Gymnospermae

Gymnospermae (Gymnospermae) are 1 plants, both Archegoniatae It is. Seed plant They have. ovule (different from Pteridophyta ), but Carpels Do not pack into ovary , and naked ovules, endosperm Female (i.e. Prothallus ) has been formed before fertilization (unlike angiosperms).
Gymnospermae

Gymnospermae A brief history of plants

Initial Gymnosperms About 345 million years ago to 395 million years. The Paleozoic Era devonian Experience. Carboniferous , permian The Quaternary, Mesozoic to cenozoic. From gymnosperms to twenty-first Century today, the history of climate after several major changes, the group also repeatedly succession, and the different evolution path of development.
Small trees, shrubs, rare Liana Stems; vascular bundle Row into ring out. Cambium , Secondary xylem All by a few Tracheid Composition, dilute with catheter. Leaves mostly needle bar, or scale form. Flowers unisexual, Stamen (Microstrobilus) loose or tight arrangement,. Male flowers (microstrobil), most to 2 (diluted 1) Anther ( Microsporangium ), sessile or petiolate, pollen (with air or gas microspore), for Anemophily (male, antheridial cell Gametophyte Can or cannot swim swimming); ovule ( Megasporangia Naked) to more than 1 students, most born well developed or undeveloped Megasporophyll (i.e. Cone scales And set, collar or bead seat), megasporophyll never formed a closed ovary No, stigma, group of bundles of health, do not form Female flowers Or, to the majority of minority was born Floral axis On the formation of female flowers ( Megaspore Ye Qiu), or megasporophyll rachides was born in the top, with 1 ovules. Ovules erect or pendulous, The beads are Spore layer, thin layer two, the top Micropyle Ovule development within the female. Gametophyte And the female gametophyte Egg cell After fertilization, embryo development, gametophyte development around the embryo into other parts endosperm The beads are developed, seed coat, the ovule It developed into seed; embryo with two or more cotyledons, the endosperm is abundant.
The occurrence and development of a long history of gymnosperms, the original gymnosperms appeared about 345 million years ago to 395 million years. The Paleozoic Era devonian And after the Paleozoic Carboniferous , permian The Mesozoic. The Triassic Period , Jurassic Period And cretaceous, Cenozoic era The The third century Quaternary. From gymnosperms to twenty-first Century today, geologic history After several major changes in climate, gymnosperms species with many species have evolved change, old extinction, new species have evolved species succession Reproduction So far, there are many types of modern gymnosperms is from about 2 million 500 thousand years ago to 65 million years of the new generation of third century appeared, and after quaternary glaciation During the period of preserved, since reproduction.
Modern species of gymnosperms belonging to 5 classes (Ginkgopsida, cycadopsida, taxopsida Pinopsida, Gnetales), 9 orders and 12 families 71 genera and nearly 800 species. 236 species and 47 varieties belonging to China has 5 classes and 8 orders and 11 families of.41, the introduction and cultivation of 1 families and 7 genera 51 species and 2 varieties.
In China many important timber species gymnosperm forestry operation, but also fiber and resin, Tannin A few kinds of materials such as tree leaves, pollen, seeds, root bark for medicinal.

Gymnospermae Morphological character

bare
 Keteleeria Keteleeria
Sub plant perennial woody plant, mostly Single axis The tall trees, small shrubs, lianas dilute; Secondary xylem By a few Tracheid Composition, dilute with catheter. Yedo linear, needle shaped or squama shaped, thin pinnatisect, fan-shaped, broad shape, strip or membranous sheath. Flowers unisexual, dioecious or monoecious; microstrobil ( Male flowers ) most Microstrobilus (Xiong Rui), Microstrobilus to 2 most Microsporangium ( Anther ), microspore (pollen) with balloon or boat shaped monocolpate, or spherical outer wall with a papillary projection or with obvious or not obvious Germination hole Or inaperturate, or an olive shape with multiple longitudinal ribs and grooves, sometimes also with a far pole ditch, for Anemophily After pollen germination, Pollen tube There are two swimming or swimming sperm; Megasporophyll ( Cone scales Collar, collar, sleeve, beads are not closed form) ovary A student, one or more pieces of bare ovule Most clusters form the trunk, top or in the shaft Megaspore (head Female flowers ); ovules erect or pendulous, by embryo sac , Nucellus and The beads are The top. Micropyle . Seeds exposed to Seed scales Above, or how much is abnormal megasporophyll development aril package, the embryo by the female Gametophyte The Egg cell Fertilized, endosperm From other parts of the female gametophyte development, seed coat by integument development and embryo with two or more; cotyledons. Chromosome number of gymnosperms less (x=8 ~ 20), the shape is bigger, in the basic agreement.

