fungi:general character and structure

fungi:

•   Fungi are a large group of achlorophyllus organisms.
•  Study of fungi is called as ‘mycology’ and scientist concerned with fungi called as‘mycologists’
•     it is non-green , nucleated plant body.
• *      Habitat: it grows almost everywhere on earth, where dead or living organic material is present. 

• General characters and introduction to fungi:

• ·   They lacks chlorophyll so cannot make their own food, so they are “heterotrophs”.

  ·      They cannot ingest solid food but can absorb through cell membrane as saprophytes or parasites.
• a)  Saprophytic fungi: which grows where dead organic matter abounds in the substiatum.
  b) Parasite: which live in or on the living bodies of other living organisms and obtain food from them.
  §  Parasitic fungi may cause harm to the host on which it is surviving which is called as disease.
  §  Ectoparasite: - thallus of parasitic fungus may grow on the external surface of the host.
  §  Endoparasite: - where thallus of fungi grows in the tissue of the host plant.
  §  Obligate parasite: - which can grow only upon suitable living host tissues.eg: downy and powdery mildews.
  §  Few fungi also develop symbiotic reaction with green or blue-green algae and form lichens.
  §  Another example is mycorrhiza, where fungus establishes a relationship with the roots of certain higher plants. e.g.: pinus roots and fungal hyphae. Where hyphae performs as a root hair and helps in absorption of water and minerals from soil. While tree provides food and shelter for fungus.
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• Habit or structure of fungi
• a.  Thallus
                          i.               Unicellular thallus- in some lower fungi, thallus is more or less a spherical, single-celled structure. e.g. yeast cell.
                       ii.               Filamentous thallus- majority of fungi are filamentous
  ·      After germination of spore, it give rise to a fluffy thallus consisting of a cottony mass of branched or unbranched filaments called as hyphae.
  ·      Hyphae are usually colorless and embedded in substratum. Hyphae or mycelia can be multinucleated, colorless, septate or aseptate.
  ·      Hyphae comprise the vegetative body of a fungus, called as mycelium. So, hyphae are a structural unit of a mycelium.
  ·      If mycelium is aseptate, multinucleated called as coenocytic. Septate mycelium develop internal cross walls called the septa, which divide the hyphae into segments.
  ·      It can be uni or multinucleated.
  ·      Septa can be oblique, longitudinal, or transverse.
  Ø P.A. micheli (1679-1737) is referred as “father of mycology”, who published book named “Nova plantarum genera”.
  Ø Sir E.J. Butler put the firm foundation of mycology and plant pathology in India. He authored a classic book “fungi and disease in plants”. He is referred as “father of Indian mycology”.

  *      Structure of the fungal cell:

  §  It consists of strong, rigid cell wall enclosing protoplast.
  §  Cell wall is made up of chitin which is also called as “fungal cellulose” because it is different from insect chitin ( polysaccharide based on ‘N’ contain sugar.)
  §  In lower fungi, some flagellated oomycetes consist of ‘cellulosic wall’.
  §  Chitin wall of fungi is permeable both to water and substance in true solution.
  §  Protoplasm which lacks chloroplast, but other than that it consist of cell membrane, vacuole, cell organelles and oue or more nuclei.
  §  All fungi group lacks motile cells in the life cycle. Except some lower fungi where they possess whip-like threads known as flagella.
  “ Aggregation & modification of the hyphae”.
  §  Fungal hyphae are interwoven loosely to form mycelium.
  §  Aggregation of mycelium in different ways makes mycelium.
  
  
  1.  Plectenchyma /Prosenchyma
                        \Pseudo parenchyma
  a)  Prosenchyma- Run more or less parallel to one another & composed of elongated cells.
  b) Pseudo parenchyma- Hyphae gets fused & lose their individuality and forms isodiametric oval cells.
  2.  Rhizomorph-  thick strand or root like aggregation of somatic hyphae is called rhizomorph.
  3.  Other than that other structures like sclerotic, stomata, haustoria etc. forms in different fungi.