Physiological plant disorders
Encyclopedia
Physiological plant disorders are caused by non-pathological disorders such as poor light, weather damage, water-logging or a lack of nutrients, and affect the functioning of the plant
system. Physiological disorder are distinguished from plant diseases caused by pathogen
s, such as a virus
or fungus
. Whilst 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 nutrient deficiency it is likely that that season’s yields will be reduced.
Causes of physiological disorders can be identified by examining:
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. 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
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 42 to 48 °F (5 to 9 °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 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 brown rot
or other fungi to penetrate the plant. Brown spot markings or lines on one side of a mature apple are indicative of a spring hailstorm.
Plants affected by salt
stress are unable to take water from soil, due to an osmotic imbalance between soil and plant.
, shortages of water or an excess of another nutrient. Generally, the key to avoiding nutrient deficiencies is to ensure that the soil is healthy and contains plenty of well rotted organic matter rather than by feeding or treating individual plants.
Nutrient (or mineral) deficiencies include:
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
system. Physiological disorder are distinguished from plant diseases caused by pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...
s, such as a virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
or fungus
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
. Whilst 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 nutrient deficiency it is likely that that season’s yields will be reduced.
Causes of physiological disorders can be identified by examining:
- Where symptoms first appear on a plant—on new leavesLeaves-History:Vocalist Arnar Gudjonsson was formerly the guitarist with Mower, and he was joined by Hallur Hallsson , Arnar Ólafsson , Bjarni Grímsson , and Andri Ásgrímsson . Late in 2001 they played with Emiliana Torrini and drew early praise from the New York Times...
, old leaves or all over? - The pattern of any discolouration or yellowing—is it all over, between the veinVeinIn the circulatory system, veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart...
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 pHSoil pHThe soil pH is a measure of the acidity or basicity in soils. pH is defined as the negative logarithm of the activity of hydrogen ions in solution. It ranges from 0 to 14, with 7 being neutral. A pH below 7 is acidic and above 7 is basic. Soil pH is considered a master variable in soils as it...
, can help to confirm the presence of physiological disorders. Recent conditions, such as heavy rains, dry spells, frosts, etc., may also help to determine the cause of plant disorders.
Weather damage
Frost
Frost is the solid deposition of water vapor from saturated air. It is formed when solid surfaces are cooled to below the dew point of the adjacent air as well as below the freezing point of water. Frost crystals' size differ depending on time and water vapour available. Frost is also usually...
and cold are major causes of crop
Crop
Crop may refer to:* Crop, a plant grown and harvested for agricultural use* Crop , part of the alimentary tract of some animals* Crop , a modified whip used in horseback riding or disciplining humans...
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. 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
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
. Many annual
Annual plant
An annual plant is a plant that usually germinates, flowers, and dies in a year or season. True annuals will only live longer than a year if they are prevented from setting seed...
plants, or plants grown in frost free areas, can suffer from damage when the air temperature drops below 40 degrees Fahrenheit
Fahrenheit
Fahrenheit is the temperature scale proposed in 1724 by, and named after, the German physicist Daniel Gabriel Fahrenheit . Within this scale, the freezing of water into ice is defined at 32 degrees, while the boiling point of water is defined to be 212 degrees...
(4 degrees Celsius
Celsius
Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
). Tropical plants may begin to experience cold damage when the temperature is 42 to 48 °F (5 to 9 °C), symptoms include wilting
Wilting
Wilting refers to the loss of rigidity of non-woody parts of plants. This occurs when the turgor pressure in non-lignified plant cells falls towards zero, as a result of diminished water in the cells...
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 hardened
Cold hardening
Cold hardening is the physiological and biochemical process by which an organism prepares for cold weather.-Plants:During the winter months, as the leaves fall off deciduous species and the temperature drops, the cold forces a stop to water movement in plants. Freezing water can also cause...
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
Horticultural fleece
Horticultural fleece is a thin, unwoven, polypropylene fabric that is used as a floating mulch to protect early crops and other delicate plants from cold weather, frost, and insect pests...
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
Irrigation
Irrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall...
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
Mulch
In agriculture and gardening, is a protective cover placed over the soil to retain moisture, reduce erosion, provide nutrients, and suppress weed growth and seed germination. Mulching in gardens and landscaping mimics the leaf cover that is found on forest floors....
es also help preserve soil moisture and keep roots cool.
Heavy rains, particularly after prolonged dry periods, can also cause roots to split, onion
Onion
The onion , also known as the bulb onion, common onion and garden onion, is the most widely cultivated species of the genus Allium. The genus Allium also contains a number of other species variously referred to as onions and cultivated for food, such as the Japanese bunching onion The onion...
saddleback (splitting at the base), tomato
Tomato
The word "tomato" may refer to the plant or the edible, typically red, fruit which it bears. Originating in South America, the tomato was spread around the world following the Spanish colonization of the Americas, and its many varieties are now widely grown, often in greenhouses in cooler...
es split and potato
Potato
The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species...
es to become deformed or hollow. Using mulches or adding organic matter such as leaf mold
Leaf mold
Leaf mold is a form of compost produced by the fungal breakdown of shrub and tree leaves, which are generally too dry, acidic, or low in nitrogen for bacterial decomposition.-Description:...
