What is Defence against herbivory?
[[File:Toxicodendron radicans.jpg|thumb|[[Poison ivy]] produces [[urushiol]] to protect the plant from herbivores. In humans this chemical produces an allergic skin rash.]] [[File:Foxglove2.jpg|thumb|[[Foxglove]]s produce several deadly chemicals, namely heart and [[steroid]]al [[glycoside]]s. Eating it can cause [[nausea]], [[vomit]]ing, [[hallucination]]s, [[convulsion]]s, or [[death]].]] '''Defence against herbivory''' describes [[plant]] defences to avoid being eaten. There are many [[adaptation]]s which improve the [[fitness|survival and reproduction]] of plants by reducing the effect of [[herbivore]]s. Many plants produce [[chemical]]s which change the [[behaviour]], [[growth]], or survival of herbivores. These chemical defences can act as repellents or [[toxin]]s to herbivores, or reduce plant digestibility. Some plants, known as [[hyperaccumulators]], specialise in storing [[heavy metals]] which are toxic to animals. Some plants encourage the presence of [[predator|natural enemies]] of herbivores, which in turn protect the plant. Some plants provide a home for [[ants]] which defend the plant strongly. Other defensive strategies used by plants include escaping or avoiding herbivores in time or in place. They may grow where plants are not easily found or got at by herbivores. They may grow when herbivores are not around. Herbivores may get diverted towards non-essential parts, or a plant may be able to recover from the damage caused by herbivory. Each type of defence can be either ''constitutive'' (always present in the plant), or ''induced'' (produced in reaction to damage or stress caused by herbivores). Plants can and do react to damage.<ref>Boyd, Jade 2012. A bit touchy: Plants' insect defenses activated by touch. Rice University. [http://news.rice.edu/2012/04/09/a-bit-touchy-plants-insect-defenses-activated-by-touch-2/] {{Webarchive|url=https://web.archive.org/web/20120512012546/http://news.rice.edu/2012/04/09/a-bit-touchy-plants-insect-defenses-activated-by-touch-2/ |date=2012-05-12 }}</ref> His