algaeIt is a kind of relatively primitive and ancient lower biology.Algae have simple structure, no differentiation of roots, stems and leaves, and are mostly unicellular, colony or multicellular thallus.For example, Chlorella is unicellular, Volvox belongs to colony, and Laminaria is leafy.Algae contain photosynthetic pigments such as chlorophyll, which can carry out photosynthesis and are autotrophic organisms.[1]
From a historical perspective, the first record of "Zao" in Chinese history was in the Book of Songs, a collection of poems written in the Spring and Autumn Period and the Warring States Period.The Book of Songs · National Style · Apple Picking records: "In order to pick algae? In that line of scribbling";The Book of Songs · Lu Song · Pan Shui records: "thin picking of algae", etc.This shows that people had already known about "algae" and took the initiativecollection。[2]
There are about 30000 species of algae, which are mainly distributed in fresh water or sea water, including freshwater algae andMarine algaeTwo, includingCyanophytaCyanophyta、EuglenophytaEuglenophyta、DinoflagellatePyrrophyta、ChrysophytaChrysophyta、XanthophytaXanthophyta、DiatomaBacillariophyta、ChlorophytaChlorophyta、RhodophytaRhodophyta、Phaeophytaphaeophyta。The body types are diverse, including single cell, colony (formed by many single cells, and the cells have no close physiological connection), multicellular filamentous body and thallus;Higher species have simple tissue differentiation.Algae vary greatly in size, and the small ones are only a few microns, which can only be seen under a microscope;Larger visible to the naked eye, the largest body is more than 100 meters long.Overbreeding of some species may causered tide(Marine)algal bloom(fresh water), etc.[3]
① There are all kinds of algae,oxygenAlgae have no differentiation of rhizomatous leaves, so actually the algal body is a simple leaf, also known as a thallus;
Algae vary greatly in size, and the smallest diameter is only 1-2 microns,naked eyeThe largest one is more than 60 meters long;The morphology varies greatly, including single cell, colony and multicellular.Each body of the population is composed of many single cell individuals.Multicellular individuals haveFilamentous body, vesicles and pellicles, which also have shapes similar to roots, stems and leaves, but do not havehigher plantSuch internal structure and function.Most reproductive organs are composed of single cells.The zygote does not develop into embryo in the mother.They mainly live in water, and some live in wet rocks, tree trunks, soil surface or interior.In case of earthquakeVolcano eruption. Surviving on the new substrate formed after flooding, it is one of the pioneer plants in the new living area.
algaeplant cellIt contains a variety of pigments, and different pigment composition marks different directions of evolution, which is the main basis for classification.But all algae containChlorophyll-aAnd photosynthesis system II, and can use water as a hydrogen donor to releaseoxygen。At present, free oxygen in the atmosphere is mainly the product of photosynthesis, most of which is produced by algae.The pigments of algae mainly include 4 types: chlorophyllPhycobiliprotein、CaroteneAnd lutein, in which, except chlorophyll a,Beta caroteneIt is also commonly found in various algae, only inCryptophytaIt's just a small number.In addition,Rhodophyta,, and Cryptophylum also contain phycobiliproteins;CryptophytaDinoflagellate、Xanthophyta、Chrysophyta、DiatomaandPhaeophytaContaining chlorophyll c;Prochlorophyta DoorsPleurophylum、ChlorophytaandCharophytacontainChlorophyll bSome species in Rhodophyta contain chlorophyll d.A small number of algaeSaprophyticOr parasitic life, gradually losing chlorophyll and becoming algae without pigment.[4]
Growth and reproduction
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Algae
The reproduction of algae includes vegetative reproduction, asexual reproduction and sexual reproduction.There are many methods of vegetative reproduction, including special vegetative branches, such as the reproductive branch of black top algae, which will grow independently into new individuals after falling off the ground;DependentRhizoidFor example, the sea fan algae;Others rely on discoid larvae for summer or winter.Asexual reproductionIt mainly depends on zoospores, which generally have 1~4Flagellum，chloroplastandEyespot, Nocell wall, have the ability to swim freely;There are also many spores lacking flagella and therefore no swimming ability, such as endospores of Cyanophyta and those of RhodophytaTetraspore, ChlorophytaChlamydosporeEtc.Sexual reproductionrely ongamete, can be same or different.Homogamy consists of gametes with the same shape and size that are close to each other and fuse to form thick walled zygotes, while heterogamy consists of gametes with different sizes or even shapes that fuse to form zygotes.Egg mating is a kind of heterogamy. The female cell is large and generally cannot swim, while the male cell is small and has two flagella and can swim freely.The eggs of red algae are particularly special,OocystThe fruit cell is a bottle like structure. The egg is at the bottom of the bottle, and the bottleneck isZygotic silk, andspermstaySperm sacIt cannot swim inside, but drifts with the water. When it meets the fertilizing silk, it sticks to it, and the sperm breaks out of the capsule. Along the fertilizing silk, it enters the fruit cell and combines with the egg to form a zygote, which immediately develops into a diploid fruitSporophyte, parasitic on female individuals.Fruit sporeFructospores are produced during somatic maturation and develop into independent sporophytes.Cyanobacteria have no sexual reproduction.
