A locule or loculus is a small cavity or compartment within an organ or part of an organism. In angiosperms, the term locule refers to a chamber within an ovary of the flower and fruits. Depending on the number of locules in the ovary, fruits can be classified as uni-locular, bi-locular, tri-locular or multi-locular; the number of locules present in a gynoecium may be equal to or less than the number of carpels. The locules contain the seeds; the term may refer to chambers within anthers containing pollen. In Ascomycete fungi, locules are chambers within the hymenium in which the perithecia develop
The gymnosperms known as Acrogymnospermae, are a group of seed-producing plants that includes conifers, cycads and gnetophytes. The term "gymnosperm" comes from the Greek composite word γυμνόσπερμος, meaning "naked seeds"; the name is based on the unenclosed condition of their seeds. The non-encased condition of their seeds stands in contrast to the seeds and ovules of flowering plants, which are enclosed within an ovary. Gymnosperm seeds develop either on the surface of scales or leaves, which are modified to form cones, or solitary as in Yew, Ginkgo; the gymnosperms and angiosperms together compose the spermatophytes or seed plants. The gymnosperms are divided into six phyla. Organisms that belong to the Cycadophyta, Ginkgophyta and Pinophyta phyla are still in existence while those in the Pteridospermales and Cordaitales phyla are now extinct. By far the largest group of living gymnosperms are the conifers, followed by cycads and Ginkgo biloba. Roots in some genera have fungal association with roots in the form of mycorrhiza, while in some others small specialised roots called coralloid roots are associated with nitrogen-fixing cyanobacteria.
The current formal classification of the living gymnosperms is the "Acrogymnospermae", which form a monophyletic group within the spermatophytes. The wider "Gymnospermae" group is thought to be paraphyletic; the fossil record of gymnosperms includes many distinctive taxa that do not belong to the four modern groups, including seed-bearing trees that have a somewhat fern-like vegetative morphology. When fossil gymnosperms such as these and the Bennettitales and Caytonia are considered, it is clear that angiosperms are nested within a larger gymnospermae clade, although which group of gymnosperms is their closest relative remains unclear; the extant gymnosperms include 12 main families and 83 genera which contain more than 1000 known species. Subclass Cycadidae Order Cycadales Family Cycadaceae: Cycas Family Zamiaceae: Dioon, Macrozamia, Encephalartos, Ceratozamia, Zamia. Subclass Ginkgoidae Order Ginkgoales Family Ginkgoaceae: GinkgoSubclass Gnetidae Order Welwitschiales Family Welwitschiaceae: Welwitschia Order Gnetales Family Gnetaceae: Gnetum Order Ephedrales Family Ephedraceae: EphedraSubclass Pinidae Order Pinales Family Pinaceae: Cedrus, Cathaya, Pseudotsuga, Pseudolarix, Nothotsuga, Abies Order Araucariales Family Araucariaceae: Araucaria, Agathis Family Podocarpaceae: Phyllocladus, Prumnopitys, Halocarpus, Lagarostrobos, Saxegothaea, Pherosphaera, Dacrycarpus, Falcatifolium, Nageia, Podocarpus Order Cupressales Family Sciadopityaceae: Sciadopitys Family Cupressaceae: Cunninghamia, Athrotaxis, Sequoia, Cryptomeria, Taxodium, Austrocedrus, Pilgerodendron, Diselma, Callitris, Thuja, Chamaecyparis, Cupressus, Xanthocyparis, Tetraclinis, Microbiota Family Taxaceae: Austrotaxus, Taxus, Amentotaxus, Torreya There are over 1000 living species of gymnosperm.
It is accepted that the gymnosperms originated in the late Carboniferous period, replacing the lycopsid rainforests of the tropical region. This appears to have been the result of a whole genome duplication event around 319 million years ago. Early characteristics of seed plants were evident in fossil progymnosperms of the late Devonian period around 383 million years ago, it has been suggested that during the mid-Mesozoic era, pollination of some extinct groups of gymnosperms was by extinct species of scorpionflies that had specialized proboscis for feeding on pollination drops. The scorpionflies engaged in pollination mutualisms with gymnosperms, long before the similar and independent coevolution of nectar-feeding insects on angiosperms. Evidence has been found that mid-Mesozoic gymnosperms were pollinated by Kalligrammatid lacewings, a now-extinct genus with members which resembled the modern butterflies that arose far later. Conifers are by far the most abundant extant group of gymnosperms with six to eight families, with a total of 65-70 genera and 600-630 species.
