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Physiological plant disorders are caused by non-pathological conditions such as poor light, adverse weather, water-logging, phytotoxic compounds or a lack of nutrients, and affect the functioning of the plant system. Physiological disorders are distinguished from plant diseases caused by pathogens, such as a virus or fungus. 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.
Calcium (Ca) deficiency is a plant disorder that can be caused by insufficient level of biologically available 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-transpiring tissues because calcium is not transported in the phloem. This may be due to water shortages, which slow the transportation of calcium to the plant, poor uptake of calcium through the stem, or too much nitrogen in the soil.
Nitrogen deficiency is a deficiency of nitrogen in plants. This can occur when organic matter with high carbon content, such as sawdust, is added to soil. Soil organisms use any nitrogen available to break down carbon sources, making nitrogen unavailable to plants. This is known as "robbing" the soil of nitrogen. All vegetables apart from nitrogen fixing legumes are prone to this disorder.
Plant nutrition is the study of the chemical elements and compounds necessary for plant growth and reproduction, plant metabolism and their external supply. In its absence the plant is unable to complete a normal life cycle, or that the element is part of some essential plant constituent or metabolite. This is in accordance with Justus von Liebig's law of the minimum. The total essential plant nutrients include seventeen different elements: carbon, oxygen and hydrogen which are absorbed from the air, whereas other nutrients including nitrogen are typically obtained from the soil.
Fusarium wilt is a common vascular wilt fungal disease, exhibiting symptoms similar to Verticillium wilt. This disease has been investigated extensively since the early years of this century. The pathogen that causes Fusarium wilt is Fusarium oxysporum. The species is further divided into formae speciales based on host plant.
A leaf spot is a limited, discoloured, diseased area of a leaf that is caused by fungal, bacterial or viral plant diseases, or by injuries from nematodes, insects, environmental factors, toxicity or herbicides. These discoloured spots or lesions often have a centre of necrosis. Symptoms can overlap across causal agents, however differing signs and symptoms of certain pathogens can lead to the diagnosis of the type of leaf spot disease. Prolonged wet and humid conditions promote leaf spot disease and most pathogens are spread by wind, splashing rain or irrigation that carry the disease to other leaves.
Uncinula necator is a fungus that causes powdery mildew of grape. It is a common pathogen of Vitis species, including the wine grape, Vitis vinifera. The fungus is believed to have originated in North America. European varieties of Vitis vinifera are more or less susceptible to this fungus. Uncinula necator infects all green tissue on the grapevine, including leaves and young berries. It can cause crop loss and poor wine quality if untreated. The sexual stage of this pathogen requires free moisture to release ascospores from its cleistothecia in the spring. However, free moisture is not needed for secondary spread via conidia; high atmospheric humidity is sufficient. Its anamorph is called Oidium tuckeri.
Clubroot is a common disease of cabbages, broccoli, cauliflower, Brussels sprouts, radishes, turnips, stocks, wallflowers and other plants of the family Brassicaceae (Cruciferae). It is caused by Plasmodiophora brassicae, which was once considered a slime mold but is now put in the group Phytomyxea. It is the first phytomyxean for which the genome has been sequenced. It has as many as thirteen races. Gall formation or distortion takes place on latent roots and gives the shape of a club or spindle. In the cabbage such attacks on the roots cause undeveloped heads or a failure to head at all, followed often by decline in vigor or by death. It is an important disease, affecting an estimated 10% of the total cultured area worldwide.
Stunted growth, also known as stunting or linear growth failure, is defined as impaired growth and development manifested by low height-for-age. It is a primary manifestation of malnutrition and recurrent infections, such as diarrhea and helminthiasis, in early childhood and even before birth, due to malnutrition during fetal development brought on by a malnourished mother. The definition of stunting according to the World Health Organization (WHO) is for the "height-for-age" value to be less than two standard deviations of the median of WHO Child Growth Standards. Stunted growth is usually associated with poverty, unsanitary environmental conditions, maternal undernutrition, frequent illness, and/or inappropriate feeding practice and care during early years of life.
Rhizoctonia solani is a species of fungus in the order Cantharellales. Basidiocarps are thin, effused, and web-like, but the fungus is more typically encountered in its anamorphic state, as hyphae and sclerotia. The name Rhizoctonia solani is currently applied to a complex of related species that await further research. In its wide sense, Rhizoctonia solani is a facultative plant pathogen with a wide host range and worldwide distribution. It causes various plant diseases such as root rot, damping off, and wire stem. It can also form mycorrhizal associations with orchids.
Pythium irregulare is a soil borne oomycete plant pathogen. Oomycetes, also known as "water molds", are fungal-like protists. They are fungal-like because of their similar life cycles, but differ in that the resting stage is diploid, they have coenocytic hyphae, a larger genome, cellulose in their cell walls instead of chitin, and contain zoospores and oospores.
Pythium aphanidermatum is a soil borne plant pathogen. Pythium is a genus in the class Oomycetes, which are also known as water molds. Oomycetes are not true fungi, as their cell walls are made of cellulose instead of chitin, they are diploid in their vegetative state, and they form coenocytic hyphae. Also, they reproduce asexually with motile biflagelette zoospores that require water to move towards and infect a host. Sexually, they reproduce with structures called antheridia, oogonia, and oospores.
