Phytogeography or botanical geography is the branch of biogeography, concerned with the geographic distribution of plant species and their influence on the earth's surface. Phytogeography is concerned with all aspects of plant distribution, from the controls on the distribution of individual species ranges to the factors that govern the composition of entire communities and floras. Geobotany, by contrast, focuses on the geographic space's influence on plants. Phytogeography is part of a more general science known as biogeography. Phytogeographers are concerned with patterns and process in plant distribution. Most of the major questions and kinds of approaches taken to answer such questions are held in common between phyto- and zoogeographers. Phytogeography in wider sense encompasses four fields, according with the focused aspect, flora and origin, respectively: plant ecology. Historical plant geography Phytogeography is divided into two main branches: ecological phytogeography and historical phytogeography.
The former investigates the role of current day biotic and abiotic interactions in influencing plant distributions. The basic data elements of phytogeography are occurrence records with operational geographic units such as political units or geographical coordinates; these data are used to construct phytogeographic provinces and elements. The questions and approaches in phytogeography are shared with zoogeography, except zoogeography is concerned with animal distribution rather than plant distribution; the term phytogeography. How the term is applied by practicing scientists is apparent in the way periodicals use the term; the American Journal of Botany, a monthly primary research journal publishes a section titled "Systematics and Evolution." Topics covered in the American Journal of Botany's "Systematics and Phytogeography" section include phylogeography, distribution of genetic variation and, historical biogeography, general plant species distribution patterns. Biodiversity patterns are not covered.
Phytogeography has a long history. One of the subjects earliest proponents was Prussian naturalist Alexander von Humboldt, referred to as the "father of phytogeography". Von Humboldt advocated a quantitative approach to phytogeography that has characterized modern plant geography. Gross patterns of the distribution of plants became apparent early on in the study of plant geography. For example, Alfred Russel Wallace, co-discoverer of the principle of natural selection, discussed the Latitudinal gradients in species diversity, a pattern observed in other organisms as well. Much research effort in plant geography has since been devoted to understanding this pattern and describing it in more detail. In 1890, the United States Congress passed an act that appropriated funds to send expeditions to discover the geographic distributions of plants in the United States; the first of these was The Death Valley Expedition, including Frederick Vernon Coville, Frederick Funston, Clinton Hart Merriam, others.
Research in plant geography has been directed to understanding the patterns of adaptation of species to the environment. This is done chiefly by describing geographical patterns of trait/environment relationships; these patterns termed ecogeographical rules when applied to plants represent another area of phytogeography. A new field termed macroecology has developed, which focuses on broad-scale patterns and phenomena in ecology. Macroecology focuses as much on other organisms as plants. Floristics is a study of the flora of some area. Traditional phytogeography concerns itself with floristics and floristic classification, see floristic province. Biogeography Botany Geobotanical prospecting Macroecology Species distribution Zoogeography Association Brown, James H.. "Chapter 1". Biogeography. Sunderland, Massachusetts: Sinauer Associates. ISBN 0878930736. Humbodlt, Alexander von. Essai sur la geographie des plantes. Accompagné d'un tableau physique des régions équinoxiales fondé sur des mesures exécutées, depuis le dixiéme degré de latitude boréale jusqu'au dixiéme degré de latitude australe, pendant les années 1799, 1800, 1801, 1802 et 1803.
Paris: Schöll. Polunin, Nicholas. Introduction to Plant Geography and Some Related Sciences. McGraw-Hill. Wallace, Alfred R.. Tropical Nature, Other Essays. London: Macmillan. Clements, Frederic E.. "Plant Geography". Encyclopedia Americana. "Distribution of Plants". New International Encyclopedia. 1905
Plant anatomy or phytotomy is the general term for the study of the internal structure of plants. It included plant morphology, the description of the physical form and external structure of plants, but since the mid-20th century plant anatomy has been considered a separate field referring only to internal plant structure. Plant anatomy is now investigated at the cellular level, involves the sectioning of tissues and microscopy. Although some plant anatomy studies utilize a systems approach, such as the study of vascular tissues, plant anatomy is more classically divided into the following structural categories: Flower anatomy Calyx Corolla Androecium Gynoecium Leaf anatomy Epidermis Palisade cells Stem anatomy Stem structure Fruit/Seed anatomy Ovule Seed structure Pericarp Accessory fruit Wood anatomy Bark Cork Phloem Vascular cambium Heartwood and sapwood branch collar Root anatomy Root structure About 300 BC Theophrastus wrote a number of plant treatises, only two of which survive, Enquiry into Plants, On the Causes of Plants.