Conifers most are evergreens. The leaves of many conifers are long and needle-like, other species, including most Cupressaceae and some Podocarpaceae, have flat, triangular scale-like leaves. Agathis in Araucariaceae and Nageia in Podocarpaceae have flat strap-shaped leaves. Cycads are the next most abundant group of gymnosperms, with two or three families, 11 genera, 338 species. A majority of cycads are native to tropical climates and are most abundantly found in regions near the equator; the other extant groups are one species of Ginkgo. Gymnosperms have major economic uses. Pine, fir and cedar are all examples of conifers that are used for lumber, paper production, resin; some other common uses for gymnosperms are soap, nail polish, food and perfumes. Gymnosperms, like all vascular plants, have a sporophyte-dominant life cycle, which means they spend most of their life cycle with diploid cells, while
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
Bryophytes are an informal group consisting of three divisions of non-vascular land plants: the liverworts and mosses. They are characteristically limited in size and prefer moist habitats although they can survive in drier environments; the bryophytes consist of about 20,000 plant species. Bryophytes produce enclosed reproductive structures, they reproduce via spores. Bryophytes are considered to be a paraphyletic group and not a monophyletic group, although some studies have produced contrary results. Regardless of their status, the name is convenient and remains in use as an informal collective term; the term "bryophyte" comes from Greek βρύον, bryon "tree-moss, oyster-green" and φυτόν, phyton "plant". The defining features of bryophytes are: Their life cycles are dominated by the gametophyte stage Their sporophytes are unbranched They do not have a true vascular tissue containing lignin Bryophytes exist in a wide variety of habitats, they can be found growing in a range of temperatures and moisture.
Bryophytes can grow where vascularized plants cannot because they do not depend on roots for an uptake of nutrients from soil. Bryophytes can survive on bare soil. Like all land plants, bryophytes have life cycles with alternation of generations. In each cycle, a haploid gametophyte, each of whose cells contains a fixed number of unpaired chromosomes, alternates with a diploid sporophyte, whose cell contain two sets of paired chromosomes. Gametophytes produce haploid sperm and eggs which fuse to form diploid zygotes that grow into sporophytes. Sporophytes produce haploid spores by meiosis. Bryophytes are gametophyte dominant, meaning that the more prominent, longer-lived plant is the haploid gametophyte; the diploid sporophytes appear only and remain attached to and nutritionally dependent on the gametophyte. In bryophytes, the sporophytes produce a single sporangium. Liverworts and hornworts spend most of their lives as gametophytes. Gametangia and antheridia, are produced on the gametophytes, sometimes at the tips of shoots, in the axils of leaves or hidden under thalli.
Some bryophytes, such as the liverwort Marchantia, create elaborate structures to bear the gametangia that are called gametangiophores. Sperm are flagellated and must swim from the antheridia that produce them to archegonia which may be on a different plant. Arthropods can assist in transfer of sperm. Fertilized eggs become zygotes. Mature sporophytes remain attached to the gametophyte, they consist of a stalk called a single sporangium or capsule. Inside the sporangium, haploid spores are produced by meiosis; these are dispersed, most by wind, if they land in a suitable environment can develop into a new gametophyte. Thus bryophytes disperse by a combination of swimming sperm and spores, in a manner similar to lycophytes and other cryptogams; the arrangement of antheridia and archegonia on an individual bryophyte plant is constant within a species, although in some species it may depend on environmental conditions. The main division is between species in which the antheridia and archegonia occur on the same plant and those in which they occur on different plants.
The term monoicous may be used where antheridia and archegonia occur on the same gametophyte and the term dioicous where they occur on different gametophytes. In seed plants, "monoecious" is used where flowers with anthers and flowers with ovules occur on the same sporophyte and "dioecious" where they occur on different sporophytes; these terms may be used instead of "monoicous" and "dioicous" to describe bryophyte gametophytes. "Monoecious" and "monoicous" are both derived from the Greek for "one house", "dioecious" and "dioicous" from the Greek for two houses. The use of the "oicy" terminology is said to have the advantage of emphasizing the difference between the gametophyte sexuality of bryophytes and the sporophyte sexuality of seed plants. Monoicous plants are hermaphroditic, meaning that the same plant has both sexes; the exact arrangement of the antheridia and archegonia in monoicous plants varies. They may be borne on different shoots, on the same shoot but not together in a common structure, or together in a common "inflorescence".
