Rhodophyta(Rhodophyta) algae, about 3000 species.Red algae, mostly multicellular, rarely unicellularalgae。Algae purplish redRose、Dark redIsochromatic.Most red algae grow inoceanIt is widely distributed and has many species. According to statistics, there are about 558 genera and more than 3740 species, and it is divided into two subclasses:Porphyra(Bangioideae) andEurhodophyta（Florideae）。Many of them have important economic value.In addition to food, it is also the raw material for medicine, textile, food and other industries.
Red algae, mostly marine, are found near tropical and subtropical coasts and often attach to other plants.The thallus is filiform, branched, feathery or flaky.The cells are connected with fine protoplasmic filaments.In addition to chlorophyll a, chlorophyll b, carotene and lutein, it also contains phycoerythrin and phycocyanin, so it is often red or blue.Red algalgerm cellCannot move.Female organ nameFruit spore, which is composed of mononuclear area and fertilization wire.Immobile spermIt is solitary in the sperm sac.Important edible red algae (such as laverRhododendron palmatum）The color and colloidal properties remain after cooking.In industry, red algae of the genus Chondrus are used as substitutes for gelatin in pudding, toothpaste, ice cream and preserved food.CorallinaSome species of (Corallina) are formingCoral reefAndcoral islandPlay an important role in the process.Mainly bygracilaria Agar prepared by red algae of Gracilaria and Gelidium is an important component of bacterial and fungal culture media.
Red algae grow in the oceans about 1.3 billion to 1.4 billion years ago, and are shaped like leaves.PlastidIn addition to chlorophyll andYellow pigmentIn addition, there are a lot of phycoerythrin, so it appears red.This is one kind of red algae.
Most plants are filamentous, leafy or dendritic, a few are unicellular, some are colony.Algae often have certain tissue differentiation, for example, some species have "cortex" and marrow.The cell wall is divided into two layers, the inner layer is composed of cellulose, and the outer layer is composed of pectinAgarPectin compounds peculiar to red algae, such as jackfruit gum.One pigment body, in the shape of star, belt, twisted belt or biconvex.Except for containingChlorophyll-aandChlorophyll b、CaroteneandxanthophyllIn addition, it also containsPhycoerythrinandPhycocyanin。Phycoerythrin is generally dominant, so the algal body is red or purplish red.The storage nutrients areRed algal starch(floridean starch) or red fucose (floridose).
Distribution range
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Rhodophyta(Rhodophyta) Most plants are distributed inseawaterAmong them, there are only more than 10 genera, and about 50 species are freshwater species.Freshwater species are mainly distributed in rapids, waterfalls and mountain water with cold air circulation.Marine species are distributed 100 meters from the seashore to the deep sea. The distribution of marine products is limited by the sea water temperature, and most of them are fixed.
Rhodophyta is about 558genus3740 species.Among them, about 200 species are born in fresh water, and the rest are marineMarine algae(now belonging to the kingdom Protozoa).
Not produced in the life cycle of red algaeZoospore，Asexual reproductionIt has many kinds of flagellateTelosporeSome produce single spores, such as Porphyra;Some productionTetraspore, such as Polysiphonia.Red algae are generallyDioeciousThe male organ of sexual reproduction is the sperm capsule, in which there are no flagellated sperm;The female organ is calledFruit cell(carpogonium), there is a fertilization wire (trichogyne) on the fruit cell, and there is only one egg in the fruit cell.After fertilization, the fruit cell undergoes meiosis immediately, producingFruit spore(carpopore), which develops into gametophyte plants;Some red algae develop carposporophyte without meiosis after fruiting cell fertilization. The carposporophyte is twice as large, unable to live independently and parasitic on the gametophyte.When fruiting spores are produced by fruiting spores, some of them undergo meiosis to form single fruiting spores and germinate into gametophytes;Some form diploid fruit spores without meiosis, develop into diploid tetraspores, and then generate tetrad through meiosis to develop into gametophytes.In the life history of Rhodophyta, some plants have no generation alternation, such as laver (Porphyra glycyrrhizae);Some have obvious generational alternation, such as Nemalion.
