Monday, July 9, 2018

Algae [Plant kingdom]

ALGAE

  • M.O.P. Iyengar[1886-1963] was born in Madras.
  • He started his Research in phycology especially about volvocales.
  • The great algologist Fritsch was the guide of M.O.P. lyengar for algal studies at London.
  • Term "Algae" was given by Linnaeus.
  • Phycology - Study of algae.
  • Father of Phycologoy - Fritsch  Book  "Structure & Reproduction of algae"
  • Algae are found in both and marine water.
  • Algae are found in many forms like filamentous, colonial.
  • Algae are surrounded by mucilaginous sheath and below the sheath cell wall is present which is made up of cellulose and pectin but mainly made up of cellulose, galactans mannans and minerals like calcium carbonate.
  • On the basis of structure, algae are thalloid i.e. plant body is not differentiated into root, stem and leaves. vascular and mechanical tissue system is also in algae.
  • On the basis of nutrition,algae are photo-autotrophic. They have chloroplast in which photosynthetic pigments are present. classification of algae is mainly based on pigments. Ch-a, carotene are universal pigments of algae.
  • Life cycle is mainly haplontic due to zygotic meiosis.

Reproduction

1. Vegetative  reproduction  

  • Binary fission - Cell is divided into two parts and nucleus is also divided into two parts by mitosis. eg . Found only in unicellular algae 
  • Fragmentation - Filaments break down into small pieces & form new filaments. eg. All filamentous algae.

2. Asexual reproduction  :

It is a common method of  reproduction. 

3. Sexual reproduction :

  • Male sex organ is called antheridium and female is called oogonium. The sex organs of algae are unicellular  & jacketless. But exceptionally sex organs of  green algae Chara (Chara - green algae - known as stone wort ) are muticellular and jacketed.
  • The male sex organ of chara is known as  globule  and female is known as  nucule.
  • plant body of algae is haploid so sexual reproduction take place through zygotic meiosis. So their life cycle is  haplontic. But exceptionally brown algae are diploid so that sexual reproduction take place through gametic meiosis in them. so their life cycle is diplohaplontic
  • Algae reproduce by zygotic meiosis i.e. first division in zygote is meiosis so embryo is not formed.

Sexual Reproduction is of three Types

  • (a)    Isogamous          -    Chlamydomonas debaryabnum, Ulothrix, Ectocarpus 
  • (b)    Anisogamous     -     Chlamydomonas braunii 
  • (c)    Oogamous         -     Chlamydomonas  coccifera, Sargassum, Volvox.