词条 | Magnoliales |
释义 | Magnoliales plant order Introduction ![]() Distribution and abundance ![]() ![]() ![]() ![]() ![]() Eupomatiaceae consists of one genus, Eupomatia, with two species. Eupomatia laurina is a common rainforest shrub in New Guinea and Australia, from southern Australia along the eastern coast as far north as tropical Queensland. The other species, Eupomatia bennettii, is much less common and is restricted to Australia, where it occurs near the coastal regions of northern New South Wales and Queensland. Himantandraceae contains one genus, Galbulimima (also known as Himantandra), found in the Molucca Islands (Moluccas) of Indonesia, Malaysia, New Guinea, and northeastern Australia. Economic and ecological importance Annonaceae Timber Because the family Annonaceae is by far the largest in the Magnoliales order, it is not surprising that this group includes the most species that yield some type of economic product. The wood of many members of Annonaceae is very pliable, and many of the edible fruits have commercial value. Oxandra lanceolata ( lancewood), from northern South America and the West Indies, is undoubtedly the most important commercial timber source in this family. The wood is yellow to olive-yellow, hard, heavy, and of fine texture, and it has a very straight grain. These characteristics make the wood suitable for use in scientific instruments, turnery (objects shaped by lathe), tool handles, and such sporting goods as archery bows and fishing rods. Guatteria boyacana (solera, or Colombian lancewood) has most of the same properties and uses, though it is not as well known in the timber trade. Enantia chlorantha (African whitewood), a yellowwood from Liberia, Ivory Coast, and Cameroon, produces a sulfurous yellow dye; the wood also is used locally to make unpainted furniture and veneers. Cleistopholis patens (otu) yields a soft, light wood from western Africa that finds some of the same uses as balsa wood—e.g., in buoys, life rafts, and floats. The fibrous inner bark is of some value for cordage and coarse netting. In South America, balsalike wood is obtained from Heteropetalum brasiliense, which grows along “blackwater” streams (swampy rivers stained dark by organic acids) in the upper Orinoco (Orinoco River) and Río Negro basins of Amazonia. Polyalthia longifolia is a tall, handsome tree with pendent linear leaves that is cultivated in most parts of Sri Lanka and India as an avenue tree and around temples for its religious significance. Although the wood is not very durable, it is utilized to some extent in making matches, boxes, and packing crates. Other woods of the Annonaceae family in India and Myanmar that have some commercial value are derived from the genera Miliusa, Sageraea, Mitrephora, Saccopetalum, and Cyathocalyx. Because of their tough and elastic qualities, these woods are utilized in the manufacture of tool handles, wheel spokes, and sporting goods. Certain Asiatic species of Polyalthia (P. cerasoides and P. korinti), Uvaria (U. burahol, U. dulcis, and U. heterophylla), and Artabotrys produce edible fruit, as do African species of Uvaria (U. chamae and U. globosa). The wood of Xylopia aethiopica is quite flexible and has some local use in west-central Africa for masts, boat paddles, and rudders. It has been described as termite-proof and, accordingly, is used for house posts and beams. The dried black fruits of this species are called guinea peppers and were once of commercial importance in Europe as a tangy condiment and drug. Fruit ![]() Annona squamosa ( sweetsop, or sugar apple), although native to northern South America, Central America, and the Caribbean region, is even more widely cultivated and highly esteemed in India and Pakistan. The conical fruits break into segments when ripe and expose a cream-coloured sweet pulp in which dark brown glossy seeds are embedded. Among the natives of the tropics, the sugar apple tree is reputed to be of medical value. Tea made from the roots is highly purgative, while that made from the leaves is a mild laxative and is also considered to have a general tonic effect on the digestive tract. Poultices of the leaves are used in dressing infected wounds. The cherimoya is the fruit of a rather small tree, Annona cherimola, which is native to the cool (but frost-free) mountain valleys of Peru and Ecuador. Although it is grown in southern Florida, it does not produce fruit well there because of the high humidity; it is currently commercially grown on a small scale in southern California. The fruits, however, are quite perishable and ferment readily. Like the sugar apple, it is now established in the Old World tropics. Although the fruit does not break into segments when ripe the way that the sugar apple does, the flesh is of a more creamy consistency (it contains up to 18 percent sugar) and has fewer seeds. Under ideal conditions, the fruit may attain a large