Editing Plasmolysis

{{Short description|Process by which  cells lose water in a hypertonic solution}}
{{Infobox medical condition 
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 |image           = Blausen 0683 OsmoticFlow Hypertonic.png
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 |caption         = A red blood cell in a hypertonic solution, causing water to move out of the cell.
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 |specialty       = [[Cell biology]]
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 |causes          = [[Osmosis]]
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{{Multiple image|direction=vertical|align=right|image1=Rhoeo Discolor epidermis.jpg|image2=Rhoeo Discolor - Plasmolysis.jpg|width=180|caption2=Before plasmolysis (top) and after (bottom)}}
'''Plasmolysis''' is the process in which cells lose water in a [[hypertonic]] solution. The reverse process, [[deplasmolysation|deplasmolysis]] or [[cytolysis]], can occur if the cell is in a [[Tonicity#Hypotonicity|hypotonic]] solution resulting in a lower external [[osmotic pressure]] and a net flow of water into the cell. Through observation of plasmolysis and deplasmolysis, it is possible to determine the [[tonicity]] of the cell's environment as well as the rate solute molecules cross the [[Cell membrane|cellular membrane]].

==Etymology==
The term plasmolysis is derived from the Latin word ‘plasma’ meaning ‘matrix’ and the Greek word ‘lysis’, meaning ‘loosening’.

== Turgidity ==
{{main|Turgor pressure}}
A plant cell in hypotonic solution will absorb water by [[endosmosis]], so that the increased volume of water in the cell will increase pressure, making the [[protoplasm]] push against the [[cell wall]], a condition known as [[turgor]]. Turgor makes plant cells push against each other in the same way and is the main line method of support in non-woody plant tissue. Plant cell walls resist further water entry after a certain point, known as full turgor, which stops plant cells from bursting as animal cells do in the same conditions. This is also the reason that plants stand upright. Without the stiffness of the plant cells the plant would fall under its own weight.  Turgor pressure allows plants to stay firm and erect, and plants without turgor pressure (known as flaccid) wilt. A cell will begin to decline in turgor pressure only when there is no air spaces surrounding it and eventually leads to a greater osmotic pressure than that of the cell.<ref>{{Cite book|title=Plants in Action|last=Munns|first=Rana|publisher=Australian Society of Plant Scientists|year=2010}}</ref> Vacuoles play a role in turgor pressure when water leaves the cell due to [[hyperosmotic]] solutions containing solutes such as [[mannitol]], [[sorbitol]], and [[sucrose]].<ref name="[1]">{{cite journal|last1=Lang|first1=Ingeborg|last2=Sassmann|first2=Stefan|last3=Schmidt|first3=Brigitte|last4=Komis|first4=George|year=2014|title=Plasmolysis: Loss of Turgor and Beyond|journal=Plants|volume=3|issue=4|pages=583–93|doi=10.3390/plants3040583|pmc=4844282|pmid=27135521|doi-access=free|bibcode=2014Plnts...3..583L }}</ref>

[[File:Plasmolysed Plant Cell.jpg|thumb|right|Plant cell undergoing Plasmolysis in a Hypertonic solution (x400 magnification)]]

== Plasmolysis ==
[[Image:Turgor pressure on plant cells diagram.svg|thumb|300px|right|Plant cell under different environments]] If a plant cell is placed in a [[Tonicity#Hypertonic solution|hypertonic]] solution, the plant cell loses water and hence [[turgor]] pressure by plasmolysis: pressure decreases to the point where the protoplasm of the cell peels away from the cell wall, leaving gaps between the cell wall and the membrane and making the plant cell shrink and crumple.  A continued decrease in pressure eventually leads to [[cytorrhysis]] – the complete collapse of the cell wall. Plants with cells in this condition wilt. After plasmolysis the gap between the cell wall and the cell membrane in a plant cell is filled with [[hypertonic]] solution. This is because as the solution surrounding the cell is hypertonic, [[exosmosis]] takes place and the space between the cell wall and cytoplasm is filled with solutes, as most of the water drains away and hence the concentration inside the cell becomes more hypertonic. There are some mechanisms in plants to prevent excess water loss in the same way as excess water gain. Plasmolysis can be reversed if the cell is placed in a [[hypotonic]] solution. [[Stoma]]ta close to help keep water in the plant so it does not dry out. [[Wax]] also keeps water in the plant. The equivalent process in animal cells is called [[crenation]]. 
The liquid content of the cell leaks out due to exosmosis. The cell collapses, and the cell membrane pulls away from the cell wall (in plants). Most animal cells consist of only a [[Lipid bilayer|phospholipid bilayer]] ([[plasma membrane]]) and not a cell wall, therefore shrinking up under such conditions.

Plasmolysis only occurs in extreme conditions and rarely occurs in nature. It is induced in the laboratory by immersing cells in strong [[Saline (medicine)|saline]] or sugar (sucrose) solutions to cause [[exosmosis]], often using ''[[Elodea]]'' plants or [[onion epidermal cell]]s, which have colored cell sap so that the process is clearly visible.  [[Methylene blue]] can be used to stain plant cells.

Plasmolysis is mainly known as shrinking of cell membrane in hypertonic solution and great pressure.

Plasmolysis can be of two types, either concave plasmolysis or convex plasmolysis. Convex plasmolysis is always irreversible while concave plasmolysis is usually reversible.<ref name="[1]" /> During concave plasmolysis, the plasma membrane and the enclosed protoplast partially shrinks from the cell wall due to half-spherical, inwarding curving pockets forming between the plasma membrane and the cell wall. During convex plasmolysis, the plasma membrane and the enclosed protoplast shrinks completely from the cell wall, with the plasma membrane's ends in a symmetrically, spherically curved pattern.<ref name="[1]" />

==References==
{{Reflist}}

== External links ==

* Pictures of plasmolysis in [[Elodea]] and onion skin. {{webarchive |url=https://web.archive.org/web/20080416083006/http://www.pgjr.alpine.k12.ut.us/science/whitaker/Cell_Chemistry/Plasmolysis.html |date=April 16, 2008 }}
* Wilting and plasmolysis. {{webarchive |url=https://web.archive.org/web/20071014032730/http://4e.plantphys.net/article.php?ch=3&id=31 |date=October 14, 2007 }}

[[Category:Plant physiology]]
[[Category:Membrane biology]]