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Leaf curl

Leaf curl is a plantdisease caused by a fungus (Taphrina deformans, genus Taphrina) orvirus (especially genus Begomovirus of the family Geminiviridae) and characterized by curling of leaves. Although all leaf curl occurring in different plants (usually only citrus plants) is relatively the same, one of the most notable types is peach leaf curl, caused by the fungus Taphrina deformans.Taphrina deformansbelongs to the subclassProtoascomycetes. Leaf curl is found in America, Europe, Asia, Africa, Australia, and New Zealand . It was first introduced in America in 1852 and has now spread all over the country .

Problems with Leaf Curl

'Leaf curl has caused many damages over the years. It makes the amount of leaves and fruit produced by trees significantly lower. It has caused many trees to die. The disease also costs the United States 2.5 to 3 million dollars annually . However, it is believed that this disease is preventable from such serious effects. If the correct sprays (usually lime sulfur) are used correctly, a 98% yield of healthy fruit is obtained. If trees are not sprayed with specific chemicals early enough, and if the tree is treated after the host tissue is infected, treatment is ineffective.


Leaf Curl has characteristics that are very differentiating and easily noticeable. Diseased leaves can usually be picked out early after leaving the bud due to their reddish color and arched shape. As the leaves develop, they appear distorted and fold their tips backwards. Diseased leaves are usually thicker and softer than the normal, unharmed leaves. The colors of the leaves are also unique. Instead of the normal green spring leaves, the colors turn yellow, followed by purple, until finally a whitish bloom covers each leaf. Twigs may show signs of sickness, such as being black in color and swollen. Fruit can be affected, showing a reddish color . Infected leaves fall early. The tree may produce a second crop of leaves that is never diseased, because the fungus cannot survive at the higher temperatures in late spring and early summer. The fungus prefers the high humidity in the early spring because it permits spores to germinate . If the tree is infected for consecutive years death may occur .

Causes of Leaf Curl

When a virus is the cause of leaf curl in a plant, usually an insect will carry the virus to the plant. This is such the case in sweet potato leaf curl, carried by the sweet potato whitefly . The whitefly also has been found to transport the leaf curl virus to tomatoes. This has been seen since 1997 in Florida, and has since spread to other southern states. The virus was recently seen in South Carolina, and with the abundance of whiteflies in the state, has the potential to spread out of the southeastern United States. The Geminiviridae virus has also been seen to spread by the transport of nursery soils. The virus appears to stay in soil, and when a new crop is planted, affects the new host.

When a whitefly (and some other carriers of viruses) eats leaves on an infected plant, the virus enters its saliva and is spread when the fly eats at a healthy tree. This explains the rapid amount of trees infected in a given area .

When a fungus causes the sickness, a different process occurs. The fungus (Taphrina deformans) causes the whitish bloom that covers each leaf as infection progresses. This color is made of asci that break through the cuticle of the leaf. One asci consists of eight ascospores that create conidia, which are ejected in early summer and moved by methods of rain and wind. It is believed that this fungus survives the winter by staying on the surface of the new host plant, such as on bark or buds . In the spring, new buds are affected by the conidia as the leaves come out of the buds. The fungus produces the ascospores on the surface of the already infected leaves. Often the disease does not occur every year due to the variances in temperature and weather from year to year. The fungus has higher infection rates following cooler winters, has optimal temperatures for infection, and requires rain..

Other common diseases caused by ascomycetes include: the Dutch Elm Disease, Chestnut Blight, Leaf Spot, and Ergot .

Control of the Disease

Although other methods are under investigation, spraying the leaves with fungicides are the most common and efficient control of the disease. It is important for spraying to occur well before budding. Different areas in climates depict the type of fungicide used and how often, since experiments have shown that the fungi are temperature dependent. Some fungicides commonly used include, among other things, copper based mixtures and lime sulfurs.

If a plant appears to have symptoms of leaf curl, precautions can be taken to maximize the crops for that spring. The trees are often treated with nitrogen and excess water to minimize stress on the tree. So the tree can focus on producing good peaches, thinning the tree out might also help. It would be advantageous to take away the infected leaves and fruit after they fall to the ground so that next years tree might not get infected. Fungicide might also be used before winter on the tree .