He developed concepts of plant morphology and classification, which did not withstand the scientific scrutiny of the Renaissance. A Swiss physician and botanist, Gaspard Bauhin, introduced binomial nomenclature into plant taxonomy, he published Pinax theatri botanici in 1596, the first to use this convention for naming of species. His criteria for classification included natural relationships, or'affinities', which in many cases were structural, it was in the late 1600s. Italian doctor and microscopist, Marcello Malpighi, was one of the two founders of plant anatomy. In 1671 he published his Anatomia Plantarum, the first major advance in plant physiogamy since Aristotle; the other founder was the British doctor Nehemiah Grew. He published An Idea of a Philosophical History of Plants in 1672 and The Anatomy of Plants in 1682. Grew is credited with the recognition of plant cells, although he called them'vesicles' and'bladders', he identified and described the sexual organs of plants and their parts.
In the eighteenth century, Carl Linnaeus established taxonomy based on structure, his early work was with plant anatomy. While the exact structural level, to be considered to be scientifically valid for comparison and differentiation has changed with the growth of knowledge, the basic principles were established by Linnaeus, he published his master work, Species Plantarum in 1753. In 1802, French botanist Charles-François Brisseau de Mirbel, published Traité d'anatomie et de physiologie végétale establishing the beginnings of the science of plant cytology. In 1812, Johann Jacob Paul Moldenhawer published Beyträge zur Anatomie der Pflanzen, describing microscopic studies of plant tissues. In 1813 a Swiss botanist, Augustin Pyrame de Candolle, published Théorie élémentaire de la botanique, in which he argued that plant anatomy, not physiology, ought to be the sole basis for plant classification. Using a scientific basis, he established structural criteria for defining and separating plant genera.
In 1830, Franz Meyen published the first comprehensive review of plant anatomy. In 1838 German botanist Matthias Jakob Schleiden, published Contributions to Phytogenesis, stating, "the lower plants all consist of one cell, while the higher plants are composed of individual cells" thus confirming and continuing Mirbel's work. A German-Polish botanist, Eduard Strasburger, described the mitotic process in plant cells and further demonstrated that new cell nuclei can only arise from the division of other pre-existing nuclei, his Studien über Protoplasma was published in 1876. Gottlieb Haberlandt, a German botanist, studied plant physiology and classified plant tissue based upon function. On this basis, in 1884 he published Physiologische Pflanzenanatomie in which he described twelve types of tissue systems. British paleobotanists Dunkinfield Henry Scott and William Crawford Williamson described the structures of fossilized plants at the end of the nineteenth century. Scott's Studies in Fossil Botany was published in 1900.
Following Charles Darwin's Origin of Species a Canadian botanist, Edward Charles Jeffrey, studying the comparative anatomy and phylogeny of different vascular plant groups, applied the theory to plants using the form and structure of plants to establish a number of evolutionary lines. He published his The Anatomy of Woody Plants in 1917; the growth of comparative plant anatomy was spearheaded by British botanist Agnes Arber. She published Water Plants: A Study of Aquatic Angiosperms in 1920, Monocotyledons: A Morphological Study in 1925, The Gramineae: A Study of Cereal and Grass in 1934. Following World War II, Katherine Esau published, Plant Anatomy, which became the definitive textbook on plant structure in North American universities and elsewhere, it was still in print as of 2006, she followed up with her Anatomy of seed plants in 1960. Plant morphology Plant physiology Eames, Arthur Johnson. An Introduction to Plant Anatomy 2nd ed. McGraw-Hill, New York, link. Esau, Katherine. Plant Anatomy 2nd ed. Wiley, New York.
