Symbiosis Involving Fungi

Two types involving fungi:
     1) mutualism - both species benefit
     2) parasitism - one benefits, one harmed

Mutualism
     Two examples: mycorrhizae & lichens

Mycorrhizae are the result of fungi in the roots of vascular plants
     Fungus benefits: obtains photosynthates (esp.: sugar)
     Plant benefits: obtains minerals (esp.: N, P)

Two types of mycorrhizae based on type of infection

1) Ectomycorhhizae (sheathing)

• Grow between root cells of epidermis & cortex, not into cells, not beyond endodermis
  results in short, stubby roots
  most common in: conifers, oaks, willows which are infected with basidiomycetes.

2) Endomycorhhizae (internal)

          Fungal hyphae grow into root cells
          Within cell walls, NOT cell membrane
          Mainly in epidermal & cortex cells
          Most common in angiosperms (ex.: tulip tree) which are infected by zygomycetes

Lichens are the result of a fungus and an algae living together

• a) The mycobiont - a fungus

  Mostly ascomycetes, but some basidiomycetes

  Provides a suitable environment & minerals to algae

• b) The photobiont - an algae

  An algae (green) or cyanobacterium

  Provide carbohydrate & nitrogen compounds to fungus

symbiosis allows for them to live in very harsh environments: rock surfaces, tree trunks

 

Ability to survive related to ability to dehydrate quickly

Fungal surface blocks UV light

Algae

Algae are photoautotrophic, unicellular (colony) as well as multicellular (filamentous). Cell walls are made of cellulose or pectin, and require high moisture for their growth. Reproduction is through sexual as well as asexual.

Five phyla

1. Brown algae

They are dark pigment producing, non motile multicellular organism, contains chlorophyll a and b. Example. Sea weed.

2. Red alage

They are red pigment producing, non motile multicellular organism, contains chlorophyll a and d. Example - Sea weed.

3. Green Algae

They are filamentous unicellular as well as multicellular organisms, contains chlorophyll a and b.

Example- Pond scum

4. Diatoms

They are light brown pigment producing unicellular organisms. Cell wall is made of pectin and silicon oxide.

5.Dinoflagellates

They are unicellular, flagellated organisms. Their cellulose walls are interlocked. Example- Plankton, red tide