| Magnoliids | |
|---|---|
 | |
| Flower ofAsimina triloba | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Magnoliids |
| Type species | |
| Magnolia virginiana | |
| Orders | |
Magnoliids,Magnoliidae orMagnolianae are a clade offlowering plants. With more than 10,000 species, includingmagnolias,nutmeg,bay laurel,cinnamon,avocado,black pepper,tulip tree and many others, it is the third-largest group of angiosperms after theeudicots andmonocots.[3] The group is characterized bytrimerous flowers,pollen with one pore, and usually branching-veined leaves.
Some members of the subclass are among the earliest angiosperms and share anatomical similarities withgymnosperms likestamens that resemble the male cone scales ofconifers andcarpels found on the long flowering axis.[4] According tomolecular clock calculations, the lineage that led to magnoliids split from other plants about 135million years ago[5] or 160-165 million years ago.[6]
"Magnoliidae" is thebotanical name of asubclass, and "magnoliids" is an informal name that does not conform to theInternational Code of Nomenclature for algae, fungi, and plants. Thecircumscription of a subclass will vary with thetaxonomic system being used. The only requirement is that it must include the familyMagnoliaceae.[7] The informal name "magnoliids" is used by some researchers to avoid the confusion that recently surrounds the name "Magnoliidae." More recently,[clarification needed] the group[clarification needed] has been redefined under thePhyloCode as a node-basedclade comprising theCanellales,Laurales,Magnoliales, andPiperales.[citation needed] Chase & Reveal have proposed "Magnoliidae" as the name used for the entire group of flowering plants, and the formal name "Magnolianae" for the group of four orders discussed here.[8]
TheAPG III (2009) and its predecessor systems did not originally use formal botanical names above therank of order. Under those systems, larger clades were usually referred to by informal names, such as "magnoliids" (plural, not capitalized) or "magnoliid complex". The formal name inLinnean nomenclature was specified in a separate APG publication as the existing name "Magnolianae"Takht. (1967).[8] The APG III recognizes aclade within theangiosperms for the magnoliids. The circumscription is:
clademagnoliids
| |
| The currentphylogeny and composition of the magnoliids.[9][10] | |
The clade includes most of the basal groups of the angiosperms. This clade was formally named Magnoliidae in 2007 under provisions of thePhyloCode.[11]
TheCronquist system (1981) used the name Magnoliidae for one of six subclasses (within classMagnoliopsida =dicotyledons). In the original version of this system the circumscription was:[12]
BothDahlgren andThorne classified the magnoliids (sensu APG) in superorderMagnolianae, rather than as a subclass.[13] In their systems, the name Magnoliidae is used for a much larger group including alldicotyledons. This is also the case in some of the systems derived from the Cronquist system.[citation needed]
Dahlgren divided his Magnolianae into tenorders, more than other systems of the time, and unlike Cronquist and Thorne, he did not include thePiperales.[14] Thorne grouped most of his Magnolianae into two large orders,Magnoliales andBerberidales, although his Magnoliales was divided into suborders along lines similar to the ordinal groupings used by both Cronquist and Dahlgren. Thorne revised his system in 2000, restricting the name Magnoliidae to include only the Magnolianae, Nymphaeanae, and Rafflesianae, and removing the Berberidales and other previously included groups to his subclass Ranunculidae.[15] This revised system diverges from the Cronquist system, but agrees more closely with the circumscription later published under APG II.[citation needed]
Comparison of classification systems is often difficult. Two authors may apply the same name to groups with different composition of members; for example, Dahlgren's Magnoliidae includes alldicots, whereas Cronquists' Magnoliidae is only one of five dicot groups. Two authors may also describe the same group with nearly identical composition, but each may then apply a different name to that group or place the group at a differenttaxonomic rank. For example, the composition of Cronquist'ssubclass Magnoliidae is nearly the same as Thorne's (1992)superorder Magnolianae, despite the difference in taxonomic rank.[citation needed]
Because of these difficulties and others, the synoptic table below imprecisely compares the definition of "magnoliid" groups in the systems of four authors. For each system, only orders are named in the table. All orders included by a particular author are listed and linked in that column. When a taxon is not included by that author, but was included by an author in another column, that item appears in unlinked italics and indicates remote placement. The sequence of each system has been altered from its publication in order to pair corresponding taxa between columns.
| APG II system (2003)[16] magnoliids | Cronquist system[12] Magnoliidae | Dahlgren system[14] Magnolianae | Thorne system (1992)[13] Magnolianae | Thorne system (2000)[15] Magnolianae |
|---|---|---|---|---|
| Laurales | Laurales | Laurales | Magnoliales | Magnoliales |
| Magnoliales | Magnoliales | Magnoliales | ||
| Annonales | ||||
| Canellales | Winterales | |||
| Piperales | Lactoridales | |||
| Aristolochiales | Aristolochiales | |||
| Piperales | Piperales in Nymphaeanae | |||
| unplaced or in basal clades | Chloranthales | |||
| Illiciales | Illiciales | |||
| in Rosidae | Rafflesiales | in Rafflesianae | in Rafflesianae | |
| Nymphaeales | in Nymphaeanae | in Nymphaeanae | in Nymphaeanae | |
| Ceratophyllales | in Ranunculidae | |||
| placed in eudicot clade | Nelumbonales | Nelumbonales | ||
| Ranunculales | in Ranunculanae | Berberidales | ||
| Papaverales | ||||
| in Dilleniidae | in Theanae | Paeoniales |
The magnoliids is a large group of plants, with many species that are economically important as food, drugs, perfumes, timber, and as ornamentals, among many other uses.