Meicenheimer, R. History of Plant Anatomy. Miami University, link. Cutler, D. F.. Anatomy of the Monocotyledons. 10 vols. Oxford University Press. Goffinet, B.. Morphology and classification of the Bryophyta. In: Goffinet, B.. Bryophyte Biology, 2nd ed. Cambridge University Press, pp. 55-138. Jeffrey, E. C.. The anatomy of w
A pedicel is a stem that attaches a single flower to the inflorescence. In the absence of a pedicel, the flowers are described as sessile. Pedicel is applied to the stem of the infructescence; the word "pedicel" is derived from the latin pediculus, meaning "little foot". The stem or branch from the main stem of the inflorescence that holds a group of pedicels is called a peduncle. In Halloween types of pumpkin or squash plants, the shape of the pedicel has received particular attention because plant breeders are trying to optimize the size and shape of the pedicel for the best "lid" for a "jack-o'-lantern". Sessile Scape Terminology for Asteraceae
Parsley or garden parsley is a species of flowering plant in the family Apiaceae, native to the central Mediterranean region, but has naturalized elsewhere in Europe, is cultivated as a herb, a spice, a vegetable. Where it grows as a biennial, in the first year, it forms a rosette of tripinnate leaves, 10–25 cm long, with numerous 1–3 cm leaflets and a taproot used as a food store over the winter. In the second year, it grows a flowering stem with sparser leaves and umbels with yellow to yellowish-green flowers. Parsley is used in European, Middle Eastern, American cuisine. Curly leaf parsley is used as a garnish. In central Europe, eastern Europe, southern Europe, as well as in western Asia, many dishes are served with fresh green chopped parsley sprinkled on top. Flat leaf parsley is similar, but it is easier to cultivate, some say it has a stronger flavor. Root parsley is common in central and southern European cuisines, where it is used as a snack or a vegetable in many soups and casseroles.
The word "parsley" is a merger of Old English petersilie and the Old French peresil, both derived from Medieval Latin petrosilium, from Latin petroselinum, the latinization of the Greek πετροσέλινον, "rock-celery", from πέτρα, "rock, stone", + σέλινον, "celery". Mycenaean Greek se-ri-no, in Linear B, is the earliest attested form of the word selinon. Garden parsley is a bright green, biennial plant in temperate climates, or an annual herb in subtropical and tropical areas. Where it grows as a biennial, in the first year, it forms a rosette of tripinnate leaves 10–25 cm long with numerous 1–3 cm leaflets, a taproot used as a food store over the winter. In the second year, it grows a flowering stem to 75 cm tall with sparser leaves and flat-topped 3–10 cm diameter umbels with numerous 2 mm diameter yellow to yellowish-green flowers; the seeds are ovoid, 2–3 mm long, with prominent style remnants at the apex. One of the compounds of the essential oil is apiol; the plant dies after seed maturation.
Parsley is a source of flavonoids and antioxidants luteolin, folic acid, vitamin K, vitamin C, vitamin A. Half a tablespoon of dried parsley contains about 6.0 µg of lycopene and 10.7 µg of alpha carotene as well as 82.9 µg of lutein+zeaxanthin and 80.7 µg of beta carotene. Excessive consumption of parsley should be avoided by pregnant women. Normal food quantities are safe for pregnant women, but consuming excessively large amounts may have uterotonic effects. Parsley grows best in well-drained soil, with full sun, it grows best between 22–30 °C, is grown from seed. Germination is slow, taking four to six weeks, it is difficult because of furanocoumarins in its seed coat. Plants grown for the leaf crop are spaced 10 cm apart, while those grown as a root crop are spaced 20 cm apart to allow for the root development. Parsley attracts several species of wildlife; some swallowtail butterflies use parsley as a host plant for their larvae. Bees and other nectar-feeding insects visit the flowers. Birds such as the goldfinch feed on the seeds.
In cultivation, parsley is subdivided into several cultivar groups, depending on the form of the plant, related to its end use. These are treated as botanical varieties, but they are cultivated selections, not of natural botanical origin; the two main groups of parsley used as herbs are curly leaf. Of these, the neapolitanum group more resembles the natural wild species. Flat-leaved parsley is preferred by some gardeners as it is easier to cultivate, being more tolerant of both rain and sunshine, is said to have a stronger flavor — although this is disputed — while curly leaf parsley is preferred by others because of its more decorative appearance in garnishing. A third type, sometimes grown in southern Italy, has thick leaf. Another type of parsley is grown as the Hamburg root parsley; this type of parsley produces much thicker roots than types cultivated for their leaves. Although used in Britain and the United States, root parsley is common in central and eastern European cuisine, where it is used in soups and stews, or eaten raw, as a snack.