Red algaereproductionDevelopmental characteristics Red algae have the most complex life history. For example, the genus Gracilaria has three generations, including gametophyte generation, sporophyte generation andFruit sporeSomatic generation.Red algae can not only conduct sexual reproduction, but alsoAsexual reproductionThe sexual reproduction of red algae is completed through the combination of sperm and fruit cell.Asexual reproduction is carried out by a variety of static spores without flagella, some of which produceMonospore, such as laver;Some produce tetraspores, such as polytubules.Therefore, the reproductive behavior of red algae includes the formation and release of gametes and spores, and the combination of gametes.The sexual reproduction of red algae has great defects, because the male gametes (sperm) and female gametes (fruit cells) of red algae have no mobility, and the sperm can only survive for a few hours after release.Gracilaria gracilis sperm only survived for less than 5h.
Reproductive development of red algae is the result of comprehensive regulation of various environmental factors, such as light (light intensity, light quality and photoperiod), temperature, season, nutrition (inorganic and organic), biological factors (bacteria, animals), osmotic pressure, pH, waves and mechanical shocks, pollution and radiation.[3]
Key values
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Red algae have important economic value.Besides eatingMedical Science、spin、foodAnd other industrial raw materials.
Extract can inhibit obesity
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Recently, researchers from South Korea's National Busan University found that the extract of red algae (Gelidium amansi extract, GAE) can inhibit obesity induced by high-fat diet.Earlier studies have confirmed that high GAE intake for 12 weeksFatDietmouseHowever, no research has shown that GAE has the effect of reducing weight in obese mice.In this study, researchers analyzed the effects of GAE on body weight gain, fat mass, plasma, liver lipids, adipokine secretion and lipid metabolism factor expression in obese mice.The experiment lasted for 8 weeks. The subjects were obese mice, which were divided into control group and control group. The diet of the control group mice was normal diet, and the control group included five diets, all of which contained high fat.The researchers fed five groups of mice a new round of diet, Group 1 (high-fat diet), Group 2 (high-fat+0.5gGAE), Group 3 (high-fat+1gGAE), Group 4 (high-fat+2gGAE), and Group 5 (high-fat+75gGAE).After the 8-week test, the results showed that the weight loss of mice was the same as that of the conjugated linoleic acid (CLA) groupreduce weightFatty acids.The results also showed that the weight of GAE group mice was significantly lower than that of high-fat group mice.The final body weight of rats in groups 3 and 4 was basically the same as that of rats in CLA group.At the same time, even though the content of GAE in the diet is very low, it still has a role in weight control.[1]
Application in paper making
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abstract
Containing filamentsrootIt can be used as raw material for paper makingbleachSlurry.Red algae contain root like filaments, reddish cortical cells and medullary cells rich in mucoid carbohydrates.The main component of red algal pulp is the root filamentous body.The preparation method of high whiteness red algae slurry is to first remove the slime in the algae by heatingcarbohydrateAnd then treat the rest with bleach.
Preparation of red algae slurry
Previously, we had extracted pulp from some red algae varieties, including Ammansi's broccoli, rough broccoli, Chilean broccoli, hard broccoli, winged chicken hair, and bright leafSalsola cristata, hornstone cauliflower, long thornCauliflower。The shape and inner fiber content of different kinds of red algae are different, and the characteristics and content of viscous carbohydrates in medullary cells are also different.[2]
Representative plants
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Porphyridium
It belongs to Porphyra of Porphyra subclass.The plant body is a single cell with a round or oval cell center.The carrier is star shaped, in the middle axis, withProtein nucleus, NoneStarch sheath。They often live on wet ground and in corners of walls, and can be used for pure cultivation.
Porphyra
It belongs to the subclass Porphyra, and the algal body is a thallus composed of single layer or two layers of cells, which is purple red, purple or purple blue. The base is fixed to the substrate with a fixator, without a stalk or with a short stalk, generally 20~30cm high and 10~20cm wide.The cells are mononuclear, with 1~2 stellate pigment bodies, central axis, and protein nuclei.The growth of algae is diffuse.Porphyra glycyrrhizae, Porphyra orbiculata and Porphyra elongata are commonly distributed and cultivated in China.This article takes P. tenera as an example to understand the life history of laver plants.Porphyra glauca isMonoeciousPlants produce sexual organs when the water temperature is about 15 ℃.Any one of the algaeVegetative cell, can be transformed intoSperm sac, whichProtoplastIt divides into 64 sperm.The fruiting cell is formed by a common vegetative cell with slight metamorphosis. One end is slightly raised and protrudes from the surface of the algal colloid, that isZygotic silkThere is an egg in the fruit cell.After releasing, the sperm floats to the fertilization wire with the water flow, enters the fruit cell and combines with the egg to form a double zygote.After meiosis and ordinary division, the zygote forms 8 haploid fruit spores;When the fruit spores are mature, they fall on the shells of clams, oysters or other mollusks, germinate into the shells, and grow into single row branched filamentous bodies, that is, crustaceans;Conchospore is produced by Chaetomium spp., which germinates into summer Porphyra hainanensis with a diameter of about 3mm. When the water temperature is about 15 ℃, the Chaetospore can also directly develop into large Porphyra hainanensis.In summer, due to the high temperature in the water, it can not develop into large laver. Porphyra parviflora produces a single spore and develops into Porphyra parviflora;When the water temperature was about 15 ℃ in late autumn, the single spore germinated into large laver.Therefore, in the north, the growth period of large laver is from November to May of the next year.
Polysiphonia
It belongs to RhodophytaCelestiales, which is the most common algae in the sea water. There are about 150 species in this genus.The plant body is a filamentous body with multiple rows of cell branches. The filamentous bodies of some species are differentiated into erect filamentous bodies and creeping filamentous bodies. The base is fixed to the seaside rocks with a single celled rhizoid, about 3-20 cm high.The center of the filamentous body is composed of a row of thicker cells, called the central axon, which is surrounded by 4-24 thinner cells, called the peripheral axon.
The plant body of the genus Polysiphyllum has haploid female and male gametophytes, and diploidFruit sporophyteAnd tetrasporophyte.The gametophyte and tetrasporophyte are identical in appearance and typicalHomomorphic alternation of generations。Sperm sacThe fruit cell is born on the reproductive filamentous body on the upper part of the female gametophyte.When fruit cell is produced, a specialCircumaxial cell(also called supporting cells), from which four cell carpogonal filaments are produced.The top cell of the fruit spore silk body is the fruit cell with the fertilization filament. The fruit cell nucleus divides into 2, the lower nucleus is the fruit cell nucleus, and the upper nucleus is the fertilization filament nucleus. Later, this nucleus degenerates.Spermatozoa enter the fruit cell from the fertilization wire and combine with the egg.meanwhileSertoli cellA few more cells, called helper cells, were born.The fruiting cell is connected with the supporting cell through the auxiliary cell below it.The zygote nucleus divides into 2, enters the supporting cell, and continues to divide in this cell, and other nuclei degenerate.At this time, many sporogenous filaments occur in the supporting cells, and the nuclei in the supporting cells move to the sporogenous filaments.The sporangium is formed at the end of the sporangium. Each sporangium has two nuclei. At the same time, the supporting cells fuse with the surrounding cells to form a sporangium mass, which is generally calledAscocarpFruit spores germinate to form diploid tetraspores.The tetrad sporangium is formed on the tetrad sporophyte. After meiosis, four single spores are formed, called tetrads. The tetrads germinate to form male and female gametophytes.
The common freshwater products of red algae are Batrachospermum, Nemalion, Corallina, Ceramium, Rhodomela and Gelidium.
Rhodophyta
The economic value of Rhodophyta is very high.Among red algae, laver is a kind of foodalgae, which contains richproteinIt is not only nutritious, but also delicious.In addition, Gelidium amansii and Gloiopeltis furcata can be eaten.Caloglossa leprieurii and Digenea simples are commonly used childrenAnthelminticDrugs.From the genus LycorisRiver hedgeGracilariaunicornAgar extracted from Eucheuma plants is widely used in the pharmaceutical industry and textile industry as a culture medium.