System classification
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Prokaryotic Algae
Algae
Cells areProkaryotic cell, mainly Cyanophyta, which is sometimes promoted to one kingdom, namely Cyanobacteria kingdom.Single cell individuals or groups, or filaments with cells arranged in strings to form algal filaments (cell lines), which are unbranched, pseudobranched or true branched.Nucleoplasm, no nuclear membrane;The chromatin region is mainly composed of thylakoids and their related structures, phycobilisomes and glycogen particles, with photosynthetic pigments such as chlorophyll-a, phycobilin, carotene, carotenoid, etc., but without chloroplast membrane, it does not form chloroplasts;With cell wall.[3]
Cyanophyta
Simple algal plants, about 1500 species, are widely distributed, mostly in fresh water.Plants have single cells, colonies or filaments.The cell has no real nucleus,ProtoplastIt differentiates into two parts: periplasm and centroplasm.Periplasm is located at the inner side of the cell wall and contains chlorophyll a and phycocyanin (phycobilin), so it is generally blue-green, but has no carrier;The centroplasmic phase is located in the nucleus, without nuclear membrane and nucleolus, but with DNA, which is called pronucleus.The nucleus is divided into two layers, the inner layer is composed of cellulose, and the outer layer is a glial sheath composed of pectin.Asexual reproductionThe number of individuals is increased mainly by cell division, population disruption and filament disruption, with a few spores.Among common cyanobacteria, the unicellular chromococcus belongs to Chlorococcus, which grows on flower pots in greenhouses or wet rocks, and can also grow in fresh water;Microcystis in the group, which endangers aquatic animals in the floating water;There are also Oscillatoria, Nostoc, Anabeana, etc.Edible agaricNostoc commune, Nostoc flagelliformeNostoc flagelliformeEtc.
Prochlorophyta
Only one kind of protochlorella has been foundProchloron didemni。It was first discovered in 1975 in Baja California, Mexico. Now it has been found in many tropical waters, including the Xisha Islands in China and the Xishou Island in Sanya, Hainan Island.Single cell, grass green, aggregated on some gelatinous crustaceans in the upper part of the subtidal zone of coral reefs, especially sea squirts on dead corals;Some of them also grow on living algae, such as glia of hornwort, which is symbiotic with sponges.stayoptical microscopeThe protoplast is obviously divided into two parts: the colorless central area and the emerald green surrounding area, without nuclei and chloroplasts.Cell division, like that of Cyanophyta, is bifid.Photosynthetic pigment has βCaroteneAnd chlorophyll a andChlorophyll bThe average a/b ratio is 5.6~6.0, which is much higher than that of other green algae (2~3).It is generally believed that protogreen algae evolved from blue algae;Others believe that proto green algae may have occurred more than 2 billion years ago before the appearance of sea squirts, which is an intermediate organism between blue algae and green algae. They not only inherit the chlorophyll a of blue algae, but also produce chlorophyll b, playing a leading role in the production of green algae.
