Bio notes. - In a real plant where would water come from...

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a real plant where would water come from? Hugo asked. Guard cells bordered by accessory cells. So von mol proposed the differential photosynthetic hypothesis. In the light the guard cells photosize at a higher rate than the acc. Cells so sugar increase in guard cells so lower conc. Of water and then would diffuse in from acc. Cells causing stoma to open. In nighttime the rate of metabolism is greater in guard cells so reverse happens and close We can predict/expect three things he did 1. we would expect to see the stoma open in the light 2. the rate of photosynthesis must be greater in the guard cells than in the accessory cells so there is an osmotic differential These weren’t tested until 1950s thought with the invention of the atomic bomb, came all new technology. So we could make minute measurements due to isotopes……bathe stoma in carbon14 co2 then measure the rate that it is taken up as sugar. And confirmed mol’s second prediction, however only 1/50 or 2% of what was required. So hypothesis fails. F. e. Lloyd. Proposed that there is an enzymatic conversion form starch into glucose so when time to open stoma, guard cells convert starch into glucose. The water concentration drops and water moves from acceso. Cells to guard cells to increase water in g. cells. At night opposite happens. Found when stoma were closed the starch conc. Were high and when closed sug. Was high and starch conc. Was low JD sayer extends hypothesis by saying switch of starch/ glucose is pH dependent. Lloyd sayer hypothesis got ground when enzyme phosphorylase was discovered which converts starch to glucose. When carbonic acid goes down bc carbon dissolved in water., ph goes up, phosphorylase turns starch into glucose Two problems…. . 1. no phosphorus in starch so need 100 phosphates. So no net in change in osmotic pressure b/c now have 101 molec. To 100 molec. 2. open/close reaction requ. Energy so need ATP. The walls of the guard cells and acc. Cells have lots of protein pumps that use active transport can pump potassium in either direction. So when time to open stoma potassium is rapidly into guard cells and water follows and then opposite happens when stoma close. Its inablility to find something wrong with hypo. That leads us to belive that it is true. C4 plants are much more abundant in low water plants. (sagebrush area, cliffs, icy environments. and deserts) Photosynthesis. End product of rubisco is glyceraldehyde phosphate which is turned into sugar…. . Example where biochem and physiology are coupled. Reliant on each other. Why are so many things in biochemm arranged in cycles….so they don’t stop. This system forms a sink (drain) product of big reaction is drained away from place where it takes place. Mass transport equation is in written notes.
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This note was uploaded on 01/05/2012 for the course BIOL 102 taught by Professor Reeves during the Spring '08 term at South Carolina.

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Bio notes. - In a real plant where would water come from...

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