Editing Physiological plant disorder

[[File:Diseased Vine Leaf @ Paarl, South Africa.jpg|thumbnail|Deficit of micronutrients, vine.]]

'''[[Physiological]] plant disorders''' are caused by non-[[pathological]] conditions such as poor light, adverse weather, water-logging, [[Phytotoxicity|phytotoxic compounds]] or a lack of nutrients, and affect the functioning of the [[plant]] system. Physiological disorders are distinguished from [[plant disease]]s caused by [[pathogen]]s, such as a [[virus]] or [[fungus]].<ref name=Schutzki2007>{{cite web |last1=Schutzki |first1=R.E. |last2=Cregg |first2=B. |title=Abiotic plant disorders: Symptoms, signs and solutions. A diagnostic guide to problem solving |url=http://www.hrt.msu.edu/assets/PagePDFs/bert-cregg/schutski-and-cregg-abiotic.pdf |website=Michigan State University Department of Horticulture |publisher=Michigan State University |accessdate=10 April 2015 |date=2007 |url-status=dead |archiveurl=https://web.archive.org/web/20150924031539/http://www.hrt.msu.edu/assets/PagePDFs/bert-cregg/schutski-and-cregg-abiotic.pdf |archivedate=24 September 2015 }}</ref> While the symptoms of physiological disorders may appear disease-like, they can usually be prevented by altering environmental conditions. However, once a plant shows symptoms of a physiological disorder, it is likely that that season's growth or yield will be reduced.

==Diagnosis of disorders==
Diagnosis of the cause of a physiological disorder (or disease) can be difficult, but there are many web-based guides that may assist with this. Examples are: ''Abiotic plant disorders: Symptoms, signs and solutions'';<ref name=Schutzki2007 /> ''Georgia Corn Diagnostic Guide'';<ref name=Lee2012>{{cite web|last1=Lee|first1=R.D.|title=Georgia Corn Diagnostic Guide|url=http://extension.uga.edu/publications/detail.cfm?number=B1221|website=extension.uga.edu|publisher=University of Georgia Cooperative Extension|accessdate=10 April 2015|date=2012}}</ref> ''Diagnosing Plant Problems'' (Kentucky);<ref>{{cite web|last1=Green|first1=J.L.|last2=Maloy|first2=O.|last3=Capizzi|first3=J.|last4=Hartman|first4=J.|last5=Townsend|first5=L.|title=Diagnosing Plant Problems: Kentucky Master Gardener Manual Chapter 7|url=http://www2.ca.uky.edu/agc/pubs/id/id194/id194.pdf|website=www2.ca.uky.edu|publisher=Kentucky Cooperative Extension|accessdate=10 April 2015|date=2011}}</ref> and ''Diagnosing Plant Problems'' (Virginia).<ref>{{cite web|last1=Niemiera|first1=A.X.|title=Diagnosing Plant Problems|url=http://pubs.ext.vt.edu/426/426-714/426-714.html|website=pubs.ext.vt.edu|publisher=Virginia Cooperative Extension|accessdate=10 April 2015|date=2009}}</ref>

[[File:Apple sunburn1.jpg|thumbnail|Sunburn on apple.]]
Some general tips to diagnosing plant disorders:
*Examine where symptoms first appear on a plant—on new [[leaves]], old leaves or all over?
*Note the pattern of any discolouration or yellowing—is it all over, between the [[vein]]s or around the edges? If only the veins are yellow, deficiency is probably not involved.
*Note general patterns rather than looking at individual plants—are the symptoms distributed throughout a group of plants of the same type growing together? In the case of a deficiency all of the plants should be similarly effected, although distribution will depend on past treatments applied to the soil.
*Soil analysis, such as determining [[Soil pH|pH]], can help to confirm the presence of physiological disorders. 
*Considering recent conditions, such as heavy rains, dry spells, frosts, etc., may also help to determine the cause of plant disorders.

==Weather damage==
{{More citations needed|date=September 2024}}[[File:20120607 škola 3802u.JPG|thumbnail|Drought.]]
[[Frost]] and cold are major causes of [[crop]] damage to tender plants, although hardy plants can also suffer if new growth is exposed to a hard frost following a period of warm weather.<ref>{{Cite web |last1=Pennisi |first1=Bodie |last2=Thomas |first2=Paul |last3=Stallknect |first3=Eric |date=December 2016 |title=Effects of Low Temperature on Plants |url=https://extension.uga.edu/content/dam/extension-county-offices/catoosa-county/anr/Effects%20of%20Low%20Temperature%20on%20Plants.PDF |website=University of Georgia |series=Bulletin 1467 |pages=1–4 }}</ref> Symptoms will often appear overnight, affecting many types of plants. Leaves and stems may turn black, and buds and flowers may be discoloured, and frosted blooms may not produce [[fruit]]. Many [[Annual plant|annual]] plants, or plants grown in frost free areas, can suffer from damage when the air temperature drops below 40 degrees [[Fahrenheit]] (4 degrees [[Celsius]]). Tropical plants may begin to experience cold damage when the temperature is {{convert|42|to|48|F|C}}, symptoms include [[wilting]] of the top of the stems and/or leaves, and blackening or softening of the plant tissue.

