Spermatophyta is the highest class of plants in the plant kingdom.Because their vascular tissues are more complex, their ability to transport water and nutrients is improved, their sporophytes are further developed and their gametophytes are more simplified.The gametophyte is completely parasitic in the sporophyte.Because of the appearance of pollen tube, sexual process completely gets rid of water environment, which is a great progress for seed plants to adapt to terrestrial life.In addition, because of the seeds, it is more advantageous in reproduction, and improves the ability to resist and adapt to adverse environments, thus providing a better guarantee for the growth of a generation.[1]
The spermatophyta can be divided intoGymnosperma(Gymnospermae) andAngiosperma（ Argiopemae）。[1]
The spermatophyta is divided intoAngiospermaandGymnosperma。Now the phylum of spermatophyta has been withdrawn, and the spermatophytes are divided intoAngiospermaandGymnosperma。
Reproductive organThe type and structure of are also complex.reproductionForming a ball orFLOWER, cones or fruits, andseed。They have stable and significant characteristics, and are an important basis for classification.The gametophyte is very small and appears only at flowering, parasitic on the sporophyte.The fertilized egg absorbs the nutrients from the endosperm to form an embryo, and then develops into a seed. After the seed matures, it separates from the original plant body, so it is more suitable forlandGrowth.seed plantOfovule(equivalent to the megasporangia of ferns)GymnospermsThe ovule enclosed in the ovary wall is called angiosperm.
seedBotanyByancientalong withFernPlants evolved.TheirreproductionOrgans and forms are closely related, but the terms used are different.
Gymnosperma
Announce
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Gymnospermae，Gymnosperms are primitive seed plants.
morphological character
Trees, rarely shrubs, rarely woody vines.Female cones have ovules, and the scales of the attached ovules areMegasporium(nucellar scale, integument, nucellus), which does not form a closed ovary, so the ovule is exposed, so it is called gymnosperm.This is a significant difference between gymnosperms and angiosperms.The ovule has a integument with a micropyle at the top. The ovule develops into a gametophyte. The egg cell of the female gametophyte develops into an embryo after sperm. The other parts of the gametophyte develop into endosperm, the integument develops into a seed coat, and the whole ovule develops into a seed.This is the main difference between gymnosperms and ferns.Its leaves are mostly needle shaped, linear or scale shaped, also known as conifers.The vascular bundles of the stem are arranged in a ring, with cambium,Secondary xylemIt is almost composed of tracheids, with few vessels;The phloem has no companion cell.Cotyledons 1 to many.Gymnosperms are older than angiosperms and are mostly fossil plants. Many existing gymnosperms are of Cenozoic era.[2]
Reproductive mode
coneMonoecious。The megaspore is the first cell of the female gametophyte.There are usually four megaspores in the ovule, but the upper three degenerate and disappear, and only the lowest one develops into a female gametophyte.The microspore is the first cell of the male gametophyte.The microspore has two walls, in which the spores are shaded.The mature pollen grain is a male gametophyte with four cells: two are degenerated prothallus cells, one is pollen tube cells, and the other is germ cells.During pollination, the pearl scales of the erect female cone are separated from each other and bear pollen. The ovule secretes liquid at the same time, which overflows from the micropyle and becomes a pollination drop. The pollen grains fall on it. This liquid is volatilized and lost, and the pollen grains fall into the micropyle.Thereafter, the pearl scales are closed, the female cones are pendulous, and the pollen grains give birth to pollen tubes, which pass through the nucellar tissue and reach the archegonium.Pollen tube is obviously used to transport sperm.The germ cell divides into two parts in the tube, the big one is the somatic cell, and the smaller one becomes a stalk behind it, called the stalk cell.Before fertilization, the somatic cell divides into two spermatids.There is a small amount of cytoplasm around the nucleus, so the sperm is still a cell, but it cannot swim without flagella.The wall of the somatic cell disappeared afterwards, and the two sperms were sent to the tip of the pollen tube.At this time, the neck cell of the archegonium degenerates, the pollen tube reaches the egg, the tip breaks, and two sperm are shot into the egg, one of which is fused with the egg.[3]
Time of occurrence
Tertiary period (about 2.5 million years ago to 65 million years ago), such as Ginkgo biloba, Keteleeria fortunei, Tsuga tsuga, Cunninghamia lanceolata, Metasequoia glyptostroboides, Torreya grandis, Taxus chinensis, etcrelict plant 。[2]Gymnosperms first appeared in the paleozoic era, most prosperous in the mesozoic era, and then gradually declined due to changes in geological history.[2]
Species distribution
There are nearly 800 existing gymnosperms belonging to 71 genera of 12 families, which are widely distributed all over the world, mainly in the Northern Hemisphere;There are 11 families, 41 genera and nearly 300 species (including those introduced and cultivated) in China.[2]
There are about 800 species, belonging to 5 classes: Cycadopsida, Ginkgopsida, Coniferopsida, Taxopsida, and Gnetopsida, belonging to 9 orders, 12 families, and 71 genera.Many gymnosperms are important trees.
