The Saxifragales are an order of flowering plants. Their closest relatives are a large eudicot group known as the rosids by the definition of rosids given in the APG II classification system; some authors define the rosids more including Saxifragales as their most basal group. Saxifragales is one of the eight groups; the others are Gunnerales, Rosids, Berberidopsidales and Asterids. Saxifragales have an extensive fossil record; the extant members are remnants of a diverse and widespread order. The Saxifragales order, as it is now understood, is based upon the results of molecular phylogenetic studies of DNA sequences, it is not part of any of the classification systems based on plant morphology. The group is much in need of comparative anatomical study in light of the recent expansion of the family Peridiscaceae to include Medusandra, a genus that before 2009 had not been placed in Saxifragales; the order is divided into suprafamilial groups. These groups are not understood to have any particular taxonomic rank.
Saxifragales contain about 2470 species. These are distributed into 15 families, or into 12 families if Haloragaceae sensu lato is recognized as a family consisting of Haloragaceae sensu stricto, Penthorum and Aphanopetalum. About 95% of the species are in five families: Crassulaceae, Grossulariaceae and Hamamelidaceae. Most of the families are monogeneric; the number of genera in each family is: Some authors do not recognize Choristylis as a separate genus from Itea. Some authors sink Liquidambar and Semiliquidambar into Altingia, thus Altingiaceae and Iteaceae are monogeneric in some classifications. Within the Saxifragales is a suprafamilial group known as the Saxifragaceae alliance, it comprises four families: Pterostemonaceae, Iteaceae and Saxifragaceae. These have long been known to be related to each other, but the circumscription of Saxifragaceae has changed dramatically, it is now a much smaller family. Crassulaceae and Tetracarpaeaceae have long been associated with Saxifragaceae. Penthorum has been associated with Crassulaceae, but sometimes with Saxifragaceae.
Two members of the core Saxifragales had sometimes been placed near Saxifragaceae, but elsewhere. Aphanopetalum was placed in Cunoniaceae, a family in Oxalidales though there were good reasons to put it in Saxifragales. Aphanopetalum is now excluded from Cunoniaceae. Haloragaceae was thought to be a family in Myrtales, but it is no longer included in that order. Cercidiphyllaceae had for a long time been associated with Hamamelidaceae and Trochodendraceae and was thought to be closer to the latter. Cercidiphyllaceae is now known to be a member of the woody clade of Saxifragales, along with Hamamelidaceae and Daphniphyllaceae, but Trochodendraceae is in the basal eudicot order Trochodendrales. Altingiaceae was not separated from Hamamelidaceae until phylogenetic studies showed that its inclusion might make Hamamelidaceae paraphyletic; the recognition of Altingiaceae as a separate family received strong statistical support in 2008. Daphniphyllum was always thought to have an anomalous combination of characters and it was placed in several different orders before molecular phylogenetic analysis showed it to belong to Saxifragales.
Paeoniaceae possesses many unique features and its taxonomic position was for a long time controversial. The idea has long persisted. Paeoniaceae has been shown unequivocally to belong in Saxifragales, while Glaucidium is in the family Ranunculaceae; the family Peridiscaceae underwent radical shifting and recircumscription from 2003 to 2009. It consisted of two related genera and Whittonia; the APG II system placed the family in Malpighiales, based on a DNA sequence for the rbcL gene from Whittonia. This sequence turned out to be not from Whittonia, but from other plants whose DNA had contaminated the sample. After Peridiscaceae was placed in Saxifragales, it was expanded to include Soyauxia in 2007, expanded again to include Medusandra in 2009; the phylogeny shown below is based on the one published by Shuguang Jian and coauthors in 2008. All branches have 100% maximum likelihood bootstrap support except where labeled with bootstrap percentage. Monogeneric families are represented by genus names.
