FUNGI

FUNGI LIVE BY ABSORPTIVE HETEROTROPHY

Fungi are opisthokonts with absorptive heterotrophy and with chitin in their walls. Yeasts are unicellular, free-living fungi.

The body of a multicellular fungus is a mycelium- a network of filaments called hyphae. Hyphae may be septate or coenocytic.

SEPTATE:

• Lacking septa to divide cells.
• A septum is a wall, dividing a structure
• into smaller ones.

COENOCYTIC:

• A multinucleate cell which can result from
• multiple nuclear divisions without
• accompanying cytokinesis.

Fungi are often tolerant of hypertonic environments, and many are tolerant of extreme temperatures.

NUTRITIONAL MODES

Saprobic fungi, as decomposers, make crucial contributions to the recycling of elements, especially carbon.

Many fungi are parasites of plants, harvesting nutrients from plant cells by means of haustoria.

HAUSTORIA

• The portion of the parasitic fungus that
• penetrates the host's tissue and draws
• nutrients from it.

Certain fungi have relationships with other organisms that are both symbiotic and mutualistic.

Some fungi form lichens, which live on exposed surfaces of rocks, trees, and soil.

Mycorrhizae are mutualistic associations of fungi with plant roots. They improve a plant's ability to take up nutrients and water.

Endophytic fungi live within plants and may provide protection to their hosts from herbivores and pathogens.

MAJOR GROUPS OF FUNGI

Many species of fungi reproduce both sexually and asexually. In many fungi, sexual reproduction occurs between individuals of different mating types.

The microsporidia are highly reduced unicellular fungi. They affect several animal groups.

The three distinct lineages of chytrids all have flagellated gametes.

In the sexual reproduction of terrestrial fungi, hyphae fuse, allowing gamete nuclei to be transferred.

Zygospore fungi have a resting stage with many diploid nuclei. Fruiting structures are simple stalked sporangiophores.

In sac fungi and club fungi, a mycelium containing two genetically different haploid nuclei, called a dikaryon, is formed. This condition is unique to the fungi.

Sac fungi have septate hyphae; their sexual reproductive structures called ascomata.

Club fungi have septate hyphae. The most familiar type of plant pathogen is the mushroom forming species. Their fruiting structures are called basidiomata and sexual structures are called basidia.

FUNGI CAN BE SENSITIVE

The diversity of lichen growth on trees provide sensitive indications of air quality.

Museum collections of fungi provide a historical record of atmospheric pollutants that were present when the fungi were growing.

Reforestation projects require restoration of the mycorrhizal fungal community.