Name: KEY

Quiz Two

1. Are fungi which rely on forcible discharge to their spores likely to be further dispersed than those that rely on passive release. Explain your answer (2 pts)

Passive Release. Those that rely on forcible discharge are often only shot a short distance, while those that rely on passive release are usually dry spores that travel long distances in air currents. An example of forcibly discharged fungi, are the coprophilous fungi that are shot beyond the ring of repugnance in order to land on nearby vegetation for ingestion by herbivores. Most cosmopolitan fungi (ie Aspergillus, Penicillium