Future of the Disease

Scientists are on a mission to stop leaf curl infections. There have been observations that some crops have certain characteristics that make them not susceptible to the virus or fungus, even ones of the same species that are infected in other parts of the world. Experiments are being conducted and hopefully less susceptible crops will be able to be produced and stop the infection.

Due to millions of dollars of debt in the U.S. Agriculture Department in 1992, universities, state departments, and the USDA adopted a national plan of research and action against the internationalindustry trade group of airlines headquartered in Montreal, Canada, where the International Civil Aviation Organization is also headquartered.

IATA's mission is to represent, lead, and serve the airline industry. IATA represents some 230 airlines comprising 93% of scheduled international air traffic. The Director General and Chief Executive Officer is Giovanni Bisignani. Currently, IATA is present in over 150 countries covered through 101 offices around the globe.

The IATA Head Office are located at 800 Place Victoria (Montreal Stock Exchange Tower) in Montreal since 1977 (having been located at Central Station (Montreal) since its founding) and the executive offices are at the Geneva Airport in Switzerland.


IATA was formed on 19 April 1945, in Havana, Cuba. It is the successor to the International Air Traffic Association, founded in The Hague in 1919, the year of the world's first international scheduled services. At its founding, IATA had 57 members from 31 nations, mostly in Europe and North America. Today it has about 230 members from more than 140 nations in every part of the world.


IATA’s stated mission is to represent, lead and serve the airline industry.All the Airline rules and regulations are defined by IATA.The main aim of IATA is to provide safe and secure transportation to its passengers.

Its stated aims and objectives are as follows:

• to promote safe, regular and economical air transport for the benefit of the people of the world, to foster air commerce and study the problems connected therewith • to promote means for collaboration among air transport enterprises engaged directly or indirectly in international air transport service • to cooperate with ICAO and other international organisations There is always close association and dialogue between ICAO and IATA. We shall now look at the organisation of IATA. Organisation In order to fulfil its aims and objectives IATA is divided into various departments, each with a specific role to fulfil. We shall be looking at the roles of some of these departments. Traffic Department• Provides a forum for traffic coordination discussions • Services as a central source of traffic information for publishers and members • Lists and verifies services of cargo and travel agents worldwide on behalf of the member airlines • Coordinates training programmes for cargo and travel agents • Arranges centralised billing and reporting of agents' sales • Provides a forum for airlines to resolve scheduling problems • Helps represent the industry on airmail issues • Promotes awareness programmes to combat fraud Legal Department• Provides professional legal advise and interpretations to individual members as required from an airline perspective • Distributes and publishes information on legal or regulatory issues of industry-wide interest and importance • Formulates industry positions vis-à-vis bodies like ICAO, the European Community and individual governments

Technical Department• Develops standards to help maximise flight safety, in cooperation with governments, airlines and manufacturers • Advocates airline positions on operational needs • Provides guidance on medical standards for crew, health and hygiene; sets standards for catering and seeks to facilitate travel for all passengers including the handicapped • Assimilates safety statistics and conducts security and safety related seminars • Liaises with governments and international organisations on problems such as drugs smuggling, terrorism, the checking of international documents such as cargo air waybills and passenger ticket fraud

Government and Industry Affairs Department• Lobbies government and international organisations to promote and defend the interests of scheduled airlines • Represents IATA on a regional level and also supports efforts of regional airline organisations on behalf of their member airlines to maintain good working relations with governments • Runs low cost training programmes for staff from developing nations' airlines and related projects • Provides after sales service to new members • Analyses political and economic trends likely to affect airline operations, distributes such information and helps define industry Industry Automotive and Financial Services Department• Operates an industry clearing house handling in excess of USD 25 billion annually • Oversees the functioning of interline agreements designed to offer cargo shipments and passenger convenience • Maintains standard operation criteria and procedures to speed the flow of passengers, baggage and cargo and publishes various types of industry reference material • Assembles, analyses and publishes comparative statistical data for use by airline managements in their planning

Public Relations Department• Represents and defends collective airline interests vis-à-vis the media, consumer groups and the public at large • Serves as a channel for airlines of sizes to benefit from each others' public relations and expertise • Helps market IATA products • Maintains information flow to members

