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Fritz Haber was a German chemist whose conversion of atmospheric nitrogen to ammonia opened the way for the synthetic fertilizer industry. His study of the combustion of hydrocarbons led to the commercial cracking or fractional distillation of natural oil

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Introduction

Fritz Haber was a German chemist whose conversion of atmospheric nitrogen to ammonia opened the way for the synthetic fertilizer industry. His study of the combustion of hydrocarbons led to the commercial cracking or fractional distillation of natural oil (petroleum) into its components (for example, diesel, gasoline, and paraffin). In electrochemistry, he was the first to demonstrate that oxidation and reduction take place at the electrodes; from this he developed a general electrochemical theory. At the outbreak of war, the German Army asked the Institute to investigate substitutes for explosive in shells, and poison gas was suggested. Haber, after watching early trials with gas shells, proposed releasing gas from cylinders. He became one of the principals in the German chemical warfare effort, devising weapons and gas masks, leading to protests against his Nobel Prize 1918. Fritz Haber invented the process used all over the world to make ammonia from nitrogen and hydrogen. He also devised gases for the World War effort on Germany's behalf, such as chlorine, phosgene and mustard gas. He described the use of such gas as 'a higher form of killing.' im: The aim of this science investigation is to find out where the stomata are located, on the upper or lower epidermis of a leaf. ...read more.

Middle

The controlled opening and closing of the stomata resolve the conflicting needs of the plant. In order to appreciate how the stomata are controlled we must first understand the mechanism by which they open and close, and this necessitates looking at their structure. A pair of guard cells borders the stomata pore. These are sausage-shaped and, unlike other epidermal cells, contain chloroplasts. There is a sap vacuole and, a point of great importance; the inner cellulose wall (i.e. the wall lining the pore itself) is thicker and less elastic than the thinner outer wall. Stomata opening and closure depends on changes in turgor of the guard cells. If water is drawn into the guard cells by osmosis the cells expand and their turgidity is increased. But they do not expand uniformly in all directions. The thick, inelastic inner wall makes them bend. The result is that the inner walls of the two guard cells draw apart from each other and the pore opens. The same effect can be achieved by blowing up a sausage- shaped balloon to which cellotape has been stuck down one side. As it is blown up it will bend over towards the cellotaped side. ...read more.

Conclusion

In the morning the resumption of photosynthesis lowers the concentration of carbon dioxide. As a result the level of carbonic acid falls, the pH rises, starch is converted to sugar, the osmotic pressure of the guard cells increases, and the stoma opens. This theory leaves a number of facts unexplained. For example, starch is absent from the guard cells of certain plants; some guard cells lack chloroplasts but still open and close; and the stomata movements of some plants may not necessarily be related to the time of day; in fact in some plants they open at night and close by day. One possibility is that opening is achieved by ions being actively transported into the guard cells from neighboring epidermal cells, thereby building up the necessary solute concentration for drawing in water by osmosis. There is evidence that in tobacco leaves potassium ions can be actively pumped into guard cells. Alternatively water itself may be pumped into or out of the guard cells. When the stomata are open carbon dioxide diffuses into the sub-stomata air chambers and thence into the intercellular spaces between mesophyll cells. When it comes into contact with the wet surface of a cell it goes into solution and diffuses into the cytoplasm. The fixation of carbon dioxide in the dark reactions of photosynthesis creates a concentration gradient that carbon dioxide continues to diffuse into the leaf. Plan: ...read more.

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