Dioicous plants are unisexual. All four patterns occur in species of the moss genus Bryum. Traditionally, all living land plants without vascular tissues were classified in a single taxonomic group a division. More phylogenetic research has questioned whether the bryophytes form a monophyletic group and thus whether they should form a single taxon. Although a 2005 study supported the traditional view that the bryophytes form a monophyletic group, by 2010 a broad consensus had emerged among systematists that bryophytes as a whole are not a natural group, although each of the three extant groups is monophyletic; the three bryophyte clades are the Marchantiophyta and Anthocerotophyta. The vascular plants or tracheophytes form a fourth, unranked clade of land plants called the "Polysporangiophyta". In this analysis, hornworts are sister
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
Paleobotany spelled as palaeobotany, is the branch of paleontology or paleobiology dealing with the recovery and identification of plant remains from geological contexts, their use for the biological reconstruction of past environments, both the evolutionary history of plants, with a bearing upon the evolution of life in general. A synonym is paleophytology. Paleobotany includes the study of terrestrial plant fossils, as well as the study of prehistoric marine photoautotrophs, such as photosynthetic algae, seaweeds or kelp. A related field is palynology, the study of fossilized and extant spores and pollen. Paleobotany is important in the reconstruction of ancient ecological systems and climate, known as paleoecology and paleoclimatology respectively. Paleobotany has become important to the field of archaeology for the use of phytoliths in relative dating and in paleoethnobotany; the emergence of paleobotany as a scientific discipline can be seen in the early 19th century in the works of the German palaeontologist Ernst Friedrich von Schlotheim, the Czech nobleman and scholar Kaspar Maria von Sternberg, the French botanist Adolphe-Théodore Brongniart.
Macroscopic remains of true vascular plants are first found in the fossil record during the Silurian Period of the Paleozoic era. Some dispersed, fragmentary fossils of disputed affinity spores and cuticles, have been found in rocks from the Ordovician Period in Oman, are thought to derive from liverwort- or moss-grade fossil plants. An important early land plant fossil locality is the Rhynie Chert, found outside the village of Rhynie in Scotland; the Rhynie chert is an Early Devonian sinter deposit composed of silica. It is exceptional due to its preservation of several different clades of plants, from mosses and lycopods to more unusual, problematic forms. Many fossil animals, including arthropods and arachnids, are found in the Rhynie Chert, it offers a unique window on the history of early terrestrial life. Plant-derived macrofossils become abundant in the Late Devonian and include tree trunks and roots; the earliest tree was thought to be Archaeopteris, which bears simple, fern-like leaves spirally arranged on branches atop a conifer-like trunk, though it is now known to be the discovered Wattieza.
Widespread coal swamp deposits across North America and Europe during the Carboniferous Period contain a wealth of fossils containing arborescent lycopods up to 30 meters tall, abundant seed plants, such as conifers and seed ferns, countless smaller, herbaceous plants. Angiosperms evolved during the Mesozoic, flowering plant pollen and leaves first appear during the Early Cretaceous 130 million years ago. A plant fossil is any preserved part of a plant; such fossils may be prehistoric impressions that are many millions of years old, or bits of charcoal that are only a few hundred years old. Prehistoric plants are various groups of plants. Plant fossils can be preserved in a variety of ways, each of which can give different types of information about the original parent plant; these modes of preservation are discussed in the general pages on fossils but may be summarised in a palaeobotanical context as follows. Adpressions; these are the most found type of plant fossil. They provide good morphological detail of dorsiventral plant parts such as leaves.
If the cuticle is preserved, they can yield fine anatomical detail of the epidermis. Little other detail of cellular anatomy is preserved. Petrifactions; these provide fine detail of the cell anatomy of the plant tissue. Morphological detail can be determined by serial sectioning, but this is both time consuming and difficult. Moulds and casts; these only tend to preserve the more robust plant parts such as seeds or woody stems. They can provide information about the three-dimensional form of the plant, in the case of casts of tree stumps can provide evidence of the density of the original vegetation. However, they preserve any fine morphological detail or cell anatomy. A subset of such fossils are pith casts, where the centre of a stem is either hollow or has delicate pith. After death, sediment forms a cast of the central cavity of the stem; the best known examples of pith casts are in cordaites. Authigenic mineralisations; these can provide fine, three-dimensional morphological detail, have proved important in the study of reproductive structures that can be distorted in adpressions.