size, weighing up to 7 kg (16 pounds). ![]() Other species of Annona that produce comparatively inferior fruit but are eaten locally include A. montana (mountain soursop), from the West Indies and South America; A. longiflora, from Mexico; A. paludosa, from Brazil; A. testudinea, from Honduras; A. nutans, from Paraguay; A. senegalensis, from East and West Africa; and A. diversifolia (ilama), which was first cultivated long ago by the Aztecs (Aztec) of Mexico. Two species of Rollinia (R. mucosa and R. pulchrinervis) have edible fruits that reach 10 cm (4 inches) in length and bear some resemblance to those of the soursop, except that the spines are softer and more blunt. Rollinia mucosa is a large tree native to the West Indies and northern South America, whereas R. pulchrinervis is native to the Amazon River basin. Both species are referred to by the common name biriba, and both are widely cultivated, particularly throughout Brazil, for their delicious fruits. ![]() Chemicals ![]() In the upper Amazon region, Indian tribes use an extract from the tree Unonopsis veneficiorum to tip their poison blowgun darts and arrows; this substance has a similar paralyzing effect on humans and other animals to that caused by curare, which is obtained from the genus Strychnos of the family Loganiaceae. Myristicaceae Although many trees in Myristicaceae, or the nutmeg family, reach timber size, the wood is not of much value in world trade. Nevertheless, Dialyanthera otoba (otobo), Iryanthera sagotiana (marakaipo), and Virola koschnyi (banak) from tropical regions of South and Central America, Pycnanthus kombo and Staudtia gabonensis from West African countries, and Myristica irya (chuglum) from the Andaman Islands in the Bay of Bengal find local use in the manufacture of furniture, millwork, flooring, and general carpentry. ![]() Myristica fragrans is a handsome evergreen with dark leaves that reaches a height of 9 to 18 metres (30 to 60 feet). The small, yellow, fleshy flowers are unisexual, and the plants producing them are dioecious—i.e., the male and female flowers are produced on separate trees. The ripe fruits are golden-yellow and resemble apricots (apricot) or pears (pear). As the fruits dry out, they split open, revealing a single shiny brown seed covered with a bright red fleshy structure called an aril. Inside the seeds are the kernels, which are the nutmegs of commerce; the aril is the source of mace. The pulverized seed finds much use for seasoning such food items as spiced fruits, sausages, pastries, puddings, and eggnog. Mace is one of the most delicately flavoured spices and is used in making baked goods, pickles, ketchups, and sauces. Nutmeg and mace contain myristicin, a substance poisonous in large amounts. Myristicin is described by some as a hallucinogen. Nutmeg butter is derived from the seeds and is used in ointments and in candles. Magnoliaceae ![]() ![]() Many of the cultivated magnolias are hybrids. Probably the most widely cultivated of these is Magnolia × soulangeana (saucer magnolia), a spreading deciduous shrub with leaves that measure up to 15–20 cm (6–8 inches) long. Its flowers appear in early spring before the leaves, and this flowering continues after the leaves have developed. The flowers are typically white at their tips, with dark pink staining the bases of the perianth. This hybrid was formed in 1820 by crossing M. denudata with M. liliflora. The cross took place by chance in the garden of a château belonging to Étienne Soulange-Bodin, founder of the National Horticultural Society of France. The stock soon flowered and was purchased by a British nursery that paid 500 guineas for it, a considerable sum in those days. The hybrid is tolerant of most soils and atmospheric pollution. There are now many forms of this hybrid, with flowers ranging from completely white to claret-purple. Another well-known hybrid is Magnolia × veitchii, which was formed by crossing M. campbellii with M. denudata. ![]() Degeneria and Himantandraceae Both species of Degeneria (D. vitiensis and D. roseiflora) have been milled for timber, which has been used in building construction and for furniture and veneer. They are too scattered, however, to be deliberately sought for timber. Wood from Galbulimima (family Himantandraceae) has been used in Australia for cabinetmaking. The leaves and bark contain piperidine derivatives, which have narcotic and hallucinogenic effects. In Papua New Guinea, Galbulimima is used in combination with the leaves of Homalomena (family Araceae), which causes violent intoxication followed by sleep with visions and dreams. The wood of Eupomatia laurina is used for furniture making in regions where it grows. Characteristic morphological features Magnoliales are woody plants with simple (seldom lobed) leaves and ethereal oil cells in the parenchymatous tissues of the plant body. The ovary is usually placed above the base of