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Push/pull Theory - Papers

Push/pull Theory


Plants need much more water to survive than animals do, a sunflower must take in 17 times more water than a human of comparable weight. At least 500 pounds of water must be lifted from the roots to the leaves to make a single pound of organic tissue. This tremendous amount of water is required to undergo photosynthesis each and every day of a plant's life. But how does a tree lift hundreds of gallons of water hundreds of feet in the air against the force of gravity? Scientists have developed two theories to explain this "impossible" phenomenon. In the following, I will discuss the theories and show how the pull theory is more viable.
The push theory states that positive pressure pushes up ...

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when soil is almost completely saturated with water and leaves are not losing much water through evaporation. When the xylem is full of water, the molecules will not move back down the structure, but rather need to be expelled from the plant. They will move, by the process of osmosis, to an areas where there is the least amount of pressure. These areas are usually openings located on plant leaves. Once the water molecules reach the leaves, the excess water will be forced out of the plant by root pressure.
This push theory presents two major inconsistencies 1)many plants exhibit no root pressure and 2)root pressure is not strong enough. In many plants and trees, there is a substantial amount of root pressure that could possibly explain the movement of so much water throughout a tree, defying gravity. However, in many plants, root pressure is not nearly enough to exert the amount of force needed to circulate such large quantities of water throughout the plant and against gravity. ...

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Push/pull Theory. (2006, August 11). Retrieved December 23, 2024, from http://www.essayworld.com/essays/Push-pull-Theory/50550
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"Push/pull Theory." Essayworld.com. August 11, 2006. Accessed December 23, 2024. http://www.essayworld.com/essays/Push-pull-Theory/50550.
"Push/pull Theory." Essayworld.com. August 11, 2006. Accessed December 23, 2024. http://www.essayworld.com/essays/Push-pull-Theory/50550.
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PAPER DETAILS
Added: 8/11/2006 02:37:59 AM
Category: Science & Nature
Type: Premium Paper
Words: 906
Pages: 4

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