Eukaryotic Algae
Eukaryotic Algae It is a group of lower autotrophic eukaryotic plants that can carry out photosynthesis without differentiation of roots, stems and leaves. It appeared about 1.5 billion to 1.4 billion years ago.The morphology includes single cell, various populations, filamentous body, thallus, tubular body, etc.The size ranges from several microns to several meters (kelp), or even 100 meters (giant algae), with simple structure and no obvious tissue differentiation.A few species have differentiation of epidermis, cortex and marrow, such as kelp.A plant is often called an original plant.Most of them have cell walls, and only cryptophyte, euglena, and most chrysophyta are absent;The nuclei are all eukaryotic, with nuclear membrane, nucleolus and chromosome;Organelles include plastids, mitochondria, endoplasmic reticulum, golgi apparatus, vacuoles, etc;Photosynthetic apparatus (color carriers) include cup, disc, band, star, block, mesh and other forms. Green algae and charophytes form simple grana, while other algae do not form grana.Photosynthetic pigments include 4 kinds of chlorophyll (chlorophyll a, b, c, d)CarotenoidsClass (5 carotenes and many luteins), phycobilins（Red algae、CryptophyteAnd dinoflagellatePhycobilin）；Chloroplasts are green photosynthetic apparatus containing chlorophyll a and b;The pigment body is a photosynthetic apparatus containing chlorophyll c or d, which is brown, yellowish brown or purplish red.Reproduction includes vegetative reproduction (cell division, algal disconnection, propagation of twigs)Asexual reproduction(GeneratedAsexual spore, i.eZoospore, Acinetobacter, etc.) and sexual reproduction (homogamyHeterogamyEgg reproduction);The zygote or fertilized egg breaks away from the mother body and produces new algae;The zygote or zygote does not develop into an embryo.Most eukaryotic algae are born in fresh water, sea water, brackish water and other water bodies, as well as in wet soil surface, rock surface, bark, walls and other places, and some species are born inAlpine snowSome are symbiotic with fungi and other organisms.Life forms include planktonic, attached, fixed, benthic, etc.[3]
Chlorophyta
There are about 8600 species, the largest phylum of algae.Algae can be divided into single cell, colony, filamentous body, thallus, tubular multinucleate and other types.The cell wall is made of cellulose.Each cell has a certain form of chlorophyll, such as cup, ring, star, mesh, etc;Chloroplasts contain chlorophyll a, bCaroteneAnd lutein, so the plant is green.There are one or more protein nuclei in chloroplasts.The stored nutrients are mainly starch, but also lipids.There are various ways of reproduction, both asexual and sexual reproduction are common, and many species have generational alternation.The vegetations of a few species and the spores or gametes of most species mostly have 2 or 4 terminal flagella of equal length, and a few have 1, 8 or more flagella of tail whip type.It is widely distributed, but most of it is produced in fresh water, and a few of it is distributed on moist soil surface or marine products.Generally, it can be divided into two classes: Chlorophyceae and Conjugatophyceae.Such as Volvox, Chlamydomonas, Spirogyra, Chlorella, Pandorina, etc.
Charophyta
Plant body has differentiation similar to root, stem and leaf.The stem is divided into nodes and internodes. On the nodes, there are twigs equivalent to leaves in rotation. Some species are covered with calcium or colloid outside.There are small discoid or oval pigment bodies in the cells;Photosynthetic pigments are chlorophyll a and b, and βCaroteneLutein and other carotenoids;Non protein nucleus;The assimilation product is starch.Single core.There are large central vacuoles in mature cells.onlyEgg copulationThe reproductive organs are developed, with spermatophores and egg collectors. They are born on the nodes of twigs or at the base of twig rings. When they are mature, they are mostly orange red or golden brown. The sperm cells have two flagella of equal length, and the top is inclined to one side.Some species can produce bulbils on the nodes of underground rhizoidsVegetative reproduction。It is divided into 1 class and 3 orders (Orthocharophyta Sycidiales, dextral Charophyta Trochiliscales, and sinistral Charales). Currently, there are only six genera and about 400 species of Characeae, which belong to the sinistral Charophyta, and more than 150 species have been reported in China.It is widely distributed in various fresh or brackish waters, especially in paddy fields, ponds, lakes and marshes.