the stamens in the flower (hypogynous), and the perianth is well developed. The pollen is typically uniaperturate (sometimes biaperturate or inaperturate), and the seeds have a small embryo and abundant endosperm. Many unspecialized features of the angiosperms (angiosperm) can be found in Magnoliales. Annonaceae In Annonaceae, the alternate leaves are without stipules and frequently have a characteristic metallic sheen. The fragrant, often pendulous flowers frequently open before all the parts are mature. Flower parts are mostly in threes. Stamens usually have a short, stout filament and a connective that is expanded above the pollen sacs. Pollen is more varied than in any other family of Magnoliales. The fruits are usually berries, which may, as in Annona (custard apples), be fused to form aggregate fruits. Myristicaceae Myristicaceae species have unisexual flowers that are usually situated on separate plants. Many trees have a distinctive growth pattern with whorled, almost horizontal, branches. The fruits of nutmeg, the best-known member of the family, are described in the section Economic and ecological importance (Magnoliales). Magnoliaceae ![]() Degeneriaceae The two species in Degeneriaceae (Degeneria vitiensis and D. roseiflora) are large trees and have primitive vessels, single pollen grains with an elongated aperture and a homogenous (structureless) exine, and sterile stamens (staminodes) between the fertile stamens and the central single carpel. The unusual kidney-shaped fruits of Degeneria measure up to 12 cm (almost 5 inches) long; they split open along one side to reveal orange or red seeds embedded in a pulp. The seeds hang down from the open fruit and are dispersed by birds. The embryos have three or four cotyledons (cotyledon), a most unusual feature. Eupomatiaceae Members of Eupomatiaceae are shrubs to small trees. Eupomatia laurina reaches heights of up to 5 metres (16 feet). At the other end of the scale, E. bennettii rarely exceeds 50 cm (20 inches). It often has only one leafy shoot, which produces a single flower each year. The flowers lack a perianth but have petal-like staminodes between the stamens and carpels. The stamens are short with broad flat bases; the carpels are fused along the sides and are enclosed by a cup-shaped receptacle, so that only their receptive stigmatic apexes are exposed to the beetles that pollinate them. The carpels are a modified conduplicate type without a style. The pollen of both species is subspheroidal with a bandlike encircling aperture around the middle of the grain. Each fruit is a globose berry consisting of the fused spirally arranged carpels. Himantandraceae Himantandraceae consists of a single genus of large trees, Galbulimima (also known as Himantandra). The vessels of the mature wood have simple perforations (a more advanced feature than in Degeneria). The alternate leaves have their lower surfaces covered with characteristic shield-shaped hairs. Flowers are usually solitary, as in Degeneria, and have two unusual leathery sepals that fall off when the flower opens. There are about 7 to 9 petals; the stamens resemble the petals in shape and texture, and the 4 pollen sacs are restricted to the lowermost part of the stamen, an unusual feature. The 6–10 spirally arranged carpels, with 1 (or, rarely, 2) ovule, fuse to form a globe-shaped, fleshy fruit. Evolution Many botanists used to regard Magnoliales as the most primitive extant angiosperm order. A number of structural features were used to support this hypothesis: flowers with numerous spirally arranged free parts on an elongated floral axis; frequently broad stamens (male), with pollen sacs embedded in their surfaces; carpels (female) that may be only slightly modified from a leaflike structure; pollen grains that usually have a single germination groove; and seeds containing a small embryo surrounded by abundant, food-rich endosperm. Molecular evidence, however, has placed other groups as more basal in the angiosperm tree, but the order is nonetheless considered basal among the flowering plants. Additional Reading Coverage is provided by F.B. Sampson, J.B. Williams, and Poh S. Woodland, “The Morphology and Taxonomic Position of Tasmannia glaucifolia (Winteraceae), a New Australian Species,” Australian Journal of Botany, 36(4):395–414 (1988), a rather specialized discussion of the reasons for keeping Drimys and Tasmannia as separate genera in the Winteraceae and a description of a new and unusual species of this most primitive of extant families; J.M. Miller, “The Archaic Flowering Plant Family Degeneriaceae: Its Bearing on an Old Enigma,” National Geographic Research, 5(2):218–231 (1989), a fascinating and readable account of Degeneria, including the discovery of a new species by the author, with excellent colour illustrations; and James M. Gardiner, Magnolias (1989). |
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