30-408: P. crystallinus P. kleinii P. longipes P. sphaerosporus P. umbonatus P. roridus Pilobolus is a genus of fungi that commonly grows on herbivore dung . The life cycle of Pilobolus begins with a black sporangium that has been discharged onto a plant substrate such as grass. A herbivorous animal such as a horse then eats the substrate, unknowingly consuming
60-457: A megasporangium that produces megaspores or a microsporangium that produces microspores. In flowering plants, these sporangia occur within the carpel and anthers, respectively. Fungi commonly produce spores during sexual and asexual reproduction. Spores are usually haploid and grow into mature haploid individuals through mitotic division of cells ( Urediniospores and Teliospores among rusts are dikaryotic). Dikaryotic cells result from
90-414: A multicellular gametophyte , which eventually goes on to produce gametes. Two gametes fuse to form a zygote , which develops into a new sporophyte. This cycle is known as alternation of generations . The spores of seed plants are produced internally, and the megaspores (formed within the ovules) and the microspores are involved in the formation of more complex structures that form the dispersal units,
120-437: A center pole. This shows that four spores shared a common origin and were initially in contact with each other forming a tetrahedron. A wider aperture in the shape of a groove may be termed a colpus . The number of colpi distinguishes major groups of plants. Eudicots have tricolpate spores (i.e. spores with three colpi). Envelope-enclosed spore tetrads are taken as the earliest evidence of plant life on land, dating from
150-449: A distance of 3 meters (10ft). For a sporangiophore less than 1cm tall, this involves acceleration from 0 to 20 km/h in only 2 μs, subjecting it to over 20,000 G , equivalent to a human being launched at 100 times the speed of sound. The orientation of the stalk towards the early morning sun apparently guarantees that the sporangium is shot some distance from the excrement, enhancing the chances that it will attach to vegetation and be eaten by
180-629: A new host. Pilobolus crystallinus Pilobolus crystallinus , commonly known as the " dung cannon " or " hat thrower ", is a species of fungus belonging to the Mucorales order. It is unique in that it adheres its spores to vegetation, so as to be eaten by grazing animals. It then passes through the animals' digestive systems and grows in their feces. Although these fungi only grow to be 2–4 cm (0.8–1.6 in) tall, they can shoot their sporangium , containing their spores , up to 2 m (6.6 ft) away. Due to an increase of pressure in
210-412: A new host. Another adaptation of Pilobolus is that the sporangium is covered in calcium oxalate crystals. Besides serving as a protective mechanism, their hydrophobic nature also leads the sporangium to flip over onto its sticky bottom after landing in a drop of dew, thus allowing it to cling to a plant substrate. Pilobolus species can be grown in artificial culture, but only when the growth medium
240-595: A putrid odour, for dispersal of fungal spores is yet another strategy, most prominently used by the stinkhorns . In Common Smoothcap moss ( Atrichum undulatum ), the vibration of sporophyte has been shown to be an important mechanism for spore release. In the case of spore-shedding vascular plants such as ferns, wind distribution of very light spores provides great capacity for dispersal. Also, spores are less subject to animal predation than seeds because they contain almost no food reserve; however they are more subject to fungal and bacterial predation. Their chief advantage
270-697: A zygote before developing further. The main difference between spores and seeds as dispersal units is that spores are unicellular, the first cell of a gametophyte, while seeds contain within them a developing embryo (the multicellular sporophyte of the next generation), produced by the fusion of the male gamete of the pollen tube with the female gamete formed by the megagametophyte within the ovule. Spores germinate to give rise to haploid gametophytes, while seeds germinate to give rise to diploid sporophytes. Vascular plant spores are always haploid . Vascular plants are either homosporous (or isosporous) or heterosporous . Plants that are homosporous produce spores of
300-473: Is supplemented with some form of chelated iron, or with sterilized herbivore dung. The forcible discharge mechanism of Pilobolus is exploited by parasitic nematodes including lungworms in the genus Dictyocaulus . Larval lungworm nematodes excreted by infected deer, elk, cattle, horses, and other hosts climb up Pilobolus sporangiophores and are discharged with the sporangium. They complete their life cycle when they and their Pilobolus vector are eaten by