Key values
Most of them are important timber trees in forestry production, or used for fiber, tannin, rosin, medicine, etc., with high economic value.[2]
Representative species
ginkgoGinkgobilobaL.
ginkgo
Arbor, up to 40 meters high, DBH up to 4 meters;The bark of young trees is light longitudinal split, and the bark of big trees is grayish brown, deep longitudinal split, rough;The young and adult tree crowns are conical, while the old ones are broadly oval;The branches are nearly whorled and extend obliquely upwards (the big branches of female plants are often more developed than those of male plants);The annual long branches are light brown yellow, and the biennial ones become gray with thin longitudinal cracks;The short branches are densely covered with leaf scars and are dark gray. Long branches can also grow on the short branches;Winter buds are yellowish brown, often ovoid, with a blunt tip.The leaves are fan-shaped, long stalked, light green, hairless, with many forked parallel veinlets, 5-8 cm wide at the top, often with wavy notches on short branches, often 2-lobed on long branches, wide cuneate at the base, 3-10 (mostly 5-8) cm long stalks, and the leaves on young trees and sprouting branches are often relatively deep lobed (13 cm long and 15 cm wide leaves),Sometimes the lobes divide again (this is similar to the leaves of more primitive fossil species). The leaves are scattered spirally on the annual growth branches, 3-8 leaves are clustered on the short branches, and turn yellow before falling leaves in autumn. The cones are dioecious, unisexual, and grow in clusters in the axils of the scaly leaves at the top of the short branches;Male cones are catkin shaped, pendulous, stamens loosely arranged, with short stalks, anthers often 2, long elliptic, anther chamber is longitudinally divided, and connectives do not appear;Female cones have long stems. The ends of the stems are often divided into two branches, 3-5 branches or no branches. Each branch ends with a dish shaped ovule base, on which the ovule is attached. Usually only the ovule at one fork end develops into a seed, which is pollinated by internal media.The seeds are long stemmed, pendulous, often elliptic, long obovate, ovoid or nearly spherical, 2.5-3.5 cm long, 2 cm in diameter, fleshy exotesta, yellow or orange when ripe, covered with white powder and smelly leaves;The middle part is white in skin and bone, with 2-3 longitudinal ridges;Endoderm membranous, reddish brown;The endosperm is fleshy and tastes sweet and bitter;There are 2 cotyledons, 3 rare ones, which are not unearthed during germination. There are 2-5 primary leaves, which are strip wide, about 5 mm long and 2 mm wide. The apex is slightly concave. The fourth or fifth subsequent leaves are fan shaped, with a deep crack and irregular wavy notch at the apex, and the petiole is 0.9-2.5 cm long;There is a primary root.The flowering period is from March to April, and the seeds mature from September to October.[4]
Ginkgo biloba is a rare relic tree species of the Mesozoic era, and is a native product of China. Only the Tianmu Mountain in Zhejiang Province has wild trees. It is born in natural forests in areas with an altitude of 500-1000 meters, acidic (pH 5-5.5) yellow soil, and good drainage. It is often mixed with coniferous and broad-leaved trees such as Cryptomeria fortunei, Cephalotaxus grandis, and Blueberry, and grows vigorously.Ginkgo biloba is cultivated in a wide range of areas: from Shenyang in the northeast to Guangzhou in the south, from 40-1000 meters above sea level in the east to Guizhou in the southwest, and below 2000 meters above sea level in the west of Yunnan (Tengchong), for the purpose of seed production or as a garden tree species.In the cultivation area, seedling, stem moving seedling or root tiller seedling are often used for grafting, which can blossom and bear fruit in 8-10 years in advance (seedling generally starts to bear seeds after 20 years).Ginkgo biloba cultivated in various places has hundreds or thousands of years old trees.It is cultivated in gardens in Korea, Japan, Europe and the United States.[4]