One widely cultivated magnoliidfruit is theavocado (Persea americana), which is believed to have been cultivated inMexico andCentral America for nearly 10,000 years.[17] Now grown throughout the tropics, it probably originates from theChiapas region of Mexico orGuatemala, where "wild" avocados may still be found.[18] The soft pulp of the fruit is eaten fresh or mashed intoguacamole. The ancient peoples of Central America were also the first to cultivate several fruit-bearing species ofAnnona.[12] These include thecustard-apple (A. reticulata),soursop (A. muricata), sweetsop orsugar-apple (A. squamosa), and thecherimoya (A. cherimola). Both soursop and sweetsop now are widely grown for their fruits in the Old World as well.[19]
Some members of the magnoliids have served as important food additives, such asblack pepper,nutmeg,bay laurel andcinnamon. Oil ofsassafras was formerly used as a key flavoring in bothroot beer and insarsaparilla.[20] The primary ingredient responsible for the oil's flavor issafrole, but it is no longer used in either theUnited States orCanada. Both nations banned the use of safrole as a food additive in 1960 as a result of studies that demonstrated safrole promotedliver damage andtumors in mice.[21] Consumption of more than a minute quantity of the oil causesnausea, vomiting, hallucinations, and shallow rapid breathing. It is very toxic, and can severely damage the kidneys.[22] In addition to its former use as a food additive, safrole from eitherSassafras orOcotea cymbarum is also the primary precursor for synthesis of MDMA (methylenedioxymethamphetamine), commonly known as the drug ecstasy.[23]
Other magnoliids also are known for their narcotic, hallucinogenic, or paralytic properties. ThePolynesian beveragekava is prepared from the pulverized roots ofPiper methysticum, and has both sedative andnarcotic properties.[19] It is used throughout the Pacific in social gatherings or after work to relax. Likewise, some native peoples of theAmazon take ahallucinogenicsnuff made from the dried and powdered fluid exuded from the bark ofVirola trees.[12] Another hallucinogenic compound,myristicin, comes from the spice nutmeg.[24] As with safrole, ingestion of nutmeg in quantities can lead to hallucinations, nausea, and vomiting, with symptoms lasting several days.[25] A more severe reaction comes from poisoning byrodiasine anddemethylrodiasine, the active ingredients in fruit extract fromChlorocardium venenosum. These chemicals paralyze muscles and nerves, resulting intetanus-like reactions in animals. TheCofán peoples of westernmost Amazon inColombia andEcuador use the compound as a poison to tip their arrows in hunting.[26]
Not all the effects of chemical compounds in the magnoliids are detrimental. In previous centuries, sailors would use Winter's Bark from theSouth American treeDrimys winteri to ward off the vitamin-deficiency ofscurvy.[19] Today,benzoyl is extracted fromLindera benzoin (common spicebush) for use as a food additive and skin medicine, due to its anti-bacterial and anti-fungal properties.[27] Drugs extracted from the bark ofMagnolia have long been used in traditional Chinese medicine. Scientific investigation ofmagnolol andhonokiol have shown promise for their use in dental health. Both compounds demonstrate effective anti-bacterial activity against the bacteria responsible forbad breath anddental caries.[28][29] Several members of the familyAnnonaceae are also under investigation for uses of a group of chemicals calledacetogenins. The first acetogenin discovered wasuvaricin, which has anti-leukemic properties when used in living organisms. Other acetogenins have been discovered with anti-malarial and anti-tumor properties, and some even inhibitHIV replication in laboratory studies.[30]
Many magnoliid species produceessential oils in their leaves, bark, or wood. The treeVirola surinamensis (Brazilian "nutmeg") containstrimyristin, which is extracted in the form of a fat and used insoaps andcandles, as well as inshortenings.[31] Other fragrant volatile oils are extracted fromAniba rosaeodora (bois-de-rose oil),Cinnamomum porrectum,Cinnamomum cassia, andLitsea odorifera for scenting soaps.[32]Perfumes also are made from some of these oils;ylang-ylang comes from the flowers ofCananga odorata, and is used byArab andSwahili women.[19] A compound callednutmeg butter is produced from the same tree as the spice of that name, but the sweet-smelling "butter" is used in perfumery or as alubricant rather than as a food.[citation needed]
