| 词条 | Plasmolysis |
| 释义 |
Plasmolysis is the process in which cells lose water in a hypertonic solution. The reverse process, cytolysis, can occur if the cell is in a 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 cellular membrane. 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.[1] Vacuoles play a role in turgor pressure when water leaves the cell due to hyperosmotic solutions containing solutes such as mannitol, sorbitol, and sucrose.[2] PlasmolysisThe 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 phospholipid bilayer (plasma membrane) and not a cell wall, therefore shrinking up under such conditions. Plasmolysis only occurs in extreme conditions and rarely happens in nature. It is induced in the laboratory by immersing cells in strong saline or sugar (sucrose) solutions to cause exosmosis, often using Elodea plants or onion epidermal cells, 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.[3] 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.[4] See also
References1. ^{{Cite book|title=Plants in Action|last=Munns|first=Rana|publisher=Australian Society of Plant Scientists|year=2010|isbn=|location=|pages=}} 2. ^{{Cite journal|last=Lang|first=Ingeborg|date=10 September 2014|title=Plasmolysis: Loss of Turgor and Beyond|url=http://www.mdpi.com/2223-7747/3/4/583/pdf|journal=Plants|doi=|pmid=|access-date=}} 3. ^{{Cite journal|last=Lang|first=Ingeborg|last2=Sassmann|first2=Stefan|last3=Schmidt|first3=Brigitte|last4=Komis|first4=George|date=2014-11-26|title=Plasmolysis: Loss of Turgor and Beyond|url=http://www.mdpi.com/2223-7747/3/4/583|journal=Plants|language=en|volume=3|issue=4|pages=583–593|doi=10.3390/plants3040583|pmc=4844282|pmid=27135521}} 4. ^{{cite web|last1=Lang|first1=Ingeborg|last2=Sassmann|first2=Stefan|last3=Schmidt|first3=Brigitte|last4=Komis|first4=George|title=Plasmolysis: Loss of Turgor and Beyond|url=http://www.mdpi.com/2223-7747/3/4/583/htm|website=Plants|accessdate=10 March 2016}} External links
2 : Plant physiology|Membrane biology |
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