User:Nr03casp/sandbox

Cavitation:
To maintain the pressure gradient necessary for a plant to remain healthy they must continuous uptake of water with their roots. They need to be able to meet the demands of water lost due to transpiration. If a plant is incapable of bringing in enough water to remain in equilibrium with transpiration an event known as cavitation occurs. Cavitation is when the plant cannot supply its xylem with adequate water so instead of being filled with water the xylem begins to be filled with water vapor. These particles of water vapor come together and form blockages within the xylem of the plant. This prevents the plant from being able to transport water throughout its vascular system. There is no apparent pattern of where cavitation occurs throughout the plant's xylem. If not effectively taken care of, cavitation can cause a plant to reach its permanent wilting point, and die. Therefore, the plant must have a method, by which to remove this cavitation blockage, or create a new connection of vascular tissue throughout the plant. The plant does this by, closing its stomates overnight which halts the flow of transpiration. This then allows for the roots to generate over 0.05 mPa of pressure which is capable of destroying the blockage and refilling the xylem with water, reconnecting the vascular system. If a plant is unable to generate enough pressure to eradicate the blockage it must prevent the blockage from spreading with the use of pit pears and then create new xylem that can re-connect the vascular system of the plant.

Scientists have begun using Magnetic Resonance Imaging (MRI) to monitor the the internal status of the xylem during transpiration, in a non invasive manor. This method of imaging allows for scientist to visualize the movement of water throughout the entirety of the plant. It also is capable of viewing what phase the water is in while in the xylem, which makes it possible to visualize cavitation events. Scientist were able to see that over the course of 20 hours of sunlight more than 10 xylem vessels began filling with gas particles becoming cavitated. MRI technology also made is possible to view the process by which the plant was able to repair these xylem structures. After 3 hours in darkness is was seen that the plant was able to resupply its vascular tissue with liquid water. This was possible because in darkness the stomates of the plant are closed and transpiration no longer occurs. When transpiration is halted the plant can destroy the cavitation bubbles with the use of pressure generated by the roots. These observations suggest that MRI's are capable of monitoring the functional status of xylem and allows scientist to view cavitation event for the first time.