However, as they are formed in mineral nodules, such fossils can be of large size. Fusain. Fire destroys plant tissue but sometimes charcoalified remains can preserve fine morphological detail, lost in other modes of preservation. Fusain fossils are delicate and small, but because of their buoyancy can drift for long distances and can thus provide evidence of vegetation away from areas of sedimentation. Plant fossils always represent disarticulated parts of plants; those few examples of plant fossils that appear to be the remains of whole plants in fact are incomplete as the internal cellular tis
Monocotyledons referred to as monocots, are flowering plants whose seeds contain only one embryonic leaf, or cotyledon. They constitute one of the major groups into which the flowering plants have traditionally been divided, the rest of the flowering plants having two cotyledons and therefore classified as dicotyledons, or dicots. However, molecular phylogenetic research has shown that while the monocots form a monophyletic group or clade, the dicots do not. Monocots have always been recognized as a group, but with various taxonomic ranks and under several different names; the APG III system of 2009 recognises a clade called "monocots" but does not assign it to a taxonomic rank. The monocots include about 60,000 species; the largest family in this group by number of species are the orchids, with more than 20,000 species. About half as many species belong to the true grasses, which are economically the most important family of monocots. In agriculture the majority of the biomass produced; these include not only major grains, but forage grasses, sugar cane, the bamboos.
Other economically important monocot crops include various palms and plantains, gingers and their relatives and cardamom, pineapple, water chestnut, leeks and garlic. Many houseplants are monocot epiphytes. Additionally most of the horticultural bulbs, plants cultivated for their blooms, such as lilies, irises, cannas and tulips, are monocots; the monocots or monocotyledons have, as the name implies, a single cotyledon, or embryonic leaf, in their seeds. This feature was used to contrast the monocots with the dicotyledons or dicots which have two cotyledons. From a diagnostic point of view the number of cotyledons is neither a useful characteristic, nor is it reliable; the single cotyledon is only one of a number of modifications of the body plan of the ancestral monocotyledons, whose adaptive advantages are poorly understood, but may have been related to adaption to aquatic habitats, prior to radiation to terrestrial habitats. Monocots are sufficiently distinctive that there has been disagreement as to membership of this group, despite considerable diversity in terms of external morphology.
However, morphological features that reliably characterise major clades are rare. Thus monocots are distinguishable from other angiosperms both in terms of their uniformity and diversity. On the one hand the organisation of the shoots, leaf structure and floral configuration are more uniform than in the remaining angiosperms, yet within these constraints a wealth of diversity exists, indicating a high degree of evolutionary success. Monocot diversity includes perennial geophytes such as ornamental flowers including and succulent epiphytes, all in the lilioid monocots, major cereal grains in the grass family and forage grasses as well as woody tree-like palm trees, bamboo and bromeliads, bananas and ginger in the commelinid monocots, as well as both emergent and aroids, as well as floating or submerged aquatic plants such as seagrass. Organisation and life formsThe most important distinction is their growth pattern, lacking a lateral meristem that allows for continual growth in diameter with height, therefore this characteristic is a basic limitation in shoot construction.
Although herbaceous, some arboraceous monocots reach great height and mass. The latter include agaves, palms and bamboos; this creates challenges in water transport. Some, such as species of Yucca, develop anomalous secondary growth, while palm trees utilise an anomalous primary growth form described as establishment growth; the axis undergoes primary thickening, that progresses from internode to internode, resulting in a typical inverted conical shape of the basal primary axis. The limited conductivity contributes to limited branching of the stems. Despite these limitations a wide variety of adaptive growth forms has resulted from epiphytic orchids and bromeliads to submarine Alismatales and mycotrophic Burmanniaceae and Triuridaceae. Other forms of adaptation include the climbing vines of Araceae which use negative phototropism to locate host trees, while some palms such as Calamus manan produce the longest shoots in the plant kingdom, up to 185 m long. Other monocots Poales, have adopted a therophyte life form.
LeavesThe cotyledon, the primordial Angiosperm leaf consists of a proximal leaf base or hypophyll and a distal hyperphyll. In monocots the hypophyll tends to be the dominant part in contrast to other angiosperms. From these, considerable diversity arises. Mature monocot leaves are narrow and linear, forming a sheath