Greenhouse

A greenhouse (also called a glasshouse or hothouse) is a building where plants are cultivated. Explanation A greenhouse is structure with a glass or plastic roof and frequently glass or plastic walls; it heats up because incoming solar radiation from the sun warms plants, soil, and other things inside the building. Air warmed by the heat from hot interior surfaces is retained in the building by the roof and wall. These structures range in size from small sheds to very large buildings. The glass used for a greenhouse works as a selective transmission medium for different spectral frequencies, and its effect is to trap energy within the greenhouse, which heats both the plants and the ground inside it. This warms the air near the ground, and this air is prevented from rising and flowing away, in addition to the fact that infrared radiation cannot pass through the greenhouse glass. This can be demonstrated by opening a small window near the roof of a greenhouse: the temperature drops considerably. This principle is the basis of the autovent automatic cooling system. Greenhouses thus work by trapping electromagnetic radiation and preventing convection. Miniature greenhouses are known as a Cold frame. Uses Greenhouse effects are often used for growing flowers, vegetables, fruits, and tobacco plants. Bumblebees are the pollinators of choice for most greenhouse pollination, although other types of bees have been used, as well as artificial pollination. Besides tobacco, many vegetables and flowers are grown in greenhouses in late winter and early spring, then transplanted outside as the weather warms. Started plants are usually available for gardeners in farmers' markets at transplanting time.

The closed environment of a greenhouse has its own unique requirements, compared with outdoor production. Pests and diseases, and extremes of heat and humidity, have to be controlled, and irrigation is necessary to provide water. Significant inputs of heat and light may be required, particularly with winter production of warm-weather vegetables. Special greenhouse varieties of certain crops, like tomatoes, are generally used for commercial production.

Greenhouses are increasingly important in the food supply of high latitude countries. The largest greenhouse complex in the world is at Leamington, Ontario (close to Canada's most southern point) where about 200 acres (0.8 km²) of tomatoes are entirely grown under glass. Greenhouses protect crops from too much heat or cold, shield plants from dust storms and blizzards, and help to keep out pests. Light and temperature control allows greenhouses to turn unarable land into arable land. Greenhouses can feed starving nations where crops can't survive in the harsh deserts and arctic wastes. Hydroponics can be used in greenhouses as well to make the most use of the interior space.. History The idea of growing plants in environmentally controlled areas has existed since Roman times. Doctors for the Roman emperor Tiberius prescribed him a cucumber daily. The Roman gardeners used artificial methods (similar to the greenhouse system) of growing to have it available for his table every day of the year. Cucumbers were planted in wheeled carts which were put in the sun daily, then taken inside to keep them warm at night. The cucumbers were stored under frames or in cucumber houses glazed with either oiled cloth known as "specularia" or with sheets of mica. (Pliny the Elder and Columella).

The first modern greenhouses were built in Italy in the sixteenth century to house the exotic plants that explorers brought back from the tropics. They were originally called giardini botanici (botanical gardens). The concept of greenhouses soon spread to the Netherlands and then England, along with the plants. Some of these early attempts required enormous amounts of work to close up at night or to winterize. There were serious problems with providing adequate and balanced heat in these early greenhouses. Jules Charles, a French botanist, is often credited with building the first practical modern greenhouse in Leiden, Holland to grow medicinal tropical plants.

Originally on the estates of the rich, with the growth of the science of botany greenhouses spread to the universities. The British some times called their greenhouses conservatories, since they conserved the plants. The French called their first greenhouses orangeries, since they were used to protect orange trees from freezing. As pineapples became popular pineries were built. Experimentation with the design of greenhouses continued during the Seventeenth Century in Europe as technology produced better glass and construction techniques improved. The greenhouse at the Palace of Versailles was an example of their size and elaborateness; it was more than 500 feet long, 42 feet wide, and 45 feet high.

In the nineteenth Century the largest greenhouses were built. The conservatory at Kew Gardens in England is a prime example of the Victorian greenhouse. Although intended for both horticultural and non-horticultural exhibition these included London's Crystal Palace, the New York Crystal Palace and Munich’s Glaspalast. Joseph Paxton, who had experimented with glass and iron in the creation of large greenhouses as the head gardener at Chatsworth, in Derbyshire, working for the Duke of Devonshire, designed and built the first, London's Crystal Palace. In Japan, the first greenhouse was built in 1880 by Samuel Cocking, a British merchant who exported herbs. In the Twentieth Century the geodesic dome was added to the many types of greenhouses. ( Original Source : Wikipedia Encyclopedia, Photo Source : Google Images )

Global Warming

( Original Source : Wikipedia Encyclopedia, Photo Source : Google Images )

Energy Portal
Global warming is the observed increase in the average temperature of the Earth's atmosphere and oceans in recent decades, and its projected continuation. Models referenced by the Intergovernmental Panel on Climate Change (IPCC) predict that global temperatures are likely to increase by 1.1 to 6.4 °C (2.0 to 11.5 °F) between 1990 and 2100. The uncertainty in this range results from both the difficulty of predicting the volume of future greenhouse gas emissions and uncertainty about climate sensitivity and feedback effects.