Frost or cold damage can be avoided by ensuring that tender plants are properly [[Cold hardening|hardened]] before planting, and that they are not planted too early in the season, before the risk of frost has passed. Avoid planting susceptible plants in frost pockets, or where they will receive early morning sun. Protect young buds and bloom with [[horticultural fleece]] if frost is forecast. Cold, drying easterly winds can also severely inhibit spring growth even without an actual frost, thus adequate shelter or the use of windbreaks is important.

Drought can cause plants to suffer from water stress and wilt. Adequate [[irrigation]] is required during prolonged hot, dry periods. Rather than shallow daily watering, during a drought water should be directed towards the roots, ensuring that the soil is thoroughly soaked two or three times a week. [[Mulch]]es also help preserve soil moisture and keep roots cool.

Heavy rains, particularly after prolonged dry periods, can also cause roots to split, [[onion]] saddleback (splitting at the base), [[tomato]]es split and [[potato]]es to become deformed or hollow. Using mulches or adding organic matter such as [[leaf mold]], [[compost]] or well rotted [[manure]] to the [[soil]] will help to act as a 'buffer' between sudden changes in
conditions. Water-logging can occur on poorly drained soils, particularly following heavy rains. Plants can become yellow and stunted, and will tend to be more prone to drought and diseases. Improving drainage will help to alleviate this problem.

Hail can cause damage to soft skinned fruits, and may also allow [[Monilinia fructicola|brown rot]] or other [[fungi]] to penetrate the plant. Brown spot markings or lines on one side of a mature [[apple (fruit)|apple]] are indicative of a spring hailstorm.

Plants affected by [[salt]] stress are able to take water from soil, due to an [[osmotic]] imbalance between soil and plant.

==Nutrient deficiencies==
[[File:20120817 9999 103u.JPG|thumbnail|Iron deficiency.]]
Poor growth and a variety of disorders such as leaf discolouration ([[chlorosis]]) can be caused by a shortage of one or more plant nutrients. Poor plant uptake of a nutrient from the soil (or other growing medium) may be due to an absolute shortage of that element in the growing medium, or because that element is present in a form that is not available to the plant.<ref name=Mengel2001>{{cite book|last1=Mengel|first1=K.|last2=Kirkby|first2=E.A.|title=Principles of plant nutrition|date=2001|publisher=Kluwer Academic Publishers|location=Dordrecht|isbn=079237150X|edition=5th}}</ref> The latter can be caused by incorrect [[Soil pH|pH]], shortage of water, poor root growth or an excess of another nutrient.<ref name=Mengel2001 /> Plant nutrient deficiencies can be avoided or corrected using a variety of approaches including the consultation of experts on-site, the use of [[Soil test|soil]] and [[Plant tissue test|plant-tissue]] testing services, the application of prescription-blend [[fertilizer]]s, the application of fresh or well-decomposed [[Organic fertilizer|organic matter]], and the use of biological systems such as [[cover crop]]s, [[intercropping]], [[Crop rotation|improved fallows]],<ref>{{cite web|title=Improved fallows|url=http://teca.fao.org/read/7769|website=teca.fao.org|publisher=FAO|accessdate=10 April 2015|quote=Improved fallow is also land resting from cultivation but the vegetation comprises planted and managed species of leguminous trees, shrubs and herbaceous cover crops. These cover crops rapidly replenish soil fertility in one or at most two growing seasons. They shorten the time required to restore soil fertility; they help to improve farmland productivity because the plant vegetation that follows them is superior in quality; and they increase the range of outputs, because the woody fallow species can also produce fuel wood and stakes.|archive-url=https://web.archive.org/web/20171113160657/http://teca.fao.org/read/7769|archive-date=13 November 2017|url-status=dead}}</ref> [[Ley farming|ley]] cropping, [[permaculture]], or [[crop rotation]].

Nutrient (or mineral) deficiencies include:
*[[Boron deficiency (plant disorder)|Boron deficiency]]
*[[Calcium deficiency (plant disorder)|Calcium deficiency]]
*[[Iron deficiency (plant disorder)|Iron deficiency]]
*[[Magnesium deficiency (plants)|Magnesium deficiency]]
*[[Manganese deficiency (plant)|Manganese deficiency]]
*[[Molybdenum deficiency (plant disorder)|Molybdenum deficiency]]
*[[Nitrogen deficiency]]
*[[Phosphorus deficiency]]
*[[Potassium deficiency (plants)|Potassium deficiency]]
*[[Zinc deficiency (plant disorder)|Zinc deficiency]]

==References==
{{Reflist|33em}}

{{Plant disorders}}
{{Plant nutrition}}
{{physiology types}}

[[Category:Physiological plant disorders| 01]]
[[Category:Horticulture]]