Ginkgo biloba is a light loving tree species with deep roots and wide adaptability to climate and soil. It can grow in areas with high temperature and rainfall, little rainfall and cold winter, but its growth is slow or poor;It can grow on acid soil (pH 4.5), calcareous soil (pH 8) and neutral soil, but it is not resistant to saline alkali soil and too wet soil.The best growing areas in areas with deep soil layer, fertile and humid soil and good drainage, where the climate is warm and humid below 1000 meters above sea level (1500-2000 meters in Yunnan) and the annual precipitation is 700-1500 mm, coexist peacefully in areas where the soil is thin and dry, and rocky hillsides are excessively humid, and do not survive late or grow poorly.[4]
Ginkgo biloba is a fast-growing precious timber tree species. The sapwood is light yellow, the heartwood is light yellowish brown, thin in structure, light soft, elastic, easy to process, shiny, with a specific gravity of 0.45-0.48. It is not easy to crack and flex. It is an excellent timber for buildings, furniture, interior decoration, sculpture, drawing boards, etc.The seeds are used for food and medicine.The leaves can be used as medicine, insecticide and fertilizer.The fleshy testa of the seed contains leucolic acid, ginkgo alcohol and ginkgo phenol, which are toxic.The bark contains tannin.The ginkgo tree has a beautiful shape, with green leaves in spring and summer and yellow leaves in autumn. It can be used as garden trees and street trees.[4]
CycasCycasrevolutaThunb.
Cycas
The tree trunk is about 2 meters high, up to 8 meters or more. If there are obvious diamond petiole scars in spiral arrangement, it is cylindrical.The pinnate leaves grow from the top of the stem, the lower layer bends downward, and the upper layer extends obliquely upward. The entire contour of the pinnate leaves is inverted oval narrow lanceolate, 75-200 cm long. The leaf axis is square and round in cross section, the handle is slightly quadrangular, and there are toothed spines on both sides, which extend horizontally or slightly obliquely upward, and the spines are 2-3 mm long;More than 100 pairs of pinnate lobes, linear, thick leathery, hard, 9-18 cm long, 4-6 mm wide,Diagonal upward to form "V""Shape, the edge is significantly rolled down, the upper part is slightly narrower, the apex has a spiny tip, the base is narrow, the two sides are asymmetric, the lower side is extended downward, the upper side is dark green and shiny, the center is slightly concave, there is a slightly raised midvein in the groove, the lower side is light green, the midvein is significantly raised, and there are sparse hairs or no hairs on both sides. Male cones are cylindrical, 30-70cm long, 8-15cm in diameter, with short stems, small sporesThe cotyledons are narrow cuneate, 3.5-6 cm long, and flat at the top. Their two corners are nearly circular, 1.7-2.5 cm wide, and have sharp tips. The tips are about 5 mm long, upright, and gradually narrow at the lower part. The upper part is nearly keel shaped, and the lower middle rib and the top are densely covered with yellowish brown or grayish yellow long hairs. 'The anthers are usually three;MegasporiumIt is 14-22cm long and densely covered with yellowish or grayish yellow hairs. The top of the upper part is ovate to long ovate, and the edge is pinnately divided. There are 12-18 pairs of lobes, which are strip shaped and subulate. It is 2.5-6cm long. The apex has a spiny tip, and 2-6 ovules are born on both sides of the megaspore petiole, with hairs.The seeds are reddish brown or orange red, obovoid or ovoid, slightly flat, 2-4cm long, 1.5-3cm in diameter, densely covered with grayish yellow short villi, gradually falling off later, the mesotesta is woody, with two ridges on both sides, no ridge on the upper end or inconspicuous ridge, and a sharp head on the top.The flowering period is from June to July, and the seeds mature in October.[5]