Gymnospermae ecological distribution

Gymnosperms are widely distributed in northern and southern hemisphere, especially in the northern hemisphere is more extensive, from low altitude to high altitude and high latitude from the low latitude almost all distribution. Gymnosperm families, genera and species is far less than angiosperms, but the forest coverage area is roughly equal. stay High latitude Area and high altitude climate cool to cold, almost all some gymnosperms formed or composed of three Mixed forest . The distribution of all kinds of gymnosperms as: Cycadaceae (Cycadaceae), Podocarpaceae (Podocarpaceae) and Araucariaceae (Araucariaceae), in addition to the type genus (i.e. Cycas , Podocarpus , Araucaria ) a few species of tropical and subtropical distribution in the northern hemisphere, other species are produced in the southern hemisphere; Ginkgo China is widely planted in native, subtropical and temperate regions of the northern hemisphere; Pinaceae (except Pinaceae) Pine (Pinus) a few species in the southern hemisphere, other species are produced in the northern hemisphere. Keteleeria , Pseudolarix , pseudotsuga , Cedrus , Cathaya Well, Pinus and Hemlock Part of the species distribution in the subtropical low mountain to Zhongshan area, with increasing latitude or altitude, being cold and warm cool wet minority Pine , Hemlock spruce and Larch , Picea and Abies Instead of tree species; Taxodiaceae In addition to the monotypic genus athrotaxis produced in Australia, other species are distributed in the Northern Hemisphere Subtropical area ; Cupressaceae Located in the northern hemisphere; Three Cephalotaxaceae Located in the South and East Asia Indochina Peninsula North; Taxaceae In addition to Australia Taxus yield New Caledonia Outside, other species are distributed in the northern hemisphere subtropical and temperate; Ephedra Located in the Northern Hemisphere temperate and subtropical mountain; Gnetaceae The tropical and subtropical regions distributed in Asia, Africa and South America; Single type section Welwitschiaceae In distribution Angola Tropical Africa and southeast.

Gymnospermae Evolution

Many scholars believe that the gymnosperm is composed of Progymnosperms (Progymnospermae) and Seed ferns (Pteridospermopsida, i.e. Brainea Cycadofilicopsida) evolved. Filicinae (Filicopsida) may originate from psilophytopsid and progymnosperms (Psilophyta), and seed ferns and other gymnosperms and parallel originated in the progymnosperms. Kodak class (Cordaitopsida) may originate from the progymnosperms, and The Cycads Class (Bennettitopsida, which intends to Cycas Cycadeoideopsida) may originate from seed ferns of the Savoy Fern Class (Lyginopteridatae), cycads (Gycadopsida) closely with curly fern phylogeny. Ginkgo (Ginkgopsida) and harsh to di class might have a common origin, they may be caused by Progymnosperms The evolution with a branch, or start independent evolution into two parallel branches. Conifers (Coniferopsida) has a close relationship with the severity of class to di. Cover plant (Chlamydospermopsida) is a very special group, because of the lack of palaeobotany data, there is no clarification of the origin and evolution of the report.

Gymnospermae Classification status

In gymnosperms The earth's environment When a large number of big change has now extinct, surviving only eight hundred kinds, which accounted for more than and 300 China. In gymnosperms Higher plant Often as a Natural group The. Classification unit For the door, or subdivisions of classes, including the extinct species, such as Seed ferns And the opening (Cayoniopsida), glossopteris (Giossopteridopsida), five wooden columns (Pentaxyopsida), The Cycads Kodak, etc., and the survival of the modern taxa (e.g. Cycas Ginkgo, pine, fir, plant cover etc.). In gymnosperm classification systems (such as R G Chamberlain rocked 1926, 1935, D - A - A - Johannsen 1951, Herta 1953, Jiang tower successfully, R rocked and H Mel Xiao 1954, W Zimmerman 1959, Wan Chun Cheng 1978), the following differences of opinion on the existing various gymnosperms: 1 in Ginkgo biloba Cycadopsida In parallel or in cycads, Coniferopsida In parallel with conifers, cycads, ginkgo, pine or fir are tied for the class. This is a comparative study on the structure and reproductive organs of Ginkgo vegetative development, different conclusions emphasize that different characters. 2 Taxaceae A fir class or an independent class, and cycads, ginkgo, pine and fir Cover plant Parallel. This is a single terminal of Taxus ovule Two radically different views for different interpretations of. The fir class (mesh) contained according to whether subjects Female flowers formation cone Or not to two Subclass (or suborder).

Gymnospermae The scope of application

In addition to a small number of taxa (such as gymnosperms gnetum and Pinaceae Some of the genera), have double Flavonoids There is a common. Amentoflavone And sciadopitysin, Bilobetin And yellow pigment, Torreya flavin etc.. Flavonoids are ubiquitous, there is a common quercrtin, Kaempferol and The bark of Myrica rubra Et. Only in the alkaloid Three Cephalotaxaceae , Ephedra And the Gnetaceae in existence, can be used for medicine. Cycadaceae , Taxaceae and Podocarpaceae Some species of ornamental and other many kinds of tall trees, the straight trunk, The material rate High, the material is excellent, for construction, furniture and industrial materials, accounting for more than 50% of the world supply of wood; some species can be cut from rosin and turpentine; a few species of edible seeds; some species of fast-growing tree species or landscape trees; the upper reaches of the river for water conservation forest in the alpine slopes was born; can prevent the rain erosion.