Injuries can be caused in many ways, including mechanically withpenetration by sharp objects such asteeth orwith blunt objects, by heat or cold, or byvenoms andbiotoxins. Injury prompts aninflammatory response in manytaxa of animals; this promptswound healing. In both plants and animals, substances are often released to help to occlude the wound, limiting loss of fluids and the entry ofpathogens such as bacteria. Many organisms secreteantimicrobial chemicals which limit wound infection; in addition, animals have a variety ofimmune responses for the same purpose. Both plants and animals have regrowth mechanisms which may result in complete or partial healing over the injury. Cells too canrepair damage to a certain degree.
Injury in animals is sometimes defined as mechanical damage to anatomical structure,[1] but it has a wider connotation of physical damage with any cause, includingdrowning,burns, andpoisoning.[2] Such damage may result from attemptedpredation, territorial fights, falls, and abiotic factors.[2]
In plants, injuries result from the eating of plant parts byherbivorous animals including insects andmammals,[10] from damage to tissues byplant pathogens such as bacteria andfungi, which may gain entry after herbivore damage or in other ways,[11] and from abiotic factors such as heat,[12] freezing,[13] flooding,[14] lightning,[15] and pollutants[16] such as ozone.[17] Plants respond to injury by signalling that damage has occurred,[18] by secreting materials to seal off the damaged area,[19] by producingantimicrobial chemicals,[20][21] and in woody plants by regrowing over wounds.[22][23][24]
Cell injury is a variety of changes of stress that acell suffers due to external as well as internal environmental changes. Amongst other causes, this can be due to physical, chemical, infectious, biological, nutritional or immunological factors. Cell damage can be reversible or irreversible. Depending on the extent of injury, the cellular response may be adaptive and where possible,homeostasis is restored.[25] Cell death occurs when the severity of the injury exceeds the cell's ability to repair itself.[26] Cell death is relative to both the length of exposure to a harmful stimulus and the severity of the damage caused.[25]
^Smillie, R.M.; Nott, R. (1979). "Heat Injury in Leaves of Alpine, Temperate and Tropical Plants".Functional Plant Biology.6 (1). CSIRO Publishing: 135.doi:10.1071/pp9790135.ISSN1445-4408.
^Burke, M. J.; Gusta, L. V.; Quamme, H. A.; Weiser, C. J.; Li, P. H. (1976). "Freezing and Injury in Plants".Annual Review of Plant Physiology.27 (1). Annual Reviews:507–528.doi:10.1146/annurev.pp.27.060176.002451.ISSN0066-4294.
^Sun, Qiang; Rost, Thomas L.; Matthews, Mark A. (2008). "Wound-induced vascular occlusions inVitis vinifera (Vitaceae): Tyloses in summer and gels in winter1".American Journal of Botany.95 (12). Wiley:1498–1505.doi:10.3732/ajb.0800061.ISSN0002-9122.PMID21628157.
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