long days to start flowering, "short day" plants need to experience short days before they will start making flowers. Photoperiodism has an effect on vegetative growth, including on bud dormancy in perennial plants, though this is not as well-documented as the effect of photoperiodism on the switch to the flowering stage. Plants are responsive to wavelengths of light in the blue and far-red regions of the spectrum through the action of several different photosensory systems; the photoreceptors for red and far-red wavelengths are known as phytochromes. There are at least 5 members of the phytochrome family of photoreceptors. There are several blue light photoreceptors known as cryptochromes; the combination of phytochromes and cryptochromes mediate growth and the flowering of plants in response to red light, far-red light, blue light.
Plants use phytochrome to respond to red and far-red wavelengths. Phytochromes are signaling proteins that promote photomorphogenesis in response to red light and far-red light. Phytochrome is the only known photoreceptor that absorbs light in the red/far red spectrum of light and only for photosensory purposes. Phytochromes are proteins with a light absorbing pigment attached called a chromophore; the chromophore is a linear tetrapyrrole called phytochromobilin. There are two forms of phytochromes: red light absorbing, Pr, far-red light absorbing, Pfr. Pfr, the active form of phytochromes, can be reverted to Pr, the inactive form by inducing darkness or more by irradiation by far-red light; the phytochrome apoprotein, a protein that together with a prosthetic group forms a particular biochemical molecule such as a hormone or enzyme, is synthesized in the Pr form. Upon binding the chromophore, the holoprotein, an apoprotein combined with its prosthetic group, becomes sensitive to light. If it absorbs red light it will change conformation to the biologically active Pfr form.
The Pfr form can switch back to the Pr form. The Pfr promotes and regulates photomorphogenesis in response to FR light, whereas Pr regulates de-etiolation in response to R light. Most plants
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