Algae: An Introduction

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Phycology or algology is the study of the algae. The word ‘Phycology’ is derived from the Greek word ‘Phykos’ meaning seaweed.

The algae are thallophytes (plants lacking roots, stems and leaves) that have chlorophyll as their primary photosynthetic pigment and lack a sterile covering of cells around their reproductive cells or organs.

General Characteristics

Nature, Habit and Habitat

  • Algae are cosmopoliton in distribution. They may grow in all kinds of habitats.
  • The group Algae is a heterogenous group. So, thallus organization varies in a great range. For example:
    -Motile unicellular: Chlamydomonas.
    -Motile colonial: Volvox.
    -Filamentous: Spirogyra.
    -Heterotrichous: Fritschiella.
    -Siphonaceous: Vaucheria.
  • Plant body is not divided into roots, stems and leaves.

Cellular characteristics

  • They may be prokaryotic or eukaryotic. Prokaryotics are included in Cyanobacteria.
  • They are autotrophs as they have chlorophyll.
  • Each cell is bounded by a typical cell wall, with a few exceptions like Euglena and Gymnodinium where a cytoplasmic membrane (made up of a protein layer supported by a substructure of microtubules), called pellicle is present.
  • Vascular bundle is absent.

Reproductive & Growth characteristics

  • Growth is either generalized (e.g. Ulva) or localized (e.g. Cladophora).
  • Reproduction takes place by all three means: vegetative, asexual and sexual.
  • Generally sterile jacket layer is absent (Exception: Chara).
  • Every cell has reproductive power which is unique.
  • No embryo formation is seen in algal members.

Resemblance with Fungi

Algae show the following resemblance with fungi:

  • The plant body is thalloid in both.
  • Sex organs are simple and non-jacketed.
  • There is no embryo formation after fertilization.

Source:

  1. Textbook of Algae by O P Sharma.