Although root parsley looks similar to the parsnip, among its closest relatives in the family Apiaceae, its taste is quite different. Parsley is used in Middle Eastern, European and American cooking. Curly leaf parsley is used as a garnish. Green parsley is used as a garnish on potato dishes, on rice dishes, on fish, fried chicken, lamb and steaks, as well in meat or vegetable stews. In central Europe, eastern Europe, southern Europe, as well as in western Asia, many dishes are served with fresh green, chopped parsley sprinkled on top. In southern and central Europe, parsley is part of bouquet garni, a bundle of fresh herbs used as an ingredient in stocks and sauces. Freshly chopped green parsley is used as a topping for soups such as chicken soup, green salads, or s
Dill is an annual herb in the celery family Apiaceae. It is the only species in the genus Anethum. Dill is grown in Eurasia where its leaves and seeds are used as a herb or spice for flavouring food. Dill grows up to 40–60 cm, with slender hollow stems and alternate, finely divided delicate leaves 10–20 cm long; the ultimate leaf divisions are 1–2 mm broad broader than the similar leaves of fennel, which are threadlike, less than 1 mm broad, but harder in texture. The flowers are white to yellow, in small umbels 2–9 cm diameter; the seeds are 4–5 mm long and 1 mm thick, straight to curved with a longitudinally ridged surface. The word "dill" and its close relatives are found in most of the Germanic languages; the generic name Anethum is the Latin form of the Greek ἄνῑσον / ἄνησον / ἄνηθον / ἄνητον, which meant both "dill" and "anise". The form anīsum came to be used for anēthum for dill; the Latin word is the origin of dill's names in the Western Romance languages, of the obsolete English anet. Most Slavic language names come from Proto-Slavic *koprъ.
Fresh and dried dill leaves are used as herbs in Europe and central Asia. Like caraway, the fernlike leaves of dill are aromatic and are used to flavor many foods such as gravlax and other fish dishes and other soups, as well as pickles. Dill is best when used fresh, as it loses its flavor if dried, freeze-dried dill leaves retain their flavor well for a few months. Dill oil is extracted from the leaves and seeds of the plant; the oil from the seeds is used in the manufacturing of soaps. Dill is the eponymous ingredient in dill pickles. In central, eastern Europe, Baltic states, Ukraine and Finland dill is a popular culinary herb used in the kitchen along with chives or parsley. Fresh, finely cut dill leaves are used as a topping in soups the hot red borsht and the cold borsht mixed with curds, yogurt, or sour cream, served during hot summer weather and is called okroshka, it is popular in summer to drink fermented milk mixed with dill. In the same way, prepared dill is used as a topping for boiled potatoes covered with fresh butter – in summer when there are so-called "new", or young, potatoes.
The dill leaves may be mixed with butter, making a dill butter. Dill leaves mixed with tvorog, form one of the traditional cheese spreads used for sandwiches. Fresh dill leaves are used throughout the year as an ingredient in salads, e.g. one made of lettuce, fresh cucumbers, tomatoes, as basil leaves are used in Italy and Greece. Russian cuisine is noted for liberal use of dill, its supposed antiflatulent activity caused some Russian cosmonauts to recommend its use in manned spaceflight due to the confined quarters and closed air supply. In Polish cuisine, fresh dill leaves mixed with sour cream are the basis for dressings, it is popular to use this kind of sauce with freshly cut cucumbers, which are wholly immersed in the sauce, making a salad called mizeria. The dill leaves serve as a basis for cooking dill sauce, used hot for baked freshwater fish and for chicken or turkey breast, or used hot or cold for hard-boiled eggs. A dill-based soup, served with potatoes and hard-boiled eggs, is popular in Poland.
Whole stems including roots and flower buds are used traditionally to prepare Polish-style pickled cucumbers the so-called low-salt cucumbers. Whole stems of dill are cooked with potatoes the potatoes of autumn and winter, so they resemble the flavor of the newer potatoes found in summer; some kinds of fish trout and salmon, traditionally are baked with the stems and leaves of dill. In the Czech Republic, white dill sauce made of cream, flour and dill is called koprová omáčka and is served either with boiled eggs and potatoes, or with dumplings and boiled beef. Another Czech dish with dill is a soup called, that contains mushrooms. In Germany, dill is popular as a seasoning for fish and many other dishes, chopped as a garnish on potatoes, as a flavoring in pickles. In the UK, dill may be used in fish pie In Bulgaria dill is used in traditional vegetable salads, most notably the yogurt-based cold soup Tarator, it is used in the preparation of sour pickles and other dishes. In Romania dill is used as an ingredient for soups such as borş, other dishes those based on peas and cabbage.