Euglenophyta(Euglena)
There is no cell wall, and most of them are flagellate swimming monocytes.Most species contain pigment bodies similar to those of Chlorophyta, with or without protein nuclei. Only a few species become colorless without pigment bodies, but the storage materials are starch like parastarch and fat.On one side of the storage bubble, there are 1 to several contractions for excretion;There is often a photosensitive eyespot on the wall of the storage bubble.The nutrition modes include plant, pure animal or saprophytic.It is widely distributed.Most of them are produced in fresh water, a few in salt water and brackish water, and a few grow on wet soil or in ice and snow. There are also parasitic or epiphytic species.There are about 40 genera and more than 1000 species in the world.Only Euglenophyseae includes two orders: Euglenales and Colaciales. The former includes free moving species and is divided into three families: Euglenaceae, Astasiaceae, and Peranemaceae;The latter includes epiphytic species, only the Euglenidae Colaciaceae.Most common species belong to Euglena, Phacus and Trachelomonas of Euglena family.
Diatoma
Single cells or connected to each other to form various groups.The cell wall consists of two fused silica halves;The larger half set outside is called the upper shell, and the smaller half set inside is called the lower shell.The mode of reproduction is mainly cell division. The upper and lower shells of the mother cell form the upper shell of the daughter cell, while the lower shell is secreted and formed respectively.The pigments mainly include chlorophyll a, c, β - carotene, α - carotene and lutein.It can be divided into 2 classes:Central DiatomaCentricae is round and radially symmetrical. The patterns on the shell surface are radially arranged from a point in the center to the periphery, and there are many seafood.Penatae is long or navicular, and the patterns are arranged symmetrically on both sides. The surface is lined with lines, ribs, and longitudinal cracks (shell cracks). The central part of the shell surface is thickened, called the central node, and the two ends are called the end nodes. Fresh water is abundant.It is widely distributed in fresh water, brackish water and sea water.It is commonly seen as Cyclotella, Pinnularia, Cossinodiscussion, Navicula, etc.
Chrysophyta
Algae are unicellular or integrated groups, floating or attached.The carrier is golden brown and contains many kinds of chlorophyllCarotene。The species swimming in the single cerebellum have no cell wall, but have cell wall. The main component is pectin.Most of them have one or two terminal flagella (three are rare), which are equal or unequal in length.The stored food is oil and wheat albumin.Reproduction methods include fragmentation (population type), division and generationZoospore(non flagellated species);Sexual reproduction is rare and belongs to homogamy.It is mainly distributed in clear fresh water with low temperature.There are about 300 genera and 6000 species.Three quarters of them are freshwater products, and the rest are marine products.Such as Botrydium, Ochromonas, Chlorogibba and Tribonema.
Dinoflagellate
Most of them are single cells, nearly spherical, with back and abdomen, and have two unequal flagella arranged asymmetrically.With or without cell wall, the former is divided into longitudinally divided dinoflagellate and transversely divided dinoflagellate.The main pigments are chlorophyll a and c, β - carotene and several special lutein. The content of yellow pigment is about 4 times higher than that of chlorophyll, so the algae is yellow green, golden brown to dark brown.The reproduction is dominated by longitudinal cell division, and a few species can produce spores.There are about 1500 species, such as Peridinium and Ceratium.It is widely distributed, both in fresh water and sea water, especially in tropical oceansmarine animalThe main bait of.Due to the eutrophication of coastal waters, dinoflagellate algae (e.g. noctilucaNoctiluca scintillans, Marine ProrocentrumProrocentrum micansAnd so on), forming water blooms, discoloring the water, giving off a fishy smell, and forming red tide.When the density is too high, dead algae will breed saprophytic bacteria, and the dissolved oxygen in the water will drop sharply, and dinoflagellate toxin will be produced, which will do great harm to fish, shrimp and shellfish.After death, the seafloor was deposited and became the main fossil in the Paleozoic oil strata. Therefore, dinoflagellate fossils are often used as a basis in oil exploration.
