It is the main class of plants and the next class of higher plants. Is the most primitive vascular plant. Most of them are herbs and few are woody plants. Sporophytes are divided into roots, stems and leaves. They have no flowers and reproduce by spores. Generation alternation is obvious, and asexual generation is dominant. Generally, it can be divided into five categories: Isoetes, Ferns, Lycopodium, Equisetum Equisetum and Ferns. A total of about 12000 species, mostly distributed in various provinces and regions south of the Yangtze River. Most ferns can be used for food (such as ferns), medicine (such as Osmunda japonica) or industry (such as Lycopodium). Include primitive vascular plants such as fern, equisetum and lycopodium. These three plants have the same development history, and all of them began to appear in Devonian. In the process of reproduction, all ferns need still water, and new plants can only live in fertile places. Therefore, it is not easy to see their traces in places that are dry all year round or where the seasons change greatly.
As for the classification system of pteridophytes, because botanists have different opinions, pteridophytes used to be regarded as a phylum, and its next five categories are: pteridophytes, Lycopodium, Isoetes, Equisetum (Wedelia) and Phyllostachys. The first four types are lobular ferns, which are primitive and ancient ferns, and there are few existing ferns. Pteridium aquilinum is a kind of large leaf fern, which is the most thoroughly evolved fern in modern times and the most prosperous fern. Qin Renchang, a pteridologist in China, divided pteridophytes into five subphylums, that is, all the above five classes were upgraded to subphylums. (Photo: the crown of ferns-Alsophila spinulosa)
A group of higher plants below seed plants. Formerly known as "fern". In the Paleozoic Devonian and Carboniferous, most of them were tall trees. From Permian to Triassic, most of them were extinct, and a large number of remains were buried underground to form coal seams. Modern life is mostly herbaceous, and a few are woody. Plants are divided into roots, stems and leaves, with vascular bundles, which do not bloom and reproduce by spores. Spores germinate to the ground to form prothallus, on which archegonium is produced, and fertilized eggs develop into embryos in archegonium. Generation alternation is obvious, and asexual generation is dominant. Most of China is located in the south of the Yangtze River. There are about 2600 species of Adiantum, Selaginella, Dryopteris, Lepidoptera and Alsophila in China. Many ferns are edible (such as ferns and Osmunda japonica), medicinal (such as Dryopteris crassipes and Lygodium japonicum) or industrial. /view/682 13.htm
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Gymnosperms
A lower class of seed plants. It has an archegonium, which is not only an archegonium plant, but also a seed plant that can produce seeds. They are called gymnosperms because their ovules have no ovary wall and no pericarp, and their seeds are naked.
Sporophyte is a plant, extremely developed, mostly trees, a few shrubs or vines (such as tropical vines), usually evergreen, with needle-shaped, linear and scaly leaves, and few flat broad leaves (such as bamboo and cypress). Most secondary xylem only has tracheids, and a few have vessels (such as ephedra). There are only sieve cells in phloem, but no companion cells and sieve tubes. Most female gametophytes have archegonia, and a few kinds of sperm have flagella (such as cycads and ginkgo biloba).
Gymnosperms appeared in Paleozoic, flourished in Mesozoic, and gradually declined due to geological and historical changes. There are about 800 species of modern gymnosperms, belonging to 5 classes, 9 orders, 12 families and 7 1 genus. There are 5 classes, 8 orders 1 1 family 4 1 genus 236 species and some varieties and cultivated species in China.
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An algae of the family Trematodaceae, a family of Cyanophyta. Cyanophyta is a primitive algae, which belongs to prokaryotes and has no organelle differentiation. Characteristics of undergraduate course: the algae body is composed of single or multiple filaments, and the rubber sheath is not obvious or does not exist; There are no atypical cells. /me? tn = baiduimage & ampct=20 1326592。 lm=- 1。 cl = 2 & ampword=%D4%AD%CA%BC%D4%E5%C0%E0
Bryophytes are green autotrophic terrestrial plants, and plants are gametophytes, which germinate from spores into protonema and then develop from protonema. Bryophytes are generally small, and the plants (gametophytes) that are usually seen can be roughly divided into two types: one is liverworts, which keep the shape of leaflike bodies; The other is moss, which begins to differentiate like stems and leaves. Bryophytes have no real roots, only pseudoroots (filaments composed of single cells or a series of cells with epidermal processes). The differentiation level of tissue in stem is not high, only the differentiation of bark and axis, and there is no real vascular bundle structure Most leaves are composed of a layer of cells, which can not only carry out photosynthesis, but also directly absorb water and nutrients.
Characteristics of bryophytes:
1. Mostly grows in humid environment, usually on stone surface, soil surface, trunk or branch. Small figure.
2. Some have no stems at all, and the roots and leaves are differentiated (moss), while others have the embryonic form of stems and leaves (moss).
3. Bryophytes have no vascular bundle structure, and their water transport capacity is not strong, which limits their size and height. There are false roots, but no real roots. The leaves are composed of monolayer cells, and the differentiation degree of the whole plant cells is not high, which is low in the plant kingdom.
4. There are generations alternating. The main body of bryophytes is gametophyte, which can produce gametes (sex cells). Gametophytes can form male and female reproductive organs. When the male genitalia is mature, the sperm is released, and the sperm swims into the female genitalia with water as the medium to fertilize the egg. The fertilized egg develops into sporophyte.
5. Sporophyte has spores (sporangia). Spores will drift with the wind when they mature. In a suitable environment, spores germinate into filamentous structures (protonema). Protonema produces buds, which develop into gametophytes.
Bryophytes produce multicellular sperm cells and sperm organs on the gametophyte during sexual reproduction. The archegonium is bottle-shaped, the upper part is narrow and called the neck, with 1 groove in the middle, the lower part is enlarged and called the abdomen, and there are 1 large cells in the middle of the abdomen called the egg. Sperm is good at making. Sperm has two flagella, which swim from water into the archegonium and combine with the egg. After fertilization, the egg cell becomes a zygote (2n), and the zygote develops into an embryo in the archegonium. Embryo develops into sporophyte (2n) according to the nutrition of gametophyte. Spores cannot live independently, but can only parasitize on gametophytes. The most important part of sporophyte is spore cover. The sporogenous tissue cells in the spore capsule undergo multiple divisions, and then undergo meiosis to form spores (N), which expand in a suitable environment and germinate into new gametophytes.
In the life history of bryophytes, from spore germination to gametophyte formation, gametophyte produces male and female gametes, which is a sexual generation, from fertilized egg to embryo, from embryo to sporophyte is called asexual generation. Sexual generation and asexual generation alternate with each other, forming generation alternation.
The gametophyte generation of bryophytes is dominant in life history and can live independently, while sporophytes can't live independently and can only parasitize on gametophytes, which is one of the obvious differences between bryophytes and other higher plants.
Bryophytes generally grow in damp and dark environment, and are the representative of the transition from aquatic to terrestrial. Bryophytes contain many kinds of compounds: lipids, hydrocarbons, fatty acids, terpenoids, flavonoids and so on.
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