Figure : Common Orange Lichen

Figure : Moss (Bryophyte)

Figure : Ferns (Pteridophyte)

Figure : Gymnosperm

Figure : Passion Flower and Fruit

(Angiosperm)

General characters of algae

​

• Algae is a group of chlorophyll containing thalloid plants which bear unicellular or multicellular sex organs and the sex organs are NOT protected in the sterile jacket cells.
• An undifferentiated plant body is known as ‘thallus’. In thalloid plants, there is no differentiation of plant body into true roots, stem and leaves.
• The study of algae is known as PHYCOLOGY. The one who study algae is called Phycologist.
• In Eichler’s system of classification, algae are placed in the Division Thallophyta along with Fungi and Lichens.
• Algae are autotrophs (synthesize food using light energy)
• Algae differ from fungi in:

Presence of photosynthetic pigment – chlorophyll�Mode of nutrition (autotrophs)

• Majority of algae are in aquatic habitats (freshwater or marine), some algae are terrestrial also.
• Algae are present in all parts of the world including Arctic and Antarctic regions (universal occurrence)

Sex organs

• There are about 1800 genera and about 21,000 spp.
• Variation in size eg. Chlamydomonas, Chlorella are unicellular while Macrosystis are ultimately reaching 30 to 80 metres (100 to 260 ft).
• Sex organs are unicellular or multicellular
• Sex organs lack jacket cells around them (naked sex organs)
• If jacket cells are present, they have different origin
• There is a progressive complexity in the reproduction of different algal groups
• Embryos is not formed after zygote formation
• Show distinct alternation of generation
• Cellular organization may be prokaryotic (blue green algae) or eukaryotic (all other algae)

​

Isogamy 

It is a form of sexual reproduction that involves gametes that involves gametes of similar morphology that involves gametes of similar morphology (similar shape and size), differing in general only in allele that involves gametes of similar morphology (similar shape and size), differing in general only in allele expression that involves gametes of similar morphology (similar shape and size), differing in general only in allele expression in one or more mating-type regions.

Because both gametes look alike, they cannot be classified as "maleBecause both gametes look alike, they cannot be classified as "male" or "femaleBecause both gametes look alike, they cannot be classified as "male" or "female." Instead, organisms undergoing isogamy are said to have different mating types, most commonly noted as "+" and "−" strains, although in some species there are more than two mating types (designated by numbers or letters). 

FertilizationFertilization occurs when gametes of two different mating types fuse to form a zygote.

​

• There are several types of isogamy. Both gametes may be flagellatedThere are several types of isogamy. Both gametes may be flagellated and thus motileThere are several types of isogamy. Both gametes may be flagellated and thus motile. This type occurs for example in algae such as some but not all species ofChlamydomonas.
• With non-motile cells: In another type, neither of the gametes is flagellated. This is the case for example in the mating of yeast. Yeast mating types are commonly noted as "a" and "α" (alpha) instead of "+" and "-".
• Conjugation: Another, more complex form, is conjugation (similar to the exchange of genetic material through a bridge in some the green algae, the Zygnematophyceae, e.g., Spirogyra. These algae grow as filaments of cells. When two filaments of opposing mating types come close together, the cells form conjugation tubes between the filaments. Once the tubes are formed, one cell balls up and crawls through the tube into the other cell to fuse with it, forming a zygote.
• In ciliatesIn ciliates, cell fission may follow self-fertilization (autogamy), or it may follow conjugation (exchange of nuclei).
• Spirogyra conjugation: In many cases, isogamous fertilization is used by organisms that can also reproduce asexually through binary fissionSpirogyra conjugation: In many cases, isogamous fertilization is used by organisms that can also reproduce asexually through binary fission, buddingSpirogyra conjugation: In many cases, isogamous fertilization is used by organisms that can also reproduce asexually through binary fission, budding, or asexual spore formationSpirogyra conjugation: In many cases, isogamous fertilization is used by organisms that can also reproduce asexually through binary fission, budding, or asexual spore formation. The switch to sexual reproductionSpirogyra conjugation: In many cases, isogamous fertilization is used by organisms that can also reproduce asexually through binary fission, budding, or asexual spore formation. The switch to sexual reproduction mode is often triggered by a change from favorable to unfavorable growing conditions. Fertilization often leads to the formation of a thick-walled zygotic resting spore that can withstand harsh environments and will germinate once growing conditions turn favorable again.

​

​

Anisogamy 

• Anisogamy (also called heterogamy) is the form of sexual reproduction) is the form of sexual reproduction that involves the union or fusion of two gametes, which differ in size and/or form. (The related adjectives are anisogamous and anisogamic. The smaller gamete is considered to be male (sperm cell. The smaller gamete is considered to be male (sperm cell), whereas the larger gamete is regarded as female (egg cell).
• There are several types of anisogamy. Both gametes may be flagellatedThere are several types of anisogamy. Both gametes may be flagellated and therefore motileThere are several types of anisogamy. Both gametes may be flagellated and therefore motile. Alternatively, both of the gametes may be non-flagellated. This [which?] situation occurs in some algae and plants. In the red alga Polysiphonia, non-motile eggs are fertilized by non-motile sperm.

​

Oogamy

• Oogamy is the familiar and advanced form of sexual reproduction.
• It is a form of anisogamy (heterogamy) in which the female gamete (e.g. egg cell) is significantly larger than the male gamete and is non-motile. The male gametes are typically highly motile spermatozoa competing for the fertilization of the immotile egg.

Oogamous Type

Antheridium of Oedogonium

Macrandrous Nannadrous

Oogonium of Oedogonium

Occurrence of algae:

• Found in a variety of habitats (Fresh water, marine, on rocks, with in plants or animals)
• Aquatic forms are most common
• On the basis of habitat, algae are classified into three groups

1. Aquatic forms

2. Terrestrial forms

3. Algae of unusual habitats

​

�(1). Aquatic algae:�

Two types: Fresh water and marine forms

(a). Fresh water forms: 

Occurs in ponds, lakes, river etc.(Spirogyra)

(b). Marine water forms: 

Occurs in saline condition such as seas and oceans (Most of the Red and Brown algae such as Polysiphonia and Sargassum)

​

​

​

Chlamydomonas (Unicellular Flagellated Algae)

(2). Terrestrial Algae:

• Found in/on soil, rocks, moist wall, tree trunks etc.

Example: Vaucheria and Fritschiella found on the surface of soil

Vaucheria  Fritschiella

​

(3). Algae of unusual habitat:

• Halophytic algae: algae present in highly saline water (e.g.:Dunaliella)
• Epiphytic algae: algae grown on the surface of other plants/algae (e.g. Oedogonium)
• Epizoic algae: algae grown on animals such as snails and fishes (e.g. Cladophora grows on the shells of snails)
• Endozoic algae: algae growing inside the animals (e.g. Zoochlorella grow inside Hydra), Dunaliella (single celled algae)
• Symbiotic algae: Symbiotic (mutual) association with fungi in lichen, in Bryophytes (Anthoceros), in Pteridophytes (Azolla),gymnosperms (corolloid roots of Cycas) and in angiosperms.
• Parasitic algae: grow as parasite on plants or animals (e.g. Cephaleuros is a parasitic green algae grow on the leaves of many plants causing red rust diseases)
• Thermophytic algae: grow in hot springs. (e.g. Heterohormogonium)
• Fluviatile algae: algae found in rapidly running water such as water falls (e.g.: Ulothrix occurs in mountains water falls

​

Red Rust on Leaves by Cephaleuros

Dunaliella (single celled algae)

Thallus diversity in algae:

• Wide range or thallus variation in algae
• Thallus may be unicellular to multicellular and microscopic to macroscopic
• Plant size range from few micron to several meters

e.g. Chlamydomonas is a single celled algae whereas Macrocystis pyrifera, a marine brown algae, is multicellular, parenchymatous and several meters long.

• On the basis of thallus organization algae are following five types:-

(1) Unicellular forms (e.g. Chlamydomonas, Chlorella)

(2) Colonial forms (Volvox, Pandorina)

(3) Filamentous forms

(a) Un-branched filamentous (Spirogyra, Oedogonium)

(b) Branched filamentous (Cladophora, Pithophora)

(4) Siphonaceous forms (Vaucheria)

(5) Parenchymatous forms (Sargassum, Laminaria)

​

Largest Algae (Macrocystis pyrifera) 

An Algal Bloom of Blue Green Algae

Pigmentation in algae:

• Algae also shows great diversity in pigmentation
• Different groups of algae have different pigment composition
• Distribution pattern of pigments has great taxonomic significance in algae
• The classification of algae by Fritsch is primarily based of the pigmentation in algae
• Pigments in algae belongs to three major categories:

(1) Chlorophylls

(2) Carotenoids

(3) Phycobilins

​

�Distribution pattern of different pigments in different algal groups�

• All photosynthetic algae contain chlorophylls, carotenoids and Xanthophylls.
• Members of Cyanophyceae (Myxophyceae = blue-green algae) and Rhodophyceae (red algae) contain large amount of phycobilins, particularly phycocyanins.

​

����(1). Chlorophylls�

• Chlorophylls are fat soluble green pigments
• They are chlorins which absorb blue region and reflect green light
• Chlorophylls are responsible for the green colour of algae and other higher plants.
• Seven different types of chlorophylls are reported in algae. They are:
•  Chlorophyll-a  :  in all groups of algae
•  Chlorophyll-b  :  Chlorophyta (green algae)
• Chlorophyll-c  :  Bacillariophyceae (diatoms)
• Chlorophyll-d  :  Rhodophyceae (red algae)
• Chlorophyll-e  :  Xanthophyceae.
• Chlorophyll-f   :  Recently discovered chlorophyll from stromatolites, possibly produced by Cyanobacteria

​

����(2). Carotenoids:�

• Carotenoids are fat soluble yellow pigments present in almost all algal groups found in close association with chlorophylls.
• They protect chlorophylls from photo-damage (solarization)
• Chemically : tetraterpenoids
• Carotenoids with beta-ionone ring have Vitamin-A like activity
• All carotenoids are strong antioxidants

Yellow colour of egg yolk is due to carotenoids

Two types of carotenoids are found in algae.

(1). Carotenes:

• Carotenes are yellow coloured pigments
•  They are unsaturated fat soluble hydrocarbons, do not contain oxygen
• They absorb blue and green light and transmit yellow and red light e.g. α-carotene, β-carotene, and lycopene

(2). Xanthophylls (carotenols):

• They are oxygen derivatives of carotenes.
• E.g. lutein and zeaxanthin (both are responsible for the yellow colour of egg yolk)

​

�3). Phycobilins:�

• Phycobilins are water soluble pigments always bonded with some water soluble proteins called phycobiliproteins
• They are blue and red in colour
• present in Cyanophyceae and Red algae
• Phycobilins are usually found in organisms living in deep water for the efficient absorption of light
• All phycobilins are strongly fluorescent
• They emit orange or red light after fluorescence.
• Two classes of phycobilins are present in algae.
• i) Hycocyanin and ii) Phycoerythrin

(1). Phycocyanin:�

• Phycocyanin are blue coloured pigments in blue green algae and also present in red algae.
• They absorb green, yellow and red light and transmit blue colour.
• Phycocyanins are the principal pigment of Cyanophyceae. 

​

(2). Phycoerythrin:�

• Phycoerythrin are red coloured pigments
• Phycoerythrin are red algae pigments
• They absorb blue green, green and yellow light and transmit red light.
• Phycoerythrin present abundantly in members of Rhodophyceae (red algae)

Batrachospermum Polysiphonia Red Algae

​

All major algal groups have at least one characteristic Dominant pigment

• Cyanophyceae (blue green algae): c- Phycocyanin
• Chlorophyceae (green algae): Chlorophyll b
• Pheophyceae (brown algae): Fucoxanthin
• Rhodophyceae (red algae): r- Phycoerythrin
• Chlorophyll a is universally present in all algal grous

​

Plastids in algae:

• Except in Cyanophyceae (blue green algae, BGA) pigments in algae are found in membrane bound organelles called plastids
• In BGA, plastids are absent, pigments located at peripheral cytoplasm called chromoplasm
• Plastids are two types:

(1) Leuoplast: – Colourless plastids

(2) Chromoplast: – Coloured plastids

​

Plastid forms in algae�Algae shows great diversity in plastid shape, Plastids may be:�

• Cup shaped: Volvox
• Clamydomonas
• Discoid: Voucheria,

Chara

• Girdle shaped: Ulothrix
• Reticulate: Oedogonium,

Hydrodictyon,

Cladophora

• Spiral: Spirogyra
• Stellate (star shaped): 

Zygnema

​

Spiral Shaped Chloroplast (Spirogyra)

Pyrenoids:

• They are proteinacious bodies present in chromatophoresConsidered as the organelle of synthesis and storage of starch
• In some Chlorophyceae pyrenoids are surrounded by starch grains
• Pyrenoids arise de-novo or by the division of preexisting pyrenoids
• Pyrenoids absent in blue green algae

​

Pyrenoid of Chlamydomonas

Reserved food materials in algae:

• It is also called as food reserve. It is the stored form of food in the cells for energy.
• Different algal groups have different types of reserved food materials.
• Similar to pigmentation in algae, the distributional difference in reserved food is also in the classification of different algal groups.
• Cyanophyceae: cyanophycean starch
• Chlorophyceae: Starch
• Rhodophyceae: Floridean starch
• Phaeophyceae: Laminarin, manitol and oil

​

�Reproduction in algae:�

• Algae reproduce by three methods:

(1)Vegetative reproduction: Cell division, fission, fragmentation, Hormogonia, formation of adventitious branches, tubers, buddings etc. are the important vegetative reproduction methods in algae.

(2) Asexual reproduction: By a variety of motile or non-motile spores. Zoospore, aplanospore, hypnospore, tetraspore, autospore, akinetes etc are the important spore types in algae

(3) Sexual reproduction: here the union of gametes are involved: Autogamy,  hologamy,  isogamy, anisogamy and oogamy are the different types of sexual reproduction algae.

​

(1)Vegetative reproduction:

Cell division and Fission

Tetrabaena socialis Cosmarium Chlorella

Fragmentation Hormogonia

(2) Asexual reproduction

Zoospore , Akinites, Aplanospore, Azygospores

​

Tetraspores, Akinetes & Heterocysts

Sexual reproduction: 

• union of gametes are involved: isogamy, anisogamy and oogamy

Alternation of generation:�

• Alternation of generations (also known as alternation of phases) is a term primarily used to describe the life cycle of plants
• Most algae have an alternation of many celled haploid gametophytic generation with many celled diploid sporophytic generation, which alternate regularly.

​

Life cycle in algae:

• The growth and development consists of a number of distinct morphological and cytological stages
• The sequence of these orderly changes is called life cycle
• Life cycle: sequence of all different phases or events through which an organism passes from zygote (diploid) of one generation to the zygote of the next generation through gametes (haploid)
• There are five types of life cycles in algae based on the number of haploid and diploid generation

​

Life cycle in algae:

• (1) Haplontic: simple type, major stages in the life cycle are haploid, the diploid stage is represented by only the zygote. Zygote undergo meiosis to produce spores (Chlamydomonas, Ulothrix)
• (2) Diplontic: Just reverse of the haplontic type. Major stages in the life cycle are diploid, the haploid stages are represented only by gametes. (Sargassum, Codium)
• (3) Haplobiontic: Three phases in life cycle. Among three phases, two are haploid and one is diploid (Batrachospermum, Coleochaete)
• (4) Diplobiontic: Three phases in life cycle, two are diploid and one is haploid. Majority of marine Red algae are this type (Polysiphonia)

​

Haplontic life cycle:

• Most common type of life cycle in algae
• Life cycle is diphasic (two phases)
• The prominent phase is haploid gametophytic phase
• The diploid (sporophytic) phase in the life cycle is represented by the ZYGOTE
• Zygote is formed by the fusion of haploid male and female gametes
• Zygote immediately undergo meiosis to produce haploid zoospores
• Zoospores germinate and grow by mitosis to produce the haploid gametophytic generation
• Gametophytic plant produce male and female gametes by mitosis
• Haplontic life cycle is the most primitive and simplest type of life cycle
• Other types of life cycles in algae are developed from this type
• Example: Most of the green algae such as Chlamydomonas and Ulothrix

​

(2). Diplontic life cycle�

Ø  This type is just a reversal of the haplontic type of life cycle

Ø  Life cycle is diphasic, but the prominent phase is diploid sporophytic phase

Ø  Haploid gametophytic phase in the life cycle is represented only by gametes

Ø  Here gametes are produced in the gametangia by meiosis

Ø  Moreover zygote do not undergo meiosis, rather it develop into a diploid sporophytic phase by mitosis

Ø  Example: Sargassum, Codium, Bryopsis, Fucus

​

(3). Haplodiplontic life cycle

​

Ø  Life cycle is diphasic

Ø  One phase is haploid gametophyte and the other is diploid sporophyte

Ø  Diploid zygote develop into diploid sporophytic generation

Haplo-diplontic Life Cycle

Ø  Sporophytic plant produce sporangia which produce haploid zoospores by meiosis

Ø  Zoospores develops into haploid gametophytic generation

Ø  Gametophyte produce gametes

Ø  Male and female gametes fuse to form the diploid zygote

Ø  There are two types of haplodiplontic life cycle

(a). Isomorphic: gametophytic and sporophytic plants are morphologically similar (example: Ulva, Chaetophora)

(b). Heteromorphic: gametophytic and sporophytic plants are morphologically dissimilar (Laminaria, Urospora)

​

​

�4. Haplobiontic life cycle:�

Ø  Here the life cycle is triphasic (three phases)

Ø  In this type, there will be three phases in the life cycle, one diploid and two haploid phases

Ø  The three phases are:

(a). Gametophyte phase (n): haploid phase 1

(b). Zygote (2n): diploid phase

(c). Carposporophyte phase (n): haploid phase 2

Ø  Haplobiontic type of life cycle is shown by Nemalionales of Rhodophyceae (Eg.Batrachospermum)

Ø  Gametophytic phase produce haploid gametes

Ø  Male and female games fuse to form the zygote, the only diploid phase in the life cycle

Ø  Zygote undergo reduction division (meiosis) to produce haploid spores which germinate into an intermediate haploid phase called carposporophyte

Ø  Carposporophyte reproduce asexually by carpospores (n).

Ø  Carpospores germinate and develop in to haploid gametophytic generation

​

5. Haplo-diplobiontic life cycle:�

Ø  Most complex and advanced type of life cycle in algae

Ø  Life cycle is triphasic with one haploid phase and two diploid phases

Ø  Among the three phases, two will be diploid and one haploid phase Diplobiontic life cycle is found in all Rhodophycean members except those in the order Nemalionales

Ø  Polysiphonia is the most common example showing haplo-diplobiontic life cycle

Ø  The life cycle of Polysiphonia includes three phases

(a). Carposporophyte – diploid (2n)

(b). Gametophyte – haploid (n)

(c). Tetrasporophyte – diploid (2n)

Ø  Diploid zygote (2n) develop mitotically to diploid carposporophytic phase

Ø  Carposporophyte produce diploid carpospores (2n)

Ø  Carpospore germinate into diploid tetrasporophytic phase

Ø  Tetrasporophyte produce haploid tetraspores by meiosis

Ø  Tetraspore germinate into the haploid gametophytic generation

Ø  Gametophytic generation produce male and female gametes

Ø  Games fuse to form diploid zygote

Ø  Thus in this haplo-diplobiontic life cycle, two diploid phases (carposporophyte and tetrasporophyte) alternate with a haploid gametophytic phase.

​

​

Major Classes of Algae (algal systematics)�

(1) Cyanophyta: Blue green algae (BGA), prokaryotes

(2) Euglenophyta: Motile, protozoan like algae lack true cell wall

(3) Crysophyta: Golden-brown algae = diatoms

(4) Pyrrophyta: Dinoflagellates

(5) Chlorphyta: Green algae

(6) Rhodophyta: Red algae

(7) Paeophyta: Brown algae

​

�Classification of Algae:�

• International Code of Botanical Nomenclature has recommended the following suffices for the different categories of algae
• Division - phyta
• Sub-division - phytina
• Class - phyceae
• Sub-class - phycidae
• Order - ales
• Sub-order - inales
• Family - aceae
• Sub-family - oideae

​

��CLASSIFICATION OF ALGAE �PROPOSED BY SMITH��

• Smith (1933, 1951, 1955) gave classification of algae on the following basis:
• Characters of vegetative cells
• Morphology of motile reproductive cell
• He divided algae into seven divisions, then classes were included in each division.

1.Division Chlorophyta

• Mostly fresh water, a few marine
• Chlorophyll a and b are dominant pigments
• Reserve food is starch
• Motile reproductive cells have two to four flagella which are anteriorly inserted, equal and of whiplash type
• Chlorophyta includes two classes:
• Chlorophyceae
• Charophyceae

​

�2. Division Euglenophyta�

• Plants are fresh water and terrestrial
• Chlorophyll a, b and β carotene are dominant pigments
• Reserve food is paramylum and fats
• Motile cells have one, two or three flagella, anteriorly inserted into a narrow gullet
• Multiplication takes place usually by cell division
• Euglenophyta includes only one class:
• Euglenophyceae

​

EUGLENALES :- EG:- EUGLENA

�4. Division Chrysophyta�

• Most of the plants are fresh water (about 75 %) and rest are marine
• Main pigments are carotene and xanthophylls
• Reserve foods are leucosin and oil
• Cell wall is composed of two over-lapping silicified halves
• Sexual reproduction varies from isogamous to oogamous type
• Chrysophyta includes three classes:
• Chrisophyceae
• Xanthophyceae
• Bacillariophyceae

​

�5. Division Phaeophyta�

• Most plants are marine
• Main pigments are phycophein and fucoxanthin
• Reserve foods are polysaccharide (laminarin) and alcohol (mannitol)
• Cell wall is made up of cellulose, fucinic and alginic acids
• Sexual reproduction varies from isogamous to oogamous type
• Motile reproductive cells are pyriform in shape with two laterally inserted flagella, one of which is whiplash type
• Phaeophyta includes three classes:
• Isogeneratae
• Heterogeneratae
• Cyclosporae

​

​

​

�6. Division Cyanophyta �(Blue green algae)�

• Most fresh water plants, some species are free living, while others grow on larger algae (epiphytic) or within the tissue of other plants (endophytic)
• Cell is prokaryotic
• Main pigments are c-phycocyanin and c-phycoerythrin
• Reserve food is stored in the form of cyanophycean starch
• Cell wall is made up of cellulose, fucinic and alginic acids
• Sexual reproduction is absent; asexual reproduction takes place by hormogonia, fragmentation and akinetes
• Motile cells are absent
• Cyanophyta includes only one class:
• Cyanophyceae or Myxophyceae

​

�7. Division Rhodophyta (Red algae)�

• Mostly marine algaeMain pigments are r-phycoerythrin (due to which this algae is red in colour) and r-phycocyanin
• Plant body is thalloid, non-motile and complex
• Reserve food is stored in the form of floridean starch
• Sexual reproduction is oogamous
• Motile reproductive cells are absent
• Rhodophyta includes only one class:
• Rhodophyceae

​

VOLVOCALES :- EG:- VOLVOX

TETRASPORALES:- EG :- TETRASPORA

ULOTRICHALES :- EG:-ULOTHRIX

ULVALES :- EG:- ULVA

CLADOPHORALES:- EG:- CLADOPHORA

OEDOGONIALES :- EG:- OEDOGONIUM

ZYGNEMATALES :- EG:- ZYGNEMA

CHLOROCOCCALES :- EG:- CHLOROCOCCUM

SIPHONALES :- EG :-VAUCHARIA

SIPHONOCLADIALES :- EG:-VALONIA

�Economic Importance of algae�

• Many algae are used by human beings for food, manufacture iodine in some other purposes from ancient times. Many researches are being done in phycology (study of algae) and many workers are trying to find out the food value of algae, their importance in industries and importance in agriculture. The importance of role played by algae in the world is be coming more appreciated each day because of the increased utilization that many of them are valuable to man. Value is as under.

​

(1) Algae as food:

• Large numbers of Algae are used as source of food by human beings. They are rich in carbohydrates, inorganic substances and vitamins. Vitamins A C D and E are main constituents of these plants.Laminaria species is the important edible seaweed in Japan and the food item 'Kombu' is prepared from it. 'Aonori' from Monostroma; 'AsakusaNori' from Porphyra are prepared in different countries.

• Porphyra has 35% protein, 45% carbohydrates, Vitamins B and C and Niacin.Spirogyra is chief source of food ulva (sea lettuce) is also used be man as food. Nostoc is used as food material in South America. Algae is used to decorate pastries, sandwiches, rice, fish, cakes and jelly cakes in Japan. Agar Agar is also used in preparation of ice-cream and jellies. Another algae Rhodomeniapalmata is chewed like tobacco in Scotland. Hair vegetable is eaten in China and algae Nostoc commune is one of its constituents

​

(2) Algae in industry:

• Algae belonging to Phaeophyceae, like Laminaria, Ecklonia, Eisenia, etc. are used in the industry to prepare Iodine in industries. Phyllophora is used to prepare Iodine in Russia. Iodine industry is mainly depended upon algae.

​

• Agar-Agar obtained from algae like Geliduim is used as sizing of textiles. Algae chondrius and careragaenium which yields a mucilage is used in manufacture of left hats as stiffening agent. It has the properties of agar and therefore used as ingredient of cosmetics, shaving creams, shoe polishes and shampoos. Various red algae like lamineria yields Iodine. Several sea weeds also yield bromine, acetic acid, formic acid and acetone.

​

• Diatoms (an algae) prepare diatomaceous earth and is extensively used in sugar refineries and soap manufacture. It is also helpful in cement industry, in the manufacture of dynamite, rubber and blotting paper. It is also used in isolation of boilers, blast furnaces and at various other places where very high temperature (1000°C) is required.Algin is extracted by boiling algae I washing soda solution and rollers of type writers are prepared from it. Japanese prepare artificial wool from sargassum.

​

(3) Fodder for cattle:

•  Rhodymenia palmate is used as food for sheeps in Narvey.
• Laminaria saccharina, Pelvitia, Ascophyllum, etc. species are used as food for cattles. 

�

(4) Algae in Agriculture:

• Presence of mucilage in most of the members of Myxophyceae helps in development and better nourishment for nitrogen fixing bacteria. Some of them like Anebena, Nostoc etc are able to utilize and fix atmospheric nitrogen, thus increasing soil fertility. Some members of myxophyceae were able to fix 20 Lbs. of atmospheric nitrogen per acre in rice field.

​

(5) Algae in Pisi culture

• Sea algae are used as food for fishes. So they play an important role in Pisi culture. Some green-algae, Diatoms, some blue-green algae are used as food material to fishes. These are also making the water clean, by realizing Oxygen. 

​

(6) Algae in Biological research

• Photosynthesis and metabolism are based on studies of unicellular algae such as chlorella. Certain algae like chlamydomonas are being used in genetical studies. Chlamydomonas was the first haploid organism on which successful hydridization was accomplished.Certain algae like Acetabularia, Valonia and Nitella show great success in studies on morphogenesis, nuclear function, nuclear cytoplasmic relationship and ionic exchange with the environment.

​

(8) Alginates

• These are the salts of alginic acid found in the cell wall of phaeophyceae. Alginates are extracted from Fucus, Laminaria, Macrocystis and Ecklonia. Alginates are used in the preparation of flame-proof fibrics, plastics, paints, gauze material in surgical dressing, soups, ice creams etc. 

9. Agar-Agar

• Agar-agar is a jelly like substance of great economic value. It is obtained from certain red algae like Gelidium, Graciliaria, and Gigartina. Agar is used as a culture medium for growing callus in tissue culture.
• From above discussion it is clear that algae are great importance for human being.

​

Nostoc Balls

Nostoc Filament: Trichome

Hormogonia

Life Cycle of Nostoc

Spirogyra

Classification

• Kingdom :Plantae
• Sub-Kingdom: Cryptogams
• Division :Chlorophyta
• Class :Chlorophyceae
• Order :Zygnematales
• Family :Zygnemataceae
• Genus :Spirogyra