Xanthophyta
The plant body types are unicellular, colony, multinucleated tubular or filamentous.The cell wall contains a large amount of pectin, most of which are composed of two equal or unequal shaped segments;The cell wall of the tubular or filamentous body is formed by two "H" shaped segments.Moving individuals and zoospores have two unequal flagella, and few have one flagellum.The pigment body contains chlorophyll a, c, β-CaroteneAnd lutein.Pigment bodies are usually yellow green, 1 to many, discoid and flaky.The reproduction is mainly spores.Most species like calcium, especially living in semi flowing and clean water.Most species can be used as bait for fish.There are about 75 genera and more than 370 species, which can be divided into 5-6 orders.It is commonly seen as yellow filamentous algae Tribonema, yellow tubular algae (Ophiocystium), etc.
Phaeophyta
The plant body is multicellular, and some have tissue differentiation.The cell has a wall and is divided into two layers. The inner layer is cellulose and the outer layer is alginate.At the same time, the cell wall also contains fucoidan.Chromophore contains chlorophyll a, c, β-CaroteneAnd 6 kinds of lutein.One kind of lutein is called fucoidin, which makes the algae brown.The stored food accumulated by cell photosynthesis is mainly brown algal starch and mannitol.Sperm andZoosporeGenerally, there are two unequal length lateral flagella, and the one that protrudes forward is longer, which is the velvet whip type;The one protruding backward is short and tail whip type.Most of them are marine, only Phaeophyceae, about 250 genera and 1500 species, and freshwater, only 8 species, which can be divided into 13 orders.Common, such as kelpLaminaria japonica, Thallus Laminariae in Khumbu, Macrocystis, Sargassum, Undaria pinnatifidaUndaria pinnatifida, CornflowerPelvetia silguosaEtc.
Rhodophyta
Most plants are multicellular, and a few are unicellular.Some species have certain tissue differentiation.The inner layer of cell wall is fibrous and the outer layer is pectin.The carrier contains chlorophyll a, d and β-CaroteneAnd lutein, in addition, phycobilin and phycocyanin, so most algae are red.Red algal starch and red algal sugar are stored in.There are about 760 genera and 4410 species, most of which are marine, and a few are freshwater.The depth of growth in seawater can reach 200 meters. In the intertidal zone, it is mostly found in the shade of rocks. In rock crevices or marshes, there are also a few people who prefer to live on exposed rocks with strong wind and waves.Most species are fixed on rocks or other growth substrates, and some are epiphytic or parasitic on other algae.There are some nutritious and delicious food species, such as Porphyra, Eucheuma, Gloiopeltis, etc;There are also some important economic species, which are used to extract agar and carrageenan, such as Gelidium, Gracilaria and other genera.
economic value
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The economic importance of algae is mainly reflected in:
① Algae fix inorganic carbon through photosynthesis to convert it intocarbohydrate, so thatWater productivityProvide foundation.oceanFloating algaThe total productivity of is estimated to be 31 × 109 tons of carbon per year.In the transformation of the food chain, 1 kg of fish meat needs about 100~1000 kg of planktonic algae, soPlanktonic algaeThe resource rich sea areas are all the places where the world famous fishing grounds are located, and the production of planktonic algae is an indicator to estimate the marine productivity.
② In pond fish cultureWater colorJudge the water quality, and the water color is determined by algaedominant speciesAnd its reproduction degree.As red as bloodEuglenaRed in dominant speciesalgal bloom, description of water qualityLean and poor；chlamydomonasWhen dominant, it shows dark green bloom and sticky blisters, indicating fertile water quality;Microcystis andOscillatoria 、AnabaenaWhen the pool water is dominant, it is copper rust colored yarn flocculent bloom, and the odor is harmful to fish;Bluish nakednessDinoflagellateThe dominant blue blooms are the cultured silver carp, bighead carp, carp, crucian carpNon crucian carpOne of the typical water quality of high-yield fish ponds, but excessive reproduction will also worsen the water quality and cause fish flooding.In addition,Platymonas、dunaliella 、chlorellaetc.Unicellular algaeHigh protein content, including shellfish, shrimp andHolothuriansImportant natural food for breeding.