We thus see that various departments of IATA, from their offices at Montréal, Geneva and Singapore do yeomen service not just to the airline industry but also to governments and various related industries. Some of these services are a great help to the Freight Forwarding Industry and other communities. Students too can gain a great deal from IATA's programmes. IATA Cargo and Passenger Agency Programmes Within the Traffic Department there is a specialised section dealing with cargo and travel agency matters. This section is called the IATA Agency Administration Department whose task is to oversee the running of IATA Cargo and Passenger Agency Programmes. Among its diverse functions are: • Listing and certifying service of cargo and travel agents • Coordinating training programmes for cargo and travel agents • Arranging for centralised billing and reporting of cargo and travel agents' sales We shall look at each of these programmes and these functions. The Agency Accreditation Programme Airlines, world over, carry cargo from airport to airport. There are services to be provided before and after carriage. Similarly, airlines need distribution channels beyond their own sales network to sell and market their products worldwide. This need of airlines led to the evolution of the IATA agency. When we discuss about intermediaries we shall look at the details of the functions and working of an IATA agency. The IATA Agency Programme has been steadily built up over a period of almost 60 years. Its mai

Internal energy

In thermodynamics, the internal energy is the total energy contained by a thermodynamic system. It is the energy necessary to create the system, but excludes the energy to displace the system's surroundings, any energy associated with a move as a whole, or due to external force fields. Internal energy has two major components, kinetic energy and potential energy. The kinetic energy is due to the motion of the system's particles (translations, rotations, vibrations), and the potential energy is associated with the static constituents of matter, static electric energy of atoms within molecules or crystals, and the static energy of chemical bonds. The internal energy of a system can be changed by heating the system or by doing work on it; the first law of thermodynamics states that the increase in internal energy is equal to the total heat added and work done. If the system is isolated, its internal energy cannot change.

For practical considerations in thermodynamics or engineering it is rarely necessary, nor convenient, to consider all energies belonging to the total intrinsic energy of a sample system, such as the energy given by the equivalence of mass. Typically, descriptions only include components relevant to the system under study. Thermodynamics is chiefly concerned only with changes of the internal energy.

The internal energy is a state function of a system, because its value depends only on the current state of the system and not on the path taken or process undergone to arrive at this state. It is an extensive quantity. The SI unit of energy is the joule ( J ). Sometimes a corresponding intensivethermodynamic property called specific internal energy is defined, which is internal energy per a unit of mass of the system in question. As such, the SI unit of specific internal energy is joules/kilogram (J/kg). If intensive internal energy is expressed on a per mole basis, then it is referred to as molar internal energy and the unit is joule/mole (J/mol).

From the standpoint of statistical mechanics, the internal energy is equal to the ensemble average of the total energy of the system. It is also called intrinsic energy.

Description and definition

The internal energy (U) is the sum of all forms of energy (Ei) intrinsic to a thermodynamic system:

U = \sum_i E_i \!

It is the energy needed to create the system. It may be divided into potential energy (Upot) and kinetic energy (Ukin) components:

U = U_{pot} + U_{kin} \!

The kinetic energy of a system arises as the sum of the motions of all the system's particles, whether it be the motion of atoms, molecules, atomic nuclei, electrons, or other particles. The potential energy includes all energies given by the mass of particles, by the chemical composition, i.e. the chemical energy stored in chemical bonds having the potential to undergo chemical reactions, the nuclear energy stored by the configuration of protons, neutrons, and other elementary particles in atomic nuclei, and the physical force fields within the system, such as due to internal induced electric or magneticdipolemoment, as well as the energy of deformation of solids (stress-strain).

Internal energy does not include the energy due to motion of a system as a whole. It further excludes any kinetic or potential energy a body may have because of its location in external gravitational, electrostatic, or electromagnetic force fields.

For practical considerations in thermodynamics or engineering it is rarely necessary, convenient, nor even possible, to consider all energies belonging to the total intrinsic energy of a sample system, such as the energy given by the equivalence of mass. Typically, descriptions only include components relevant to the system under study. Indeed in most systems under consideration, especially through thermodynamics, it is impossible to calculate the total internal energy. Therefore, a convenient null reference point may be chosen for the internal energy.

The internal energy is an extensive property: it depends on the size of the system, or on the amount of substance it contains.