Pratylenchus penetrans is a species of nematode in the genus Pratylenchus, the lesion nematodes. It occurs in temperate regions worldwide, regions between the subtropics and the polar circles. It is an animal that inhabits the roots of a wide variety of plants and results in necrotic lesions on the roots. Symptoms of P. penetrans make it hard to distinguish from other plant pathogens; only an assay of soil can conclusively diagnose a nematode problem in the field. P. penetrans is physically very similar to other nematode species, but is characterized by its highly distinctive mouthpiece. P. penetrans uses its highly modified mouth organs to rupture the outer surface of subterranean plant root structures. It will then enter into the root interior and feed on the plant tissue inside. P. penetrans is considered to be a crop parasite and farmers will often treat their soil with various pesticides in an attempt to eliminate the damage caused by an infestation. In doing this, farmers will also eliminate many of the beneficial soil fauna, which will lead to an overall degradation of soil quality in the future. Alternative, more environmentally sustainable methods to control P. penetrans populations may be possible in certain regions.
Beet necrotic yellow vein virus (BNYVV) is a plant virus, transmitted by the plasmodiophorid Polymyxa betae. The BNYVV is a member of the genus Benyvirus and is responsible for rhizomania, a disease of sugar beet that causes proliferation of thin rootlets, and leads to a smaller tap root with reduced sugar content. Infected plants are less able to take up water, and wilting can be observed during the warm period of the year. If the infection spreads to the whole plant, vein yellowing, necrosis and yellow spots appear on the leaves, giving the virus its name.
Post-harvest losses of vegetables and fruit occur at all points in the value chain from production in the field to the food being placed on a plate for consumption. Post-harvest activities include harvesting, handling, storage, processing, packaging, transportation and marketing.
Ascochyta blights occur throughout the world and can be of significant economic importance. Three fungi contribute to the ascochyta blight disease complex of pea. Ascochyta pinodes causes Mycosphaerella blight. Ascochyta pinodella causes Ascochyta foot rot, and Ascochyta pisi causes Ascochyta blight and pod spot. Of the three fungi, Ascochyta pinodes is of the most importance. These diseases are conducive under wet and humid conditions and can cause a yield loss of up to fifty percent if left uncontrolled. The best method to control ascochyta blights of pea is to reduce the amount of primary inoculum through sanitation, crop-rotation, and altering the sowing date. Other methods—chemical control, biological control, and development of resistant varieties—may also be used to effectively control ascochyta diseases.
The Celebrity tomato cultivar is a hybrid (biology) that produces long fruit-bearing stems holding 20 or more very plump, robust tomatoes. Fruits weigh approximately 8 oz., and are 4 inches across. Plants need caging or staking, and produce fruit throughout the growing season. The celebrity tomato is a cultivar of the species Solanum lycopersicum. It is a crossbreed of the common tomato that is widely used for various culinary purposes. This tomato is of great size and is known to be resistant to most tomato diseases such as Fusarium wilt, Verticillium wilt, Tobacco mosaic virus and Root-knot nematode due to its hybrid nature. Celebrity tomatoes are highly adaptive to harsh environments and can grow in a wide range of places including dry, humid and wet regions. They are resistant to cracking and splitting which usually occurs when there is an excess of water and sugar movement in the fruits. Therefore, causing the tomato skin to grow at a slower rate compared to the expansion of the fruit. They can survive in harsh uneven rainfall. However, they are highly susceptible to colder environments and are at a higher risk of dying in regions with short growing seasons. The plants can grow up to 5 feet in height with bright red medium-sized fruits. The plants are generally very thick and grow in clusters. The tomato fruits are mostly used in the making of various salsas, salads, juices and canned food.
Environmental enteropathy is an acquired small intestinal disorder characterized by gut inflammation, reduced absorptive surface area in small intestine, and disruption of intestinal barrier function. EE is most common amongst children living in low-resource settings. Acute symptoms are typically minimal or absent. EE can lead to malnutrition, anemia, stunted growth, impaired brain development, and impaired response to oral vaccinations.
Undernutrition in children, occurs when children do not consume enough calories, protein, or micronutrients to maintain good health. It is common globally and may result in both short and long term irreversible adverse health outcomes. Undernutrition is sometimes used synonymously with malnutrition, however, malnutrition could mean both undernutrition or overnutrition. The World Health Organization (WHO) estimates that malnutrition accounts for 54 percent of child mortality worldwide, which is about 1 million children. Another estimate, also by WHO, states that childhood underweight is the cause for about 35% of all deaths of children under the age of five worldwide.
Cladosporium ear rot is a disease that affects maize. The disease is caused by the saprophytic fungus Cladosporium herbarum and is characterized by black or dark green fungal growths that cause black streaks on kernels.
References
- ↑ "Tobacco - Stunted plant growth". ephytia.inra.fr. Archived from the original on 2022-02-23. Retrieved 2022-02-23.
- ↑ "stunt | plant disease | Britannica". www.britannica.com. Archived from the original on 2022-02-27. Retrieved 2022-02-23.
- ↑ "Stunting (Plant) - an overview | ScienceDirect Topics". www.sciencedirect.com. Archived from the original on 2022-02-23. Retrieved 2022-02-23.
- ↑ Breen, Susan; Solomon, Peter S.; Bedon, Frank; Vincent, Delphine (2015). "Surveying the potential of secreted antimicrobial peptides to enhance plant disease resistance". Frontiers in Plant Science. 6: 900. doi: 10.3389/fpls.2015.00900 . ISSN 1664-462X. PMC 4621407 . PMID 26579150.
- ↑ "Stunted Growth of Vegetable Seedlings | University of Maryland Extension". extension.umd.edu. Archived from the original on 2023-02-02. Retrieved 2023-02-02.
- ↑ Support, Extension Web (2019-01-07). "Environmental factors affecting plant growth". Ag - Community Horticulture/Landscape. Archived from the original on 2024-02-16. Retrieved 2024-02-16.
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