1.6. ROOT PRESSURE AND SUCTION PRESSURE
The two main factors that cause water to move up the xylem vessel are root pressure and suction pressure. (transport pull). Root pressure is a force that builds up in the root to false water up the xylem vessels to a certain height. After this height another force called suction pressure which is created by constant transpiration pull the water through the xylem vessels to the leaf.
Suction pressure is due to the fact that the cell of the spongy mesophyll loose water by evaporation through the stomata into the atmosphere. The osmotic pressure of the spongy mesophyll increases because they have lost water into the atmosphere and so more water is drawn up from the surrounding cell and finally from xylem vessels.
1.6.1. EXPERIMENT TO DEMONSTRATE THAT PLANTS EXERT SUCTION PRESSURE.
Aim:
Experiment to demonstrate that plants exerts suction pressure.
Requirements:
A glass tube, a mercury beaker, a rubber band, a freshly cut stem, retort stand and clamp.
Procedure:
A glass tube is places in a beaker of mercury and the glass tube is connected by means of rubber band to a freshly cut shoot. The experiment is held in place by the means of clamp and retort stand
Results:
After a few hours the mercury rise into a glass tube because of force which is sucking it up.
Explanation:
When the leaf of the attached shoot transpired water is sucked up the xylem by a force which in urns suck up the mercury in the tube
Conclusion:
This shows that plants exert suction pressure.
The movement of water from the soil to the leave is controlled by 3 main process. (osmosis, root pressure, suction pressure). Osmosis and diffusion are responsible for the distribution of the neighboring cell of the different organ of the plant.
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Chubby kidz
November 17, 2020
Very interesting