It may be found in many summer salads. During springtime, it is used in omelets with spring onions, it complements sauces based on sour cream or yogurt and is mixed with salted cheese and used as a filling. Another popular dish with dill as a main ingredient is dill sauce, served with eggs and fried sausages. In Hungary, dill is widely used, it is popular as a sauce or filling, mixed with a type of cottage cheese. Dill is used for pickling and in salads; the Hungarian name for dill is kapor. In Serbia, dill is known as mirodjija and is used as an addition to soups and cucumber salads, French fries, it features in the Serbian prove
The carrot is a root vegetable orange in colour, though purple, red and yellow cultivars exist. Carrots are a domesticated form of the wild carrot, Daucus carota, native to Europe and southwestern Asia; the plant originated in Persia and was cultivated for its leaves and seeds. The most eaten part of the plant is the taproot, although the stems and leaves are eaten as well; the domestic carrot has been selectively bred for its enlarged, more palatable, less woody-textured taproot. The carrot is a biennial plant in the umbellifer family Apiaceae. At first, it grows a rosette of leaves while building up the enlarged taproot. Fast-growing cultivars mature within three months of sowing the seed, while slower-maturing cultivars need a month longer; the roots contain high quantities of alpha- and beta-carotene, are a good source of vitamin K and vitamin B6, but the belief that eating carrots improves night vision is a myth put forward by the British in World War II to mislead the enemy about their military capabilities.
The United Nations Food and Agriculture Organization reports that world production of carrots and turnips for the calendar year 2013 was 37.2 million tonnes. Carrots are used in many cuisines in the preparation of salads, carrot salads are a tradition in many regional cuisines; the word is first recorded in English circa 1530 and was borrowed from Middle French carotte, itself from Late Latin carōta, from Greek καρωτόν or karōton from the Indo-European root *ker-, due to its horn-like shape. In Old English, carrots were not distinguished from parsnips: the two were collectively called moru or more. Various languages still use the same word for "carrot" as they do for "root". Both written history and molecular genetic studies indicate that the domestic carrot has a single origin in Central Asia, its wild ancestors originated in Persia, which remains the centre of diversity for the wild carrot Daucus carota. A occurring subspecies of the wild carrot was bred selectively over the centuries to reduce bitterness, increase sweetness and minimise the woody core.
When they were first cultivated, carrots were grown for their aromatic leaves and seeds rather than their roots. Carrot seeds have been found in Switzerland and Southern Germany dating back to 2000–3000 BC; some close relatives of the carrot are still grown for their leaves and seeds, such as parsley, coriander, anise and cumin. The first mention of the root in classical sources is from the 1st century AD; the plant is depicted and described in the Eastern Roman Juliana Anicia Codex, a 6th-century AD Constantinopolitan copy of the Greek physician Dioscorides' 1st-century pharmacopoeia of herbs and medicines, De Materia Medica. Three different types of carrots are depicted, the text states that "the root can be cooked and eaten"; the plant was introduced into Spain by the Moors in the 8th century. In the 10th century, roots from West Asia and Europe were purple; the modern carrot originated in Afghanistan at about this time. The 11th-century Jewish scholar Simeon Seth describes both red and yellow carrots, as does the 12th-century Arab-Andalusian agriculturist, Ibn al-'Awwam.
Cultivated carrots appeared in China in the 14th century, in Japan in the 18th century. There are many claims that Dutch growers created orange carrots in the 17th century to honor the Dutch flag at the time. Other authorities argue. Modern carrots were described at about this time by the English antiquary John Aubrey: "Carrots were first sown at Beckington in Somersetshire; some old Man there did remember their first bringing hither." European settlers introduced the carrot to colonial America in the 17th century. Outwardly purple carrots, still orange on the inside, were sold in British stores beginning in 2002. Daucus carota is a biennial plant. In the first year, its rosette of leaves produces large amounts of sugars, which are stored in the taproot to provide energy for the plant to flower in the second year. Soon after germination, carrot seedlings show a distinct demarcation between taproot and stem: the stem is thicker and lacks lateral roots. At the upper end of the stem is the seed leaf.
