Classification of Chlorophyceae (Green Algae)

Classification of Chlorophyceae (Green Algae)

Classification of Chlorophyceae or Chlorophyta (Green Algae):
Classification of Chlorophyceae or Chlorophyta (Green Algae):

 

The class Chlorophyceae divided into following orders:

Order. 1. Volvocales:(Chlorophyceae)

The order Volvocales includes 60 genera and about 500 species.

Important characteristics:

  1. They are commonly found in fresh water bodies. Some are grown in brackish water, marine water and also on soil surface.
  2. The plant body or thallus is unicellular or multicellular(many celled) and the multicellular ones are colonial in habit.
  3. Both unicellular and colonial members are motile(Having flgella), either throughout or some part of their life cycles.
  4. They reproduce both sexually and asexually. Asexual reproduction takes place by zoospo­res, aplanospores, hypnospores etc. and sex­ual reproduction is takes place by isogamy, anisogamy and oogamy.

Classification:

Fritsch (1935) divided the order Volvocales into 3 suborders and 7 families.

Order. Volvocales:

  1. Sub order. Chlamydomonadineae
  2. Sub order. Tetrasporineae
  3. Sub order. Chlorodendrineae

Order. 2. Ulotrichales(Chlorophyceae)

Order Ulotricales includes 80 genera and about 430 species. Most of them are found in fresh water, while a few are marine (e.g., Ulva).

Classification of Chlorophyceae (Green Algae)

Important characteristics:

  1. They are commonly found in fresh water bodies(e.g., Ulothrix) or on soil, but a few are marine (e.g., Ulva, Enteromorpha).
  2. Plant body is commonly  unbranched fila­ment like ; but in Ulvaceae it is parenchymatous or foliaceous.
  3. Cells are uninucleate(single nucleus) and contain different types of chloro­plast  like C-shaped, pari­etal, axial etc.
  4. Each chloroplast contains/have one or more pyrenoids.
  5. Asexual reproduction takes place by means of biflagellate zoospores or quadriflagellate zoospores, aplanospore and akinetes.
  6. Sexual reproduction takes place by gametic union and may be isogamous, anisogamous, or oogamous type.

Classification:

Fritsch (1935) divided the order Ulotrichales into 3 suborders and 6 families.

Order. Ulotrichales

Sub order. Ulotrichineae

Family. Ulotrichaceae

  • Microsporaceae
  • Cylindrocapsaceae
  • Ulvaceae
Sub order. Prasiolineae

Family. Prasiolaceae

Sub order. Sphaeropleineae

Family . Sphaeropleaceae

Family. Ulotrichaceae

Important characteristics of Ulotrichaceae
  1. The plant body is an unbranched filament like.
  2. Cells of the filament are uninucleate(One Nucleus).
  3. Cells have single girdle-shaped, parietal chloroplasts.
  4. Sexual reproduction is isogamous and takes place by the union of biflagellated gametes

Order. 3. Chaetophorales: Chlorophyceae

Chaetophorales are the plants with hair or setae.

Important characteristics:

  1. Members of Chaetophorales are generally found in fresh water.
  2. Plant body is filamentous and shows promi­nent heterotrichous(prostrate  +Erect system) habit ; however, in Coleochaete, the prostrate system(creeping) is well- developed and in Microthamnion the erect system is well-developed.
  3. Some members have setae (Coleochaete) or hairs (Stigeoclonium) of different types. The hairs may be in the form of single elon­gated cell or rows of fine and elongated cells.
  4. The cells contain a parietal shaped chloroplast with many pyrenoids (starch containing bodies).
  5. Erect system bears/contain reproductive structures.
  6. Vegetative reproduction takes place/done by frag­mentation.
  7. Asexual reproduction takes place by biflagellate zoospores or quadriflagellate zoospores, aplanospores or akinetes.
  8. Sexual reproduction is commonly isogamous (Fritschiella, Stigeoclonium), anisogamy (Aphanochaete) and oogamy (Coleochaete) are found occasionally/Rarely.

Fritsch (1935) classified this order into 5 families.

These are:

Chaetophoraceae, Trentepohliaceae, Coleochaetaceae, Chaetosphaeridiaceae and Pleurococcaceae.

Family. Coleochaetaceae:

Important characteristics:
  1. Plant bodies possess a typical heterotrichous(erect + prostrate) habit. Generally the projecting(upward) system is dominant and looks like disc.
  2. Cells are uninucleate(one Nucleus) with single lamellate parietal chloroplast with one or two pyrenoids(Starch containing bodies).
  3. All or some cells bear/haing/containing a single long sheathed bristle or seta.
  4. The sheath is present in the form of a basal cylinder of mucilage layer.
  5. The growth is always take place through the apical region.
  6. Asexual reproduction takes place by means of biflagellated zoospores.
  7. Sexual reproduction is oogamous type.

Order. 4. Oedogoniales. Chlorophyceae

Important characteristics:

  1. Most of the members grow in fresh water. The order is represented by only three genera, Oedogomium, Oedocladium and Bulbochaete.
  2. They are filamentous and the filaments may be branched (Oedocladium and Bulbo­chaete) or unbranched (Oedogomium).
  3. The plant body is differentiated into apical and basal region.
  4. It consists of cylindrical cells and the cells are longer than breadth.
  5. Cells are uninucleate and have reticulate chloroplast with pyrenoids.
  6. Cell division is elaborate and a cap is formed at the upper end of the daughter cell.
  7. Asexual reproduction takes place by pyri- form, multinucleate and multiflagellate zoospores. Flagella are arranged in a ring around the beak-like anterior end.
  8. Sexual reproduction is advanced oogamous type.
  9. Both androspores and antherozoides are multiflagellate.Chlorophyceae
  10. Male gametes are similar to zoospore but smaller in size.
  11. Heterothallic or dioecious species are of two types: macrandrous (where male and female filaments are of normal size) and nannandrous type (where male is very small i.e., dwarf male or nannandrium and the female one is of normal size).Chlorophyceae

Classification:

According to Fritsch (1935) the order Oedogoniales contains only one family Oedogoniaceae. The family has only three genera: Oedogomium, Oedocladium and Bulbochaete.

Order.5. Siphonales:

Important characteristics:

  1. Most of the members of Siphonales are marine. A few members are freshwater. Some members grow as epiphytes or endophytes.
  2. Thalloid plant body is variously branched, aseptate and multinucleate i.e., coenocytic.
  3. Plant body may be simple vesicular type (Protosiphon) to much branched filamentous type.
  4. Numerous small and discoid chromato- phores are arranged peripherally inside the thallus.
  5. Nuclei are present towards the inner layer.
  6. The characteristic pigments of this order are siphonin and siphonoxanthin.Chlorophyceae
  7. Presence of siphon-like central vacuole throughout the plant body, which remains filled with sap. Cytoplasm is present between the outer wall and vacuole. The order is named “Siphonales” because of the presence of siphon-like vacuole.
  8. The plant reproduces by all the three means vegetative, asexual and sexual. Vegetative reproduction takes place by fragmentation, asexual reproduction by multiflagellate zoospore, aplanospore or hypnospore and sexual reproduction by oogamy. Rarely they perform iso- and anisogamy.Chlorophyceae

Classification:

Fritsch (1935) divided the order Siphonales into 9 families.

These are:

  1. Protosiphonaceae
  2. Caulerpaceae
  3. Dasycladaceae
  4. Derbesiaceae
  5. Codiaceae
  6. Valoniaceae
  7. Chaetosiphonaceae
  8. Phyllosiphonaceae
  9. Vaucheriaceae.

This classification is also followed by M. O. P. lyenger (1951)

Order.6. Charales 

Important characteristics:

  1. Members of this order are distributed throughout the world.
  2. Commonly they are found in fresh water with muddy or sandy bottom and also in water flowing over limestone.
  3. Plants are macroscopic, much branched, and erect and commonly up to 30 cm in length.
  4. The plants are differentiated into nodes and internodes. Some of the nodes bear bran­ches of unlimited growth, those are again divided into nodes and internodes. Each node of the main axis and branch of unlimi­ted growth bear a number of branches of limited growth.
  5. Cells are very long, uninucleate and contain many discoid chloroplasts.
  6. Most of the species show cortication in the internodes. The cortex consists of vertically elongated row of cells.
  7. Sexual reproduction is highly advanced, oogamous type.
  8. The male and female reproductive bodies are globule and nucule,respectively. Globule develops many antherozoids and nucule contains only one egg.Chlorophyceae
  9. Zygote is produced after sexual reproduc­tion. It shows very much elaborate post- fertilization changes. During germination, zygote undergoes meiosis and gradually it forms the plant body.Chlorophyceae

Classification:

Fritsch (1935) placed the order Charales under the class Chlorophyceae includes only one family the Characeae having 2 sub families: 1. Nitelleae and 2. Chareae.

Bold and Wynne (1978) placed the order Charales alone under the only class Charophyceae, under the division Charophyta. The order Charales includes only one family Characeae.Divn. Charophyta: Class. Charophyceae.

  1. C. Bold and M. J. Wynne (1978) in their classification took out Chara along with some other genera like Tolypella, Nitella, Nitellopsis, Protochara, Lamprothamnium and Lychnotham- nus from Chlorophyceae and placed them in a separate Division Charophyta. The Charophyta consists of single class Charophyceae; order Charales and family Characeae.Chlorophyceae
Important characteristics of Characeae:
  1. The division Charophyta includes the members of green algae, commonly known as stoneworts.
  2. Plant body shows much elaboration of vegetative structures encrusted with calcium carbonate.
  3. Plant body is erect and consists of elon­gated, jointed, commonly green main axis bearing branches, differentiated into nodes and internodes.
  4. Each node bears a whorl of lateral branchlets.
  5. Asexual reproduction is absent.
  6. Sexual reproduction is of oogamous type.
  7. Antheridia (globule) and oogonia (nucule) show more complexity and elaboration than other Chlorophycean members.Chlorophyceae
  8. Motile cells are asymmetrical and two flagella are attached in lateral position of an antherozoid.
  9. Sex organs are so large that they can be visible with naked eye.
  10. Zygote on germination forms proto- nema (Chara, Nitella) from which vege­tative plants are developed.

.Order.7. Chlorococcales:

  1. Unicellular or colonial,
  2. non-motile in the vegetative condition,
  3. reproduced by zoospores or aplanospore;
  4. almost exclusive fresh water.Chlorophyceae

Examples:

  • Hydrodictyon
  • Pediastrum, etc.

Order.8. Cladophorales:

  1. Simple or branched,
  2. filamentous with cells containing two to many nuclei and usually with elaborate large chloroplasts;
  3. mostly isogamous;
  4. freshwater and marine.

Exam­ple:

  • Cladophora.

Order.9. Conjugales:

  1. Mostly are Unicellular or colonial (generally filamen­tous) with elaborate chloroplasts;
  2. They Have motile gametes ;
  3. Re­production is take palce by vegetative cell division or by conjugation of amoeboid gametes;
  4. exclusively freshwater.Chlorophyceae

Examples:

  • Spirogyra,
  • Zygnema,
  • Cosmarium,
  • Closterium,

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