Plant order classification at: Saxifragales Trees At: Angiosperm Phylogeny Website At: Missoure Botanical Garden Website Saxifragales At: Angiosperm Phylogeny Website Wurdack, Kenneth J.. "Malpighiales phylogenetics: Gaining ground on one of the most recalcitrant clades in the angiosperm tree of life". American Journal of Botany. 96: 1551–70. Doi:10.3732/ajb.0800207. PMID 21628300. Jian, Shuguang. "Resolving an ancient, rapid radiation in Saxifragales". Systematic Biology. 57: 38–57. Doi:10.1080/10635150801888871. PMID 18275001. Kubitzki, Klaus, ed.. Flowering Plants. Eudicots: Berberidopsidales, Crossosomatales, Fabales p.p. Geraniales, Myrtales p.p. Proteales, Vitales, Clusiaceae Alliance, Passifloraceae Alliance, Huaceae, Sabiaceae; the Families and Genera of Vascular Plants. IX. Springer. ISBN 978-3-540-32219-1
Chloroplasts are organelles that conduct photosynthesis, where the photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, stores it in the energy-storage molecules ATP and NADPH while freeing oxygen from water in plant and algal cells. They use the ATP and NADPH to make organic molecules from carbon dioxide in a process known as the Calvin cycle. Chloroplasts carry out a number of other functions, including fatty acid synthesis, much amino acid synthesis, the immune response in plants; the number of chloroplasts per cell varies from one, in unicellular algae, up to 100 in plants like Arabidopsis and wheat. A chloroplast is a type of organelle known as a plastid, characterized by its two membranes and a high concentration of chlorophyll. Other plastid types, such as the leucoplast and the chromoplast, contain little chlorophyll and do not carry out photosynthesis. Chloroplasts are dynamic—they circulate and are moved around within plant cells, pinch in two to reproduce.
Their behavior is influenced by environmental factors like light color and intensity. Chloroplasts, like mitochondria, contain their own DNA, thought to be inherited from their ancestor—a photosynthetic cyanobacterium, engulfed by an early eukaryotic cell. Chloroplasts cannot be made by the plant cell and must be inherited by each daughter cell during cell division. With one exception, all chloroplasts can be traced back to a single endosymbiotic event, when a cyanobacterium was engulfed by the eukaryote. Despite this, chloroplasts can be found in an wide set of organisms, some not directly related to each other—a consequence of many secondary and tertiary endosymbiotic events; the word chloroplast is derived from the Greek words chloros, which means green, plastes, which means "the one who forms". The first definitive description of a chloroplast was given by Hugo von Mohl in 1837 as discrete bodies within the green plant cell. In 1883, A. F. W. Schimper would name these bodies as "chloroplastids".
In 1884, Eduard Strasburger adopted the term "chloroplasts". Chloroplasts are one of many types of organelles in the plant cell, they are considered to have originated from cyanobacteria through endosymbiosis—when a eukaryotic cell engulfed a photosynthesizing cyanobacterium that became a permanent resident in the cell. Mitochondria are thought to have come from a similar event, where an aerobic prokaryote was engulfed; this origin of chloroplasts was first suggested by the Russian biologist Konstantin Mereschkowski in 1905 after Andreas Schimper observed in 1883 that chloroplasts resemble cyanobacteria. Chloroplasts are only found in plants and the amoeboid Paulinella chromatophora. Cyanobacteria are considered the ancestors of chloroplasts, they are sometimes called blue-green algae though they are prokaryotes. They are a diverse phylum of bacteria capable of carrying out photosynthesis, are gram-negative, meaning that they have two cell membranes. Cyanobacteria contain a peptidoglycan cell wall, thicker than in other gram-negative bacteria, and, located between their two cell membranes.
Like chloroplasts, they have thylakoids within. On the thylakoid membranes are photosynthetic pigments, including chlorophyll a. Phycobilins are common cyanobacterial pigments organized into hemispherical phycobilisomes attached to the outside of the thylakoid membranes. Somewhere around 1 to 2 billion years ago, a free-living cyanobacterium entered an early eukaryotic cell, either as food or as an internal parasite, but managed to escape the phagocytic vacuole it was contained in; the two innermost lipid-bilayer membranes that surround all chloroplasts correspond to the outer and inner membranes of the ancestral cyanobacterium's gram negative cell wall, not the phagosomal membrane from the host, lost. The new cellular resident became an advantage, providing food for the eukaryotic host, which allowed it to live within it. Over time, the cyanobacterium was assimilated, many of its genes were lost or transferred to the nucleus of the host. From genomes that originally contained over 3000 genes only about 130 genes remain in the chloroplasts of contemporary plants.