The first true leaf appears about 10–15 days after germination. Subsequent leaves are alternate, spirally arranged, pinnately compound, with leaf bases sheathing the stem; as the plant grows, the bases of the seed leaves, near the taproot, are pushed apart. The stem, located just above the ground, is compressed and the internodes are not distinct; when the seed stalk elongates for flowering, the tip of the stem narrows and becomes pointed, the stem extends upward to become a branched inflorescence up to 60–200 cm tall. Most of the taproot consists of an inner core. High-quality carrots have a large proportion of cortex compared to core. Although a xylem-free carrot is not possible, some cultivars have small and pigmented cores. Taproots are long and conical, although cylindrical and nearly-spherical cultivars are available
Plant pathology is the scientific study of diseases in plants caused by pathogens and environmental conditions. Organisms that cause infectious disease include fungi, bacteria, viroids, virus-like organisms, protozoa and parasitic plants. Not included are ectoparasites like insects, vertebrate, or other pests that affect plant health by eating of plant tissues. Plant pathology involves the study of pathogen identification, disease etiology, disease cycles, economic impact, plant disease epidemiology, plant disease resistance, how plant diseases affect humans and animals, pathosystem genetics, management of plant diseases. Control of plant diseases is crucial to the reliable production of food, it provides significant problems in agricultural use of land, water and other inputs. Plants in both natural and cultivated populations carry inherent disease resistance, but there are numerous examples of devastating plant disease impacts such as Irish potato famine and chestnut blight, as well as recurrent severe plant diseases like rice blast, soybean cyst nematode, citrus canker.
However, disease control is reasonably successful for most crops. Disease control is achieved by use of plants that have been bred for good resistance to many diseases, by plant cultivation approaches such as crop rotation, use of pathogen-free seed, appropriate planting date and plant density, control of field moisture, pesticide use. Across large regions and many crop species, it is estimated that diseases reduce plant yields by 10% every year in more developed settings, but yield loss to diseases exceeds 20% in less developed settings. Continuing advances in the science of plant pathology are needed to improve disease control, to keep up with changes in disease pressure caused by the ongoing evolution and movement of plant pathogens and by changes in agricultural practices. Plant diseases cause major economic losses for farmers worldwide; the Food and Agriculture Organization estimates indeed that pests and diseases are responsible for about 25% of crop loss. To solve this issue, new methods are needed to detect diseases and pests early, such as novel sensors that detect plant odours and spectroscopy and biophotonics that are able to diagnose plant health and metabolism.
Most phytopathogenic fungi belong to the Ascomycetes and the Basidiomycetes. The fungi reproduce both sexually and asexually via the production of other structures. Spores may be spread long distances by air or water. Many soil inhabiting fungi are capable of living saprotrophically, carrying out the part of their life cycle in the soil; these are facultative saprotrophs. Fungal diseases may be controlled through the use of other agriculture practices. However, new races of fungi evolve that are resistant to various fungicides. Biotrophic fungal pathogens colonize living plant tissue and obtain nutrients from living host cells. Necrotrophic fungal pathogens infect and kill host tissue and extract nutrients from the dead host cells. Significant fungal plant pathogens include: Fusarium spp. Thielaviopsis spp. Verticillium spp. Magnaporthe grisea Sclerotinia sclerotiorum Ustilago spp. smut of barley Rhizoctonia spp. Phakospora pachyrhizi Puccinia spp. Armillaria spp; the oomycetes are fungus-like organisms.
They include some of the most destructive plant pathogens including the genus Phytophthora, which includes the causal agents of potato late blight and sudden oak death. Particular species of oomycetes are responsible for root rot. Despite not being related to the fungi, the oomycetes have developed similar infection strategies. Oomycetes are capable of using effector proteins to turn off a plant's defenses in its infection process. Plant pathologists group them with fungal pathogens. Significant oomycete plant pathogens include: Pythium spp. Phytophthora spp. including the potato blight of the Great Irish Famine Some slime molds in Phytomyxea cause important diseases, including club root in cabbage and its relatives and powdery scab in potatoes. These are caused by species of Spongospora, respectively. Most bacteria that are associated with plants are saprotrophic and do no harm to the plant itself. However, a small number, around 100 known species, are able to cause disease. Bacterial diseases are much more prevalent in tropical regions of the world.
Most plant pathogenic bacteria are rod-shaped. In order to be able to colonize the plant they have specific pathogenicity factors. Five main types of bacterial pathogenicity factors are known: uses of cell wall–degrading enzymes, effector proteins and exopolysaccharides. Pathogens such as Erwinia species use cell wall–degrading enzymes to cause soft rot. Agrobacterium species change the level of auxins to cause tumours with phytohormones. Exopolysaccharides are produced by bacteria and block xylem vessels leading to the death of the plant. Bacteria control the production of pathogenicity factors via quorum sensing. Significant bacterial plant pathogens: Burkholderia Proteobacteria Xanthomonas spp. Pseudomonas spp. Pseudomonas syringae pv. tomato causes tomato plants to produce less fruit, it "continues to adapt to the tomato by minimizing its recognition by the tomato immune system." Phytoplasma and Spiroplasma are genera of bacteria that lack cell walls and are related to the mycoplasmas, which are human pathogens.
Together they are referred to