330-478: Is that spores were an adaptation of early land plant species, such as embryophytes , that allowed for plants to easily disperse while adapting to their non-aquatic environment. This is particularly supported by the observation of a thick spore wall in cryptospores . These spore walls would have protected potential offspring from novel weather elements. The second more recent hypothesis is that spores were an early predecessor of land plants and formed during errors in
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#1732782400352360-451: Is that, of all forms of progeny, spores require the least energy and materials to produce. In the spikemoss Selaginella lepidophylla , dispersal is achieved in part by an unusual type of diaspore , a tumbleweed . Spores have been found in microfossils dating back to the mid-late Ordovician period. Two hypothesized initial functions of spores relate to whether they appeared before or after land plants. The heavily studied hypothesis
390-432: Is unique. It consists of a transparent stalk which rises above the excrement to end in a balloon-like subsporangial vesicle . On top of this, a single, black sporangium develops. The sporangiophore has the remarkable ability of orienting itself to point directly towards a light source. The shape and transparency of the subsporangial vesicle allow it to act as a lens , focusing light into carotenoid pigments deposited near
420-455: The life cycles of many plants , algae , fungi and protozoa . They were thought to have appeared as early as the mid-late Ordovician period as an adaptation of early land plants. Bacterial spores are not part of a sexual cycle, but are resistant structures used for survival under unfavourable conditions. Myxozoan spores release amoeboid infectious germs ("amoebulae") into their hosts for parasitic infection, but also reproduce within
450-491: The meiosis of algae , a hypothesized early ancestor of land plants. Whether spores arose before or after land plants, their contributions to topics in fields like paleontology and plant phylogenetics have been useful. The spores found in microfossils, also known as cryptospores, are well preserved due to the fixed material they are in as well as how abundant and widespread they were during their respective time periods. These microfossils are especially helpful when studying
480-408: The seeds and pollen grains. The term spore derives from the ancient Greek word σπορά spora , meaning " seed , sowing", related to σπόρος sporos , "sowing", and σπείρειν speirein , "to sow". In common parlance, the difference between a "spore" and a " gamete " is that a spore will germinate and develop into a sporeling , while a gamete needs to combine with another gamete to form
510-450: The vesicle , the sporangium can accelerate 0–45 mph in the first millimeter of its flight, which corresponds to an acceleration of 20000 g . Using a mucus-like substance found in the vesicle of the fungus, the sporangium can adhere itself onto whatever it lands, thus completing its life cycle. The basionym of this species is Hydrogera crystallina F.H. Wigg. 1780. The ability of this fungus to cause problems for florists
540-422: The base of the vesicle, which absorb the photons and allow cells to detect the light level in the direction of the lens. The developing sporangiophore grows such that the maturing sporangium is aimed directly at the light. When turgor pressure within the subsporangial vesicle builds to a sufficient level (often 7 ATM or greater), the sporangium is launched, and can travel anywhere from a couple of centimeters to
570-421: The first impression was that the black dots were aphids. This fungus normally grows beneath the surface – a sensitivity to oxygen inhibits radial growth at the hyphae . According to McVickar (1942), and later amended by Ootaki et al. (1993), the development of P. crystallinus may be divided into six stages: In stage I, the sporangiophore initially elongates at the apex, but does not rotate. In stage II,
600-569: The fluids of the ascus that lead to explosive discharge of the ascospores into the air. The forcible discharge of single spores termed ballistospores involves formation of a small drop of water ( Buller's drop ), which upon contact with the spore leads to its projectile release with an initial acceleration of more than 10,000 g . Other fungi rely on alternative mechanisms for spore release, such as external mechanical forces, exemplified by puffballs . Attracting insects, such as flies, to fruiting structures, by virtue of their having lively colours and