Some of its proteins were synthesized in the cytoplasm of the host cell, imported back into the chloroplast. Separately, somewhere around 500 million years ago, it happened again and led to the amoeboid Paulinella chromatophora; this event is called endosymbiosis, or "cell living inside another cell with a mutual benefit for both". The external cell is referred to as the host while the internal cell is called the endosymbiont. Chloroplasts are believed to have arisen after mitochondria, since all eukaryotes contain mitochondria, but not all have chloroplasts; this is called serial endosymbiosis—an early eukaryote engulfing the mitochondrion ancestor, some descendants of it engulfing the chloroplast ancestor, creating a cell with both chloroplasts and mitochondria. Whether or not primary chloroplasts came from a single endosymbiotic event, or many independent engulfments across various eukaryotic lineages, has long been debated, it is now held that organisms with primary chloroplasts share a single ancestor that took in a cyanobacterium 600–2000 million years ago.
It has been proposed. The exception is the amoeboid Paulinella chromatophora, which descends from an ancestor that took in a Prochlorococcus cyanobacterium 90–500 million years ago; these chloroplasts
Ranunculales is an order of flowering plants. Of necessity it contains the family Ranunculaceae, the buttercup family, because the name of the order is based on the name of a genus in that family. Ranunculales belongs to a paraphyletic group known as the basal eudicots, it is the most basal clade in this group. Known members include poppies and buttercups; the term Ranales was used to include the Ranunculaceae and related families, as described by Bentham and Hooker. This became replaced with Ranunculales by Melchior in 1964; the Cronquist system recognised the order, but placed it in the subclass Magnoliidae, in class Magnoliopsida. It used this circumscription: order Ranunculales family Ranunculaceae family Circaeasteraceae family Berberidaceae family Sargentodoxaceae family Lardizabalaceae family Menispermaceae family Coriariaceae family SabiaceaeIn the Cronquist system, the Papaveraceae and Fumariaceae were treated as a separate order Papaverales, placed in this same subclass Magnoliidae; the Cronquist circumscription of Ranunculales is now known to be polyphyletic.
Sabiaceae is in a clade of basal eudicots separate from Ranunculales. Coriariaceae is now placed in the order Cucurbitales; the Angiosperm Phylogeny Group recognized seven families in Ranunculales in their APG III system, published in 2009. In the preceding APG II system, they offered the option of three segregate families. Order Ranunculales family Berberidaceae family Circaeasteraceae family Eupteleaceae family Lardizabalaceae family Menispermaceae family Papaveraceae family RanunculaceaeNote: "+..." = optionally separate family. Under this definition, well-known members of Ranunculales include buttercups, columbines and poppies. A phylogeny of Ranunculales was published in 2009, based on molecular phylogenetic analysis of DNA sequences; the authors of this paper revised the tribes of the order. This is reflected in the subsequent revision of the APG, APG IV; the analysis revealed that the order consisted of three clades, Papaveraceae and a third clade, considered to be the "core" Ranuculales, consisting of the remaining five families.