, compost
Compost
Compost is organic matter that has been decomposed and recycled as a fertilizer and soil amendment. Compost is a key ingredient in organic farming. At its most essential, the process of composting requires simply piling up waste outdoors and waiting for the materials to break down from anywhere...
or well rotted manure
Manure
Manure is organic matter used as organic fertilizer in agriculture. Manures contribute to the fertility of the soil by adding organic matter and nutrients, such as nitrogen, that are trapped by bacteria in the soil...
to the soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
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 brown rot
Brown rot
Brown rot may refer to the following diseases:*Wood-decay fungus, a disease of trees and wood.*Ralstonia solanacearum, a disease of plants caused by bacteria.*Monilinia fructicola, a disease of stone fruits....
or other fungi to penetrate the plant. Brown spot markings or lines on one side of a mature apple are indicative of a spring hailstorm.
Plants affected by salt
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...
stress are unable to take water from soil, due to an osmotic imbalance between soil and plant.
Nutrient deficiencies
Poor growth and a variety of complaints such as leaf discolouration (chlorosis) can be caused by a lack of plant foods. This may be due to shortages of necessary nutrients, or because the nutrients are present but not available to the plant. The latter can be caused by incorrect pHSoil pH
The soil pH is a measure of the acidity or basicity in soils. pH is defined as the negative logarithm of the activity of hydrogen ions in solution. It ranges from 0 to 14, with 7 being neutral. A pH below 7 is acidic and above 7 is basic. Soil pH is considered a master variable in soils as it...
, shortages of water or an excess of another nutrient. Generally, the key to avoiding nutrient deficiencies is to ensure that the soil is healthy and contains plenty of well rotted organic matter rather than by feeding or treating individual plants.
Nutrient (or mineral) deficiencies include:
- Boron deficiencyBoron deficiency (plant disorder)Boron deficiency is an uncommon disorder affecting plants growing in deficient soils and is often associated with areas of high rainfall and leached soils. Boron may be present but locked up in soils with a high pH, and the deficiency may be worse in wet seasons. Most of what is known about boron...
- Calcium deficiencyCalcium deficiency (plant disorder)Calcium deficiency is a plant disorder that can be caused by insufficient calcium in the growing medium, but is more frequently a product of low transpiration of the whole plant or more commonly the affected tissue. Plants are susceptible to such localized calcium deficiencies in low or non...
- Iron deficiencyIron deficiency (plant disorder)Iron deficiency is a plant disorder also known as "lime-induced chlorosis". It can be confused with manganese deficiency. A deficiency in the soil is rare but iron can be unavailable for absorption if soil pH is not between about 5 and 6.5. A common problem is when the soil is too alkaline...
- Magnesium deficiencyMagnesium deficiencyMagnesium deficiency is a detrimental plant disorder that occurs most often in strongly acidic, light, sandy soils, where magnesium can be easily leached away. Magnesium is an essential macronutrient found from 0.2-0.4% dry matter and is necessary for normal plant growth...
- Manganese deficiency
- Nitrogen deficiencyNitrogen deficiencyAll plants require sufficient supplies of macronutrients for healthy growth, and nitrogen is a nutrient that is commonly in limited supply. Nitrogen deficiency in plants can occur when organic matter with high carbon carbon content, such as sawdust, is added to soil. Soil organisms use any...
- Phosphorus deficiencyPhosphorus deficiencyPhosphorus deficiency is a plant disorder that is most common in areas of high rainfall, especially on acid, clay or poor chalk soils. Cold weather can cause a temporary deficiency....
- Potassium deficiencyPotassium deficiency (plants)-Soil type and potassium deficiency:Potassium deficiency, also known as potash deficiency, is a plant disorder that is most common on light, sandy soils, because potassium ions are highly soluble and will easily leach from soils without colloids. Potassium deficiency is also common in chalky or...
- Shortage of trace elementTrace elementIn analytical chemistry, a trace element is an element in a sample that has an average concentration of less than 100 parts per million measured in atomic count, or less than 100 micrograms per gram....
s such as molybdenumMolybdenumMolybdenum , is a Group 6 chemical element with the symbol Mo and atomic number 42. The name is from Neo-Latin Molybdaenum, from Ancient Greek , meaning lead, itself proposed as a loanword from Anatolian Luvian and Lydian languages, since its ores were confused with lead ores...
can also cause disorders such as whiptail in cauliflowerCauliflowerCauliflower is one of several vegetables in the species Brassica oleracea, in the family Brassicaceae. It is an annual plant that reproduces by seed...
.