Editing Vacuole (section)

=== Central ===
[[File:Rhoeo_Discolor_-_Plasmolysis.jpg|thumb|The [[anthocyanin]]-storing vacuoles of ''Rhoeo spathacea'', a [[spiderwort]], in cells that have plasmolyzed]]
Most mature [[plant cell]]s have one large vacuole that typically occupies more than 30% of the cell's volume, and that can occupy as much as 80% of the volume for certain cell types and conditions.<ref>{{cite book|url=https://archive.org/details/molecularbiology00albe_292|title=Molecular Biology of the Cell|vauthors=Alberts B, Johnson B, Lewis A, Raff J, Roberts K, Walter P|date=2008|publisher=Garland Science|isbn=978-0-8153-4111-6|edition=Fifth|location=New York|page=[https://archive.org/details/molecularbiology00albe_292/page/n814 781]|url-access=limited}}</ref> Strands of [[cytoplasm]] often run through the vacuole.

A vacuole is surrounded by a membrane called the '''tonoplast''' (word origin: Gk tón(os) + -o-, meaning “stretching”, “tension”, “tone” + comb. form repr. Gk plastós formed, molded) and filled with '''cell sap'''. Also called the '''vacuolar membrane''', the tonoplast is the cytoplasmic membrane surrounding a vacuole, separating the vacuolar contents from the cell's cytoplasm. As a membrane, it is mainly involved in regulating the movements of ions around the cell, and isolating materials that might be harmful or a threat to the cell.<ref>{{cite journal|vauthors=Li WY, Wong FL, Tsai SN, Phang TH, Shao G, Lam HM|date=June 2006|title=Tonoplast-located GmCLC1 and GmNHX1 from soybean enhance NaCl tolerance in transgenic bright yellow (BY)-2 cells|journal=Plant, Cell & Environment|volume=29|issue=6|pages=1122–37|doi=10.1111/j.1365-3040.2005.01487.x|pmid=17080938|doi-access=free}}</ref>

Transport of [[proton]]s from the cytosol to the vacuole stabilizes cytoplasmic [[pH]], while making the vacuolar interior more acidic creating a [[proton motive force]] which the cell can use to transport nutrients into or out of the vacuole. The low pH of the vacuole also allows [[degradative enzyme]]s to act. Although single large vacuoles are most common, the size and number of vacuoles may vary in different tissues and stages of development. For example, developing cells in the [[meristems]] contain small provacuoles and cells of the [[vascular cambium]] have many small vacuoles in the winter and one large one in the summer.

Aside from storage, the main role of the central vacuole is to maintain [[turgor]] pressure against the [[cell wall]]. Proteins found in the tonoplast ([[aquaporins]]) control the flow of water into and out of the vacuole through [[active transport]], pumping [[potassium]] (K<sup>+</sup>) [[ion]]s into and out of the vacuolar interior. Due to [[osmosis]], water will diffuse into the vacuole, placing pressure on the cell wall. If water loss leads to a significant decline in turgor pressure, the [[Cell (biology)|cell]] will [[Plasmolysis|plasmolyze]]. Turgor pressure exerted by vacuoles is also required for cellular elongation: as the cell wall is partially degraded by the action of [[expansin]]s, the less rigid wall is expanded by the pressure coming from within the vacuole. Turgor pressure exerted by the vacuole is also essential in supporting plants in an upright position. Another function of a central vacuole is that it pushes all contents of the cell's cytoplasm against the cellular membrane, and thus keeps the [[chloroplasts]] closer to light.<ref>{{cite book|last1=Taiz|first1=Lincoln|title=Plant Physiology|last2=Zeiger|first2=Eduardo|date=2002|publisher=Sinauer|isbn=0-87893-856-7|edition=3rd|pages=13–14|name-list-style=vanc}}</ref> Most plants store chemicals in the vacuole that react with chemicals in the cytosol. If the cell is broken, for example by a [[herbivore]], then the two chemicals can react forming toxic chemicals. In garlic, [[alliin]] and the enzyme [[alliinase]] are normally separated but form [[allicin]] if the vacuole is broken. A similar reaction is responsible for the production of [[syn-propanethial-S-oxide]] when [[onion]]s are cut.<ref name="Onion-Garlic-flavour-2010">{{cite web |last1=Jones |first1=Meriel G. |title=Knowing your Alliums |url=https://www.soci.org/chemistry-and-industry/cni-data/2010/10/knowing-your-alliums |website=Chemistry & Industry |access-date=30 April 2025}}</ref>

Vacuoles in fungal cells perform similar functions to those in plants and there can be more than one vacuole per cell. In [[Saccharomyces cerevisiae|yeast]] cells the vacuole ([[Vac7]]) is a [[wiktionary:dynamic|dynamic]] structure that can rapidly modify its [[Morphology (biology)|morphology]]. They are involved in many processes including the [[homeostasis]] of cell pH and the concentration of ions, [[osmoregulation]], storing [[amino acids]] and [[polyphosphate]] and degradative processes. Toxic ions, such as [[strontium]] ({{chem|Sr|2+}}), [[cobalt]](II) ({{chem|Co|2+}}), and [[lead]](II) ({{chem|Pb|2+}}) are transported into the vacuole to isolate them from the rest of the cell.<ref>{{cite journal|vauthors=Klionsky DJ, Herman PK, Emr SD|date=September 1990|title=The fungal vacuole: composition, function, and biogenesis|journal=Microbiological Reviews|volume=54|issue=3|pages=266–92|doi=10.1128/MMBR.54.3.266-292.1990|pmc=372777|pmid=2215422}}</ref>