Editing Frost (section)

===Damage===
[[File:Feuilles-avec-glace-leaves-with-ice-1.jpg|right|thumb|Frost on the grass of a public park in November]]
[[File:Geography of Ohio - DPLA - aaba7b3295ff6973b6fd1e23e33cde14 (page 31) (cropped).jpg|thumb|right|Map of average first killing frost in Ohio from "Geography of Ohio," 1923]]
Many plants can be damaged or killed by freezing temperatures or frost. This varies with the type of plant, the tissue exposed, and how low temperatures get; a "light frost" of {{convert|-2|to|0|C|F}} damages fewer types of plants than a "hard frost" below {{convert|-2|C|F}}.<ref name="BI_Frost">{{cite web |url=http://www.botanicalinterests.com/articles/view/26/Frost-Tolerance-of-Vegetables |title=Frost Tolerance of Vegetables |publisher=Botanical Interests |access-date=Nov 12, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20131113010216/http://www.botanicalinterests.com/articles/view/26/Frost-Tolerance-of-Vegetables |archive-date=2013-11-13 }}</ref><ref>{{Cite journal |last1=Beerling |first1=D. J. |last2=Terry |first2=A. C. |last3=Mitchell |first3=P. L. |last4=Callaghan |first4=T. V. |last5=Gwynn-Jones |first5=D. |last6=Lee |first6=J. A. |date=April 2001 |title=Time to chill: effects of simulated global change on leaf ice nucleation temperatures of subarctic vegetation |url=http://doi.wiley.com/10.2307/2657062 |journal=American Journal of Botany |language=en |volume=88 |issue=4 |pages=628–633 |doi=10.2307/2657062|jstor=2657062 |pmid=11302848 }}</ref>

Plants likely to be damaged even by a light frost include vines—such as beans, grapes, squashes, melons—along with [[nightshade]]s such as tomatoes, eggplants, and peppers. Plants that may tolerate (or even benefit from) frosts include:<ref>{{cite web |url=http://www.grow-it-organically.com/fall-vegetables.html |title=Fall vegetables vs. Summer vegetables |url-status=live |archive-url=https://web.archive.org/web/20131113011159/http://www.grow-it-organically.com/fall-vegetables.html |archive-date=2013-11-13 }}</ref>
*root vegetables (e.g. beets, carrots, parsnips, onions)
*leafy greens (e.g. lettuces, spinach, chard, cucumber<ref name="JHR_2-2013">{{Citation|last=Klosinska|first=Urszula|date=27 February 2014|publisher=de Gruyter|title=Low temperature seed germination of cucumber: genetic basis of the tolerance trait|journal=Journal of Horticultural Research|volume=21|issue=2|pages=125–130|display-authors=etal|doi=10.2478/johr-2013-0031|doi-access=free}}</ref>)
*[[cruciferous vegetables]] (e.g. cabbages, cauliflower, bok choy, broccoli, Brussels sprouts, radishes, kale, collard, mustard, turnips, rutabagas)
Even those plants that tolerate frost may be damaged once temperatures drop even lower (below {{convert|-4|C|F|disp=or}}).<ref name="BI_Frost"/> Hardy perennials, such as ''[[Hosta]]'', become dormant after the first frosts and regrow when spring arrives. The entire visible plant may turn completely brown until the spring warmth, or may drop all of its leaves and flowers, leaving the stem and stalk only. Evergreen plants, such as pine trees, withstand frost although all or most growth stops. [[Frost crack]] is a bark defect caused by a combination of low temperatures and heat from the winter sun.

Vegetation is not necessarily damaged when leaf temperatures drop below the freezing point of their cell contents. In the absence of a site [[nucleation|nucleating]] the formation of ice crystals, the leaves remain in a [[supercooled]] liquid state, safely reaching temperatures of {{convert|-4|to|-12|C|F}}. However, once frost forms, the leaf [[cell (biology)|cells]] may be damaged by sharp ice crystals. [[Hardening (botany)|Hardening]] is the process by which a plant becomes tolerant to low temperatures. See also [[Cryobiology]].

Certain [[bacterium|bacteria]], notably ''[[Pseudomonas syringae]]'', are particularly effective at triggering frost formation, raising the nucleation temperature to about {{convert|-2|C|F}}.<ref>{{cite journal |vauthors=Maki LR, Galyan EL, Chang-Chien MM, Caldwell DR |title=Ice Nucleation Induced by Pseudomonas syringae |journal=Applied Microbiology |volume=28 |issue=3 |year=1974 |pages=456–459 |pmid=4371331 |pmc=186742 |doi=10.1128/aem.28.3.456-459.1974}}</ref> Bacteria lacking ice nucleation-active proteins ([[ice-minus bacteria]]) result in greatly reduced frost damage.<ref>{{cite journal
|last= Lindow |first= Stephen E. |author-link= Steven E. Lindow |author2=Deane C. Arny |author3=Christen D. Upper |title= Bacterial Ice Nucleation: A Factor in Frost Injury to Plants
|journal= Plant Physiology
|volume= 70
|issue= 4
|pages= 1084–1089
|date= October 1982
|pmid= 16662618
|doi= 10.1104/pp.70.4.1084
|pmc= 1065830}}</ref>