Global average near-surface atmospheric temperature rose 0.6 ± 0.2 °Celsius (1.1 ± 0.4 °Fahrenheit) in the 20th century. The prevailing scientific opinion on climate change is that "most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations", which leads to warming of the surface and lower atmosphere by increasing the greenhouse effect. Greenhouse gases are released by activities such as the burning of fossil fuels, land clearing, and agriculture. Other phenomena such as solar variation have had smaller but non-negligible effects on global temperature trends since 1950.

An increase in global temperatures can in turn cause other changes, including a rising sea level and changes in the amount and pattern of precipitation. These changes may increase the frequency and intensity of extreme weather events, such as floods, droughts, heat waves, hurricanes, and tornados. Other consequences include higher or lower agricultural yields, glacier retreat, reduced summer streamflows, species extinctions and increases in the ranges of disease vectors. Warming is expected to affect the number and magnitude of these events; however, it is difficult to connect particular events to global warming. Although most studies focus on the period up to 2100, even if no further greenhouse gases were released after this date, warming (and sea level) would be expected to continue to rise for more than a millenium, since CO2 has a long average atmospheric lifetime.

Remaining scientific uncertainties include the exact degree of climate change expected in the future, and especially how changes will vary from region to region across the globe. A hotly contested political and public debate has yet to be resolved, regarding whether anything should be done, and what could be cost-effectively done to reduce or reverse future warming, or to deal with the expected consequences. Most national governments have signed and ratified the Kyoto Protocol aimed at combatting global warming.

Bonsai

History It appears that the Chinese were the first to miniaturize container-grown trees around 200 AD. The art form may be derived from the practice of transporting medicinal plants in containers by healers. Its early focus was on the display of stylistic trunks in the shape of animals and mystic figures.

From China, the practice spread to Japan around the Heian period. During the Tokugawa period, landscape gardening attained new importance. Cultivation plants such as azalea and maples became a pastime of the wealthy. Growing dwarf plants in containers was also popular, but by modern bonsai standards the container plants of this period were inappropriately large.

The period term for dwarf potted trees was hachi-no-ki, "a tree in a pot." The term "bonsai" probably didn't come into use until the late 19th century during the Meiji period. Aesthetics

Japanese School The Japanese aesthetic is centred on the principle of "heaven and earth in one container", as a Japanese cliché has it. Three forces come together in a good bonsai: shin-zen-bi (真善美) or truth, essence and beauty.

Traditional subjects for bonsai include pine, maple, elm, flowering apricot, Japanese wisteria, juniper, flowering cherry, azalea and larch. The plants are grown outdoors and brought in to the tokonoma at special occasions when they most evoke the current season.

The Japanese bons are meant to evoke the essential spirit of the plant being used: in all cases, they must look natural and never show the intervention of human hands.

Techniques Shaping and dwarfing are accomplished through a few basic but precise techniques. The small size of the tree and the dwarfing of foliage are maintained through a consistent regimen of pruning of both the leaves and the roots. Various methods must be employed, as each species of tree exhibits different budding behavior. Additionally, some pruning must be done seasonally, as most trees require a dormancy period and do not grow roots or leaves at that time; improper pruning can weaken or kill the tree.

Most species suitable for bonsai can be shaped by wiring. Copper or aluminium wire is wrapped around branches and trunks, holding the branch in place until it eventually lignifies and maintains the desired shape (at which point the wire should be removed). Some species do not lignify strongly, or are already too stiff/brittle to be shaped and are not conducive to wiring, in which case shaping must be accomplished primarily through pruning.

To simulate age and maturity in a bonsai, techniques called Jin and Shari can be used. Jin is done by removing the bark in an area of a large branch or the trunk, while Shari is the stripping off of an entire branch. These techniques simulate scarring by nature and limbs being torn off. Care must be taken when employing these techniques, because these areas are prone to infection, and removal of too much bark will result in losing all growth above that area. Also bark must never be removed in a complete ring around the trunk as it will cut off all water and nutrient flow above that ring.

(Original Source : Wikipedia Encyclopedia, Other Photo Source : Google Images)