630-735: The fusion of two haploid gamete cells. Among sporogenic dikaryotic cells, karyogamy (the fusion of the two haploid nuclei) occurs to produce a diploid cell. Diploid cells undergo meiosis to produce haploid spores. Spores can be classified in several ways such as by their spore producing structure, function, origin during life cycle, and mobility. Below is a table listing the mode of classification, name, identifying characteristic, examples, and images of different spore species. Under high magnification , spores often have complex patterns or ornamentation on their exterior surfaces. A specialized terminology has been developed to describe features of such patterns. Some markings represent apertures, places where
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#1732782400352660-426: The hosts through the pairing of two nuclei within the plasmodium, which develops from the amoebula. In plants, spores are usually haploid and unicellular and are produced by meiosis in the sporangium of a diploid sporophyte . In some rare cases, diploid spore is also produced in some algae, or fungi. Under favourable conditions, the spore can develop into a new organism using mitotic division, producing
690-533: The mid-Ordovician (early Llanvirn, ~ 470 million years ago ), a period from which no macrofossils have yet been recovered. Individual trilete spores resembling those of modern cryptogamic plants first appeared in the fossil record at the end of the Ordovician period. In fungi, both asexual and sexual spores or sporangiospores of many fungal species are actively dispersed by forcible ejection from their reproductive structures. This ejection ensures exit of
720-399: The same size and type. Heterosporous plants, such as seed plants , spikemosses , quillworts , and ferns of the order Salviniales produce spores of two different sizes: the larger spore (megaspore) in effect functioning as a "female" spore and the smaller (microspore) functioning as a "male". Such plants typically give rise to the two kind of spores from within separate sporangia, either
750-416: The sporangiophore develops a sporangium . In stage III, after the development of the sporangium, there is a temporary cessation of growth. In stage IV, a subsporangial vesicle expands beneath the sporangium. This is followed by stage V, where the spore matures, and the region of hypha directly below the subsporangial vesicle continues elongating. Finally, in stage VI, the subsporangial vesicle bursts and throws
780-433: The sporangium as well. The Pilobolus sporangium survives the passage through the gastrointestinal tract without germinating, and emerges with the excrement . Once outside its host, spores within the sporangium germinate and grow as a mycelium within the excrement, where it is a primary colonizer. Later, the fungus fruits to produce more spores. The asexual fruiting structure (the sporangiophore) of Pilobolus species
810-552: The sporangium into the air. Scanning and transmission electron microscopy has shown that the surface of the sporangium is covered with crystals of two distinct sizes. The larger crystals enclose spines having a central pore. Pilobolus crystallinus has been reported to grow on the dung of cattle . Spores In biology , a spore is a unit of sexual (in fungi) or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of
840-407: The spores from the reproductive structures as well as travelling through the air over long distances. Many fungi thereby possess specialized mechanical and physiological mechanisms as well as spore-surface structures, such as hydrophobins , for spore ejection. These mechanisms include, for example, forcible discharge of ascospores enabled by the structure of the ascus and accumulation of osmolytes in
870-418: The tough outer coat of the spore can be penetrated when germination occurs. Spores can be categorized based on the position and number of these markings and apertures. Alete spores show no lines. In monolete spores , there is a single narrow line (laesura) on the spore. Indicating the prior contact of two spores that eventually separated. In trilete spores , each spore shows three narrow lines radiating from
900-437: Was noted in the scientific literature in 1881: ... this small fungus had proved this season to be an expensive annoyance to florists engaged in winter forcing flowers. Rose-growers especially had found it to interfere seriously with their profits. The injury was caused by the projection of the sporangia which covered the flowers and leaves of the roses as if profusely dusted with black pepper. The flowers were almost unsaleable as
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