③Nitrogen fixing cyanobacteriaIt is not only an important organism providing compound nitrogen on the earth, but also an important available biological nitrogen fertilizer resource.At present, there are more than 120 kinds of nitrogen fixing cyanobacteria, and the amount of nitrogen fixation in rice field per hectare is 16-89 kg.
⑤ The industrial use of algae is mainly to provide various alginate.Kelp, kelp, undaria pinnatifidaStaghorn、Sargassum fusiformeIt can be used for extracting iodine, mannitol andAlginRaw materials.Giant alga, Phyllophyllum spp. and other Sargassum spp. can also be used as raw materials for extracting algin.Alginate is widely used in food, paper making, chemical industry and textile industry.From cauliflowerGracilariaAgar can be extracted from Chinese angelica and used for medicinechemical industryThe raw material and the culture medium for microbiological research.Keratophylla from RhodophytaEucheuma, Chinese fir alga, sand vegetable, gingko alga, forked algaeCentipede、HailuoIt can be extracted from the algae such as Yigucao, which can be widely used in the food industrycarrageenan。
In terms of food value, Lu Ji from the Wu Kingdom of the Three Kingdoms《Maoshi Vegetation, Birds, Animals, Insects and Fish》It is recorded in the book: "There are two kinds of algae that grow on the bottom of the water... Both algae can be eaten. They can be boiled to remove the fishy smell, and the rice, flour and grits can be steamed to become the raw material, which is very smooth and beautiful. People in Jingyang are hungry to eat grain";Guo Pu of the Jin Dynasty recorded in Er Ya Zhu that "seaweed... can also be eaten";Jia Sixie in the Later Wei Dynasty《Qi People's Essential Skills》It is recorded in the book: "Algae... when cooked, the fishy smell will be removed. Rice flour and grits will be steamed into Ru, which is delicious. People in Jingyang are hungry to eat grain";Liang Ke's Family in the Song Dynasty《Three Mountain Annals of Chunxi》It is recorded that "seaweed... Yangzhou people feed on it".These records show that Chinese ancestors have continuously discovered and excavated the edible value of algae. The first time to discover the edible value of such plants was in the Han Dynasty.Li Shizhen of the Ming Dynasty recorded in his Compendium of Materia Medica that "seaweeds are taken from various places near the sea, and also used as seaweed. They are a kind of name, and the goods are everywhere." It can be seen that by the Ming Dynasty, algae plants had been circulating in different regions as a common vegetable.[2]
In terms of medicinal value, the Shennong Classic of Materia Medica records that "seaweed tastes bitter and cold. It is mainly used to treat gall gas, lower neck nucleus, break loose and stagnate gas, carbuncle and swelling, firm qi in the abdomen, and edema in the lower 12";Written in Liang's《Other records of famous doctors》Record: "Seaweed is salty and non-toxic. It is mainly used to treat skin accumulation, ulceration, retention of air and heat, and facilitate urination";Tang Dynasty《Newly revised materia medica》Record: "Seaweed tastes bitter, salty, cold and non-toxic. It mainly contains gall gas, lower neck nucleus, broken and scattered qi, carbuncle, mass, firm qi, abdominal ringing up and down, and lower twelve edema. It can heal the accumulation of skin, burst, retain air and heat, and facilitate urination";The Compendium of Materia Medica of the Ming Dynasty recorded that "algae...... Sweet, cold, slippery, non-toxic", and cited the Tang Dynasty's "Herbal Materials" record: "to eliminate violent heat and dysentery, quench thirst, and mash juice. Children's red and white rash, fiery hot sores, mash and seal";In the Qing Dynasty's "Materia Medica Encounters the Plains", it was recorded that "seaweed is bitter, salty, cold, toxic, and anti liquorice", and cited《Shennong's Herbal Classic》According to the records of, "It mainly focuses on the formation of qi in the gall, spreads the hard nucleus in the neck, cures the hard qi in the abdomen due to carbuncle, thunders in the abdomen, and 12 kinds of edema in the lower part".These records show that Chinese ancestors have begun to pay attention to the medicinal functions of algae from a very early time, and have been constantly digging and sorting out.Modern research also confirms thatSargassaceaeThis plant has medicinal value.[2]