It is produced in Fujian, Taiwan and Guangdong, and is often cultivated everywhere.It is mainly planted in gardens in Fujian, Guangdong, Guangxi, Jiangxi, Yunnan, Guizhou and eastern Sichuan, and in pots in Jiangsu, Zhejiang and northern China, and winters in greenhouses in winter.It is also distributed in southern Japan, Philippines and Indonesia.Cycads like warm and humid environment. They are not resistant to cold and grow very slowly. Their life span is about 200 years.In the tropical and subtropical south of China, trees over 10 years old bloom and bear fruit almost every year, while cycads cultivated in the Yangtze River basin and northern regions often do not bloom all their lives, or occasionally bloom and bear fruit.[5]
Cycas is a beautiful ornamental tree species, which is widely cultivated. Its stems contain starch and can be eaten;The seeds are oily and rich in starch, slightly toxic.[5]
The pericardium is wrapped into an ovary, and the ovule is in the ovary. The endosperm is formed after fertilization, and has a real flower. The main part of the flower is the stamen and pistil. In addition, it often has a calyx and corolla;Pollen grains remain on stigma and cannot contact ovule directly.[6]
Reproductive mode
Angiosperm is a group with many species, wide distribution and strong adaptability in modern plant kingdom.One of the outstanding characteristics of angiosperms is that they have real flowers, so angiosperms are also called flowering plants.The appearance of flowers represents a highly evolved and characteristic part of plant reproduction.The reproduction of angiosperms is the most sophisticated among all plants.Angiosperms produce new individuals through sexual reproduction, which is carried out in flowers. It is the whole process from the formation of sperm and egg to the formation of embryo and endosperm through fertilization.[3]
The flower of angiosperm is composed of calyx, corolla, stamen and pistil.The main function of calyx and corolla is to protect flowers and attract insects to transfer pollen.The middle of the flower is the stamen and pistil, which are the female and male organs of the flower.A stamen consists of filaments and anthers, which produce pollen grains.There are two forms of mature pollen grains in internal structure, one is containing aVegetative cellAnd a germ cell, such as the pollen of cotton and lily;The other is pollen containing one vegetative cell and two sperm, such as wheat and cabbage.Spermatozoa are formed by the division of germ cells. The division of germ cells may take place in pollen grains, or in pollen tubes that grow after pollen germination.[3]
The pistil is divided into three parts: stigma, style and ovary, which are shaped like a vase. There are 1 to many ovules on the inner wall of the ovary.The ovule is the place where the plant "fetus" grows. In the early stage, there was a sac in the middle of each ovule, called the embryo sac, which was formed byBlastocyst mother cellFormed by meiosis.Under the microscope, it can be seen that the mature embryo sac contains one egg cell, two helper cells and threeAntipodal cellAnd one with two polar nucleiCentral cell。[3]
When plants bloom, mature pollen is transported to the stigma of the same plant's pistil by wind or insects. Stimulated by the mucus on the stigma, pollen grains begin to germinate and form pollen tubes.The pollen tube passes through the style and ovary wall directly to the ovule, enters the embryo sac, and releases two sperm in the pollen tube into the embryo. One sperm combines with the egg cell to form a fertilized egg, from which the fertilized egg develops into an embryo;The other sperm combines with two polar nuclei to form a fertilized polar nucleus, from which it develops into endosperm.In this way, the fertilized ovule becomes a seed.[3]
When the egg cell is fertilized, the whole flower is stimulated and all parts of the flower change significantly.The style, stigma, stamen, corolla, etc. all withered, and most of the plant calyx also fell off, leaving only the ovary.A large amount of organic matter is constantly transported to the ovary, and the ovary begins to develop, expand, and finally form fruit.[3]
In angiosperms, the phenomenon that two sperm combine with egg cell and polar nucleus at the same time is called double fertilization.Double fertilization is not found in lower plants and animals, but is unique to angiosperms.The result of double fertilization not only makes the "fetus" carry the genetic characteristics of both parents, but also provides the endosperm for the development of the "fetus", as well as the genetic material of both parents.The offspring thus produced must have strong viability and adaptability, thus ensuring that angiosperms can survive and reproduce widely in a diversified natural environment.[3]
Time of occurrence
It began to appear in large quantities in the late Mesozoic in the geological history.[6]
Species distribution
This kind of plant is the most advanced in the plant kingdom, with a wide variety of nearly 300000 species.It is widely distributed around the world.It has great economic value.This category can also be divided intoDicotyledons and monocotyledonsTwo principles.[6]There are about 300-450 families in the world (the concept of families in each classification system is different). Most families are distributed in the tropics, and 2/3 of the species are limited to the tropics or its adjacent areas.There are about 25000 species in China, belonging to 291 families and 3050 genera.[7]
Key values
Soybean plant
Angiosperms occupy most of the land space of modern earth and are the main components of the world vegetation.The characteristics of angiosperms enable them to have internal conditions superior to other plants in the survival competition.The emergence of angiosperms makes the world the first time to see colorful, diverse, and luxuriant flowers and fruits. With the development of angiosperms' flower morphology and the storage of high-energy products in fruits and seeds, the animal kingdom (especially insects, birds, and mammals) that directly or indirectly rely on plants for living has obtained corresponding development and flourished rapidly.[3]
Angiosperms are closely related to human life, including ricebarley、Wheat, soybean sorghum, corn, potato and chestnut, etc;Vegetables include green vegetables, radish, winter melon, tomato, onion, etc;Oilseeds include rape, peanut, sesame, etc;The raw materials for light industry include sugar cane, tea, and straw cottonTextile raw materialsRicinus communis is a high-grade lubricating oil raw material, rubber is a national defense industry and transportation raw material, and bamboo is a building and weaving raw material;Fruit includes watermelon, apple and pineapple;Medicines include coptis chinensis and mint, and construction materials include camphor tree, white poplar, white birch, etc;Many angiosperms are also ornamental.[3]
Representative species
Soybean treeAlbiziaprocera（Roxb.） Benth.
Deciduous trees, 10-25m high, spineless;Branchlets slightly pubescent or subglabrous.Bipinnately compound leaves;There is a large oblong gland near the base of the total petiole;3-5 pairs of pinna, 15-20 cm long;Leaflets 6-12 pairs, nearly leathery, apex obtuse or slightly concave, base oblique, both sides sparsely appressed pubescent, midvein inclined to the lower edge;The petiole is about 2 mm long.The heads are arranged at the top of branches or leaf axilsPanicle；Flowers sessile;Calyx 2-3 mm long, glabrous;Corolla yellowish white, about 6 mm long, lobes lanceolate, about 2.5 mm long, top pilose;Ovary nearly sessile.The pod is banded, 10-15 cm long, 1.5-2.5 cm wide, flat, glabrous, with 8-12 seeds.Flowering from May to September;The fruiting period is from September to February of the next year.[8]
Produced in Taiwan, Guangdong and Guangxi.Born in low altitude sparse forests or shrubs.It is distributed from South Asia to Southeast Asia.[8]
This species is one of the fast-growing tree species, and has a pungent odor when felling.Sapwood is yellow white, heartwood is brown, hard, shiny, and has dark color texture.Wood is used for making wheels, farm tools and buildings, and is also a good fuel material.[8]