At any temperature greater than absolute zero, potential energy and kinetic energy are constantly exchanged into one another, but the sum remains constant in an isolated system (cf. table). In the classical picture of thermodynamics, kinetic energy vanishes at zero temperature and the internal energy is purely potential energy. However, quantum mechanics has demonstrated that even at zero temperature particles maintain a residual energy of motion, the From Yahoo Answers

Question:help please ,cereally people ,i need to sleep ,also I need to finish other stuff too ,please have some mercy .

Answers:There are several levels of structure in studying a leaf. A leaf attached to the tree at a node. The stalk that attaches the leaf to the tree is the petiole which extend into the midrib of the leaf called the rachis. There may be a pair of extensions from the base of the petiole called stiplules. Many veins branch off the rachis. The flat part of the leaf is called the blade. There are many shapes of leaves and different margins. If you take a section of the leaf, you would find the following tissue layers from top to the bottom of the leaf: upper epidermis covered with a waxy cuticle, palisade mesophyll and spongy mesophyll in which the photosynthesis occurs, a lower epidermis perforated with numerous holes called stomata. The stomata are surrounded by guard cells that can open and close. The stomata allow gas exchange (carbon dioxide in and oxygen and water vapor out). There will be cross sections of veins as well. In the vein, there will be xylem carrying water and minerals at the top of the vein with phloem on the bottom of the vein. The structure of the leaf allows for maximum absorption of sunlight for photosynthesis.

Question:here is a stem and leaf plot for the ages of students in a class: stem -------Leaf 1 ------------8 8 8 9 9 9 9 9 2 ------------0 0 0 0 0 1 3 4 ------------2 5 Does this mean that there are three 18 year olds, five 19 year olds, five 20 year olds, one 21 year old, one 42 year old, and one 45 year old? what is the point of this?

Answers:Yes that's how it works, it does seem a bit pointless I know. Its so you can see it grouped, then it is easier to find the mean, median, mode and range. The stem and leaf diagram is formed by splitting the numbers into parts.

Question:i have a jade plant and have heard that you can grow another with the leaf. But first i need to callus it. How do i do that?

Answers:Cut a leaf off at its base with a sharp knife and the callus part is leaving it to dry out for a couple of days ( a callus forms over the cut) before planting it in soil,or it'll tend to rot....done it a few times and they root easily..

Question:grrr I have a homework on photosythesis it only says LEAF STRUCTURE and I dont know if it's internal or external structure!!!

Answers:Do both! External - flat & thin, absorb lot of light, rapid diffusion of gases. Internal - most chloroplasts in palisade cells, closer to light, palisade cells closely packed, shape of palisade cells transparent cell walls air spaces in spongy mesophyll.

From Youtube

How the structure of the leaf relates to its adaptations for photosynthisis :External features The waxy cuticle at the top of the leaf is transparent, allowing light to enter for photosynthesis. It also stops transpiration from happening through the leaf, other than in the stomata. The upper epidermal cells are also transparent to allow light in to reach the chloroplasts for photosynthesis. The lower epidermis has stomata, which allow gaseous exchange to occur. Gaseous exchange being the intake of CO2 and the release of O2, which is essential for photosynthesis. The leaf is thin, and has a very large surface area - making it ideal for diffusion and absorbsion. The larger the surface area, the more sunlight can be absorbed. The leaf is also thin so that the mesophyll cells are closer to the surface - reducing the diffusion distance of CO2 from the surroundings to the mesophyll cells. Internal features Vascular Tissue This is to do with the xylem and the phloem. The xylem is always at the top of the leaf, and the phloem at the bottom because the xylem transports water(needed for photosynthesis) to the leaf cells, and diffuses into the chloroplasts.The phloem transports food from the mesophyll cells to the rest of the plant. The xylem and phloem are vascular tissue that are situated in the leaf vein. The vein is supported by fibres(sclerenchyma), which keep the shape of the leaf, flat. Mesophyll There are two main types of Mesophyll cells, the palisade and spongy cells.Palisade - contain the most chloroplast, and are at the top of the leaf. Are ...

Maple Leaf Rag - Scott Joplin :In this well known piece I have programed the keyboard to play a honky tonk piano with a dixie rhythm at 75 crotchet beats per minute. I have taken off the weighted keys but used a sustain pedal to create a more legato effect. The hardest part of this piece is the trio section with wide octave leaps in the LH. It's important to practise slowly and learning from memory is a great help when performing the stride bass.