The phylogeny of the families is shown in the cladogram. The fossil form Leefructus, described in 2011, has been recognized as a member of this order. Leefructus mirus shows developed leaves; the fossil is dated to 125 million years old and it not only proves that Ranunculales is an ancient group of eudicots but demonstrates that the whole angiosperm clade may be older than expected. The structure of the plant and its age may lead to a new approach regarding the field that studies the evolution of flowering plants; the fact that Leefructus shows a well-developed structure similar to modern ranunculids suggests that this group of eudicots may have developed earlier than the age of the fossil. NCBI Taxonomy Browser
Euptelea is a genus of two species of flowering plants in the monogeneric family Eupteleaceae. The genus is found from Assam east through China to Japan, consists of shrubs or small trees: Euptelea pleiosperma Euptelea polyandraThe genus was placed in the family Trochodendraceae, but the family Eupteleaceae has been recognized by many taxonomists; the APG IV system, places it in the order Ranunculales, in the clade eudicots. The family consists of a single genus Euptelea, with two species, native to eastern Asia. Euptelea polyandra is used as a food plant by the larvae of some Lepidoptera species including the engrailed; the flowers lack petals. The anthers are basifixed, the leaves are arranged in whorls. Floral Morphology in Euptelea doi:10.1093/aob/mcm106 Eupteleaceae in L. Watson and M. J. Dallwitz; the families of flowering plants. Flora of China: Eupteleaceae NCBI Taxonomy Browser links at CSDL, Texas
Fossilworks is a portal which provides query and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. Fossilworks is housed at Macquarie University, it includes many analysis and data visualization tools included in the Paleobiology Database. "Fossilworks". Retrieved 2010-04-08
APG II system
The APG II system of plant classification is the second, now obsolete, version of a modern molecular-based, system of plant taxonomy, published in April 2003 by the Angiosperm Phylogeny Group. It was a revision of the first APG system, published in 1998, was superseded in 2009 by a further revision, the APG III system. APG II was published as: Angiosperm Phylogeny Group. "An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG II". Botanical Journal of the Linnean Society 141: 399-436; each of the APG systems represents the broad consensus of a number of systematic botanists, united in the APG, working at several institutions worldwide. The APG II system recognized 45 orders, five more than the APG system; the new orders were Austrobaileyales, Gunnerales and Crossosomatales, all of which were families unplaced as to order, although contained in supra-ordinal clades, in the APG system. APG II recognized five fewer than the APG system. Thirty-nine of the APG II families were not placed in any order, but 36 of the 39 were placed in a supra-ordinal clade within the angiosperms.
Fifty-five of the families came to be known as "bracketed families". They were optional segregates of families; the APG II system was adopted in whole or in part in a number of references. It was superseded 6½ years by the APG III system, published in October 2009. Main groups in the system: angiosperms: magnoliids monocots commelinids eudicots core eudicots rosids eurosids I eurosids II asterids euasterids I euasterids IIShown below is the classification in full detail, except for the fifteen genera and three families that were unplaced in APG II; the unplaced taxa were listed at the end of the appendix in a section entitled "Taxa of Uncertain Position". Under some of the clades are listed the families that were placed incertae sedis in that clade. Thirty-six families were so placed; this means. Paraphyletic grade basal angiosperms family Amborellaceae family Chloranthaceae family Nymphaeaceae order Austrobaileyales order Ceratophyllales clade magnoliids order Canellales order Laurales order Magnoliales order Piperales clade monocots family Petrosaviaceae order Acorales order Alismatales order Asparagales order Dioscoreales order Liliales order Pandanales clade commelinids family Dasypogonaceae order Arecales order Commelinales order Poales order Zingiberales clade eudicots family Buxaceae family Sabiaceae family Trochodendraceae order Proteales order Ranunculales clade core eudicots family Aextoxicaceae family Berberidopsidaceae family Dilleniaceae order Gunnerales order Caryophyllales order Santalales order Saxifragales clade rosids family Aphloiaceae family Geissolomataceae family Ixerbaceae family Picramniaceae family Strasburgeriaceae family Vitaceae order Crossosomatales order Geraniales order Myrtales clade eurosids I family Zygophyllaceae family Huaceae order Celastrales order Cucurbitales order Fabales order Fagales order Malpighiales order Oxalidales order Rosales clade eurosids II family Tapisciaceae order Brassicales order Malvales order Sapindales clade asterids order Cornales order Ericales clade euasterids I family Boraginaceae family Icacinaceae family Oncothecaceae family Vahliaceae order Garryales order Gentianales order Lamiales order Solanales clade euasterids II family Bruniaceae family Columelliaceae family Eremosynaceae family Escalloniaceae family Paracryphiaceae family Polyosmaceae family Sphenostemonaceae family Tribelaceae order Apiales order Aquifoliales order Asterales order DipsacalesNote: "+..." = optionally separate family, that may be split off from the preceding family.
Note: This is a selected list of the more influential systems. There are many other systems, for instance a review of earlier systems, published by Lindley in his 1853 edition, Dahlgren. Examples include the works of Scopoli and Grisebach
The flowering plants known as angiosperms, Angiospermae or Magnoliophyta, are the most diverse group of land plants, with 64 orders, 416 families 13,164 known genera and c. 369,000 known species. Like gymnosperms, angiosperms are seed-producing plants. However, they are distinguished from gymnosperms by characteristics including flowers, endosperm within the seeds, the production of fruits that contain the seeds. Etymologically, angiosperm means a plant; the term comes from the Greek words sperma. The ancestors of flowering plants diverged from gymnosperms in the Triassic Period, 245 to 202 million years ago, the first flowering plants are known from 160 mya, they diversified extensively during the Early Cretaceous, became widespread by 120 mya, replaced conifers as the dominant trees from 100 to 60 mya. Angiosperms differ from other seed plants in several ways, described in the table below; these distinguishing characteristics taken together have made the angiosperms the most diverse and numerous land plants and the most commercially important group to humans.
Angiosperm stems are made up of seven layers. The amount and complexity of tissue-formation in flowering plants exceeds that of gymnosperms; the vascular bundles of the stem are arranged such that the phloem form concentric rings. In the dicotyledons, the bundles in the young stem are arranged in an open ring, separating a central pith from an outer cortex. In each bundle, separating the xylem and phloem, is a layer of meristem or active formative tissue known as cambium. By the formation of a layer of cambium between the bundles, a complete ring is formed, a regular periodical increase in thickness results from the development of xylem on the inside and phloem on the outside; the soft phloem becomes crushed, but the hard wood persists and forms the bulk of the stem and branches of the woody perennial. Owing to differences in the character of the elements produced at the beginning and end of the season, the wood is marked out in transverse section into concentric rings, one for each season of growth, called annual rings.
Among the monocotyledons, the bundles are more numerous in the young stem and are scattered through the ground tissue. They once formed the stem increases in diameter only in exceptional cases; the characteristic feature of angiosperms is the flower. Flowers show remarkable variation in form and elaboration, provide the most trustworthy external characteristics for establishing relationships among angiosperm species; the function of the flower is to ensure fertilization of the ovule and development of fruit containing seeds. The floral apparatus may arise terminally from the axil of a leaf; as in violets, a flower arises singly in the axil of an ordinary foliage-leaf. More the flower-bearing portion of the plant is distinguished from the foliage-bearing or vegetative portion, forms a more or less elaborate branch-system called an inflorescence. There are two kinds of reproductive cells produced by flowers. Microspores, which will divide to become pollen grains, are the "male" cells and are borne in the stamens.
The "female" cells called megaspores, which will divide to become the egg cell, are contained in the ovule and enclosed in the carpel. The flower may consist only of these parts, as in willow, where each flower comprises only a few stamens or two carpels. Other structures are present and serve to protect the sporophylls and to form an envelope attractive to pollinators; the individual members of these surrounding structures are known as petals. The outer series is green and leaf-like, functions to protect the rest of the flower the bud; the inner series is, in general, white or brightly colored, is more delicate in structure. It functions to attract bird pollinators. Attraction is effected by color and nectar, which may be secreted in some part of the flower; the characteristics that attract pollinators account for the popularity of flowers and flowering plants among humans. While the majority of flowers are perfect or hermaphrodite, flowering plants have developed numerous morphological and physiological mechanisms to reduce or prevent self-fertilization.
Heteromorphic flowers have short carpels and long stamens, or vice versa, so animal pollinators cannot transfer pollen to the pistil. Homomorphic flowers may employ a biochemical mechanism called self-incompatibility to discriminate between self and non-self pollen grains. In other species, the male and female parts are morphologically separated, developing on different flowers; the botanical term "Angiosperm", from the Ancient Greek αγγείον, angeíon and σπέρμα, was coined in the form Angiospermae by Paul Hermann in 1690, as the name of one of his primary divisions of the plant kingdom. This included flowering plants possessing seeds enclosed in capsules, distinguished from his Gymnospermae, or flowering plants with achenial or schizo-carpic fruits, the whole fruit or each of its pieces being here regarded as a seed and naked; the term and its antonym were maintained by Carl Linnaeus with the same sense, but with restricted application, in the names of the orders of his class Didynamia. Its use with any