tag:blogger.com,1999:blog-37148773.post8075058495256685404..comments2024-03-27T14:50:47.345-04:00Comments on <center>Sandwalk</center>: Nobel Laureate: Melvin CalvinLarry Moranhttp://www.blogger.com/profile/05756598746605455848noreply@blogger.comBlogger3125tag:blogger.com,1999:blog-37148773.post-84859871782483640832012-01-05T23:28:17.891-05:002012-01-05T23:28:17.891-05:00You took those words right out of my biology textb...You took those words right out of my biology textbook Prentice Hall "Biology" by Miller and Lavine.:-\Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-37148773.post-75347361361607846552009-09-23T14:03:58.245-04:002009-09-23T14:03:58.245-04:00a. Van Helmont’s Experiment: In the 1600’s, the Be...a. Van Helmont’s Experiment: In the 1600’s, the Belgian physician Jan Van Helmont devised an experiment to find out if plants grew by taking material out of the soil. Van Helmont determined the mass of a pot of a dry soil and a small seedling. Then, he planted the seedling in the pot of the soil. He watered it regularly. At the end of five years, the seedling, which by then had grown into a small tree, had gained about 75 kg. <br /><br />The mass of the soil, however, was almost unchanged. He concluded that most of the gain in mass had come from water, because that was the only thing he added.<br /><br />Van Helmont’s experiment accounts for the “hydrate”, or water, portion of the carbohydrate produced by photosynthesis. But where does the carbon of the “carbo-“ portion come from? Although Van Helmont did not realize it, carbon dioxide in the air made a major contribution to the mass of this tree. The carbon in the carbondioxide is used to make sugars and other carbohydrates in photosynthesis. Van Helmont had only part of the story, but he had made a major contribution to science.<br /><br />b. Priestley’s Experiment: More than 100 years after Van Helmont’s experiment, the English minister Joseph Priestley performed an experiment that would give another sight into the process of photosynthesis. Priestley took a candle, placed a glass jar over it, and watched as the flame gradually died out. Something in the air, Priestley reasoned, was necessary to keep a candle flame burning. When that substance was used up, the candle went out. That substance was oxygen.<br /><br />Priestley then found that if he placed a live sprig of mint under the jar and allowed a few days to pass, the candle could be relighted and would remain lighted for a while. The mint plant had produced the substance required for burning. In other words, it released oxygen.<br /><br />c. Jan Ingenhousz (late 1700s): Later, the Dutch scientist Jan Ingenhousz showed that the effect observed by Priestley occured only when the plant was exposed to light. The results of both Priwstley’s and Ingenhousz’s experiments showed that light is necessary for plants to produce oxygen.<br /><br />The experiments performed by Van Helmont, Priestley and Jan Ingenhousz led to work by other scientists who finally discovered that in the presence of light, plants transform carbon dioxide and water into carbohydrates, and they also release oxygen.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-37148773.post-14558874300811124572009-01-24T07:33:00.000-05:002009-01-24T07:33:00.000-05:00Larry, Got any good anecdotes about early thoughts...Larry, <BR/><BR/>Got any good anecdotes about early thoughts on photosynthesis? E.g., when did people begin to be curious about _how_ photosynthesis actually worked? 1700s??Anonymousnoreply@blogger.com