What are the characteristics of green algae?
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What are the characteristics of green algae?
Aug 09, 2022, 16:45 IST
The characteristics of green algae?
CHLOROPHYCEAE: GREEN ALGAE
About 90% of the total species grow in fresh water habitats and 10% are marine. They are cosmopolitan in distribution. They may be
• Terrestrial- growing on moist soil, walls and rocks, e.g., Fritschiella.
• Epiphytes- growing on other plants, e.g., Trenteopohlia, Protococcus, etc.
• Endophytes- growing inside the other plants, e.g., Coleocheate nitellum inside the thallus of Nitella.
• Epizoic- growing on the surface of animals, e.g., Cladophora and Charaeilum on mollusc shells and crustaceans, respectively.
• Endozoic- living inside body of animals, e.g., Zoochlorella inside sponges, C’hlorella in the body of Hydra.
• Cryophytes growing in the polar region on ice and snow, e.g., Chlamydomonas nivalis,
• Ilaematococcus nivalis (causing red snow ball).
• Thermophilic- growing in hot springs, e.g., Chlorella sp.
• Parasitic- growing as pathogens and causing diseases, e.g., Cephaleuros (causing red rust disease of tea and coffee).
• Symbionts - as components of certain lichens.
• Thallus is of various types: unicellular flagellate (e.g. Chlamydomonas), unicellular non flagellate (e.g., Chlorella) flagellate colonies, (e.g., Volvox) unbranched filamentous (e.g., ulothrix), simple branched (e.g., Cladophora), heterotrichous with prostrate and vertical branches, (e.g., Draparnaldia), and parenchymatous (e.g., Ulva).
• Cell wall contains cellulose with a few exceptions.
• Photosynthetic pigments are similar to those of higher plants: chlorophyll a, chlorophyll b, carotenes and xanthopylls.
• Food reserve is Starch.
• Chloroplasts generally contain pyrenoids for storage of starch.
• Vegetative reproduction occurs by fragmentation, stolons and tubers.
• Asexual reproduction takes place by mitospores. The common asexual spores are zoospores, aplanospores, hypnospores, akinetes, etc.
• Sexual reproduction is effected by isogamy, anisogamy and oogamy.
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Three types of life cycle occur in green algae: haplontic, diplontic and diplohaplontic.
• In haplontic life cycle the dominant phase is haploid. The diploid stage is present only in the form of zygote or zygospore. Meiosis occurs at the time of its germination of zygote (zygotic meiosis, e.g., Ulothrix, Spirogyra and Chlamydomonas).
• In diplontic life cycle, the dominant phase of the alga is diploid. It gives rise to haploid gametes through meiosis (gametic meiosis, e.g., Caulerpa). The gametes fuse and the fusion product or zygote regenerates the diploid phase.
• The haplodiplontic life cycle possesse well developed multicellular haploid and diploid structures. The haploid gametophyte gives rise to haploid gametes. The fusion product of gametes or diploid zygote grows directly into diploid sporophyte. The sporophyte produces haploid spores through meiosis (sporic meiosis, e.g., Ulva. Cladophora). Meiospores germinate into new gametophytes.
What are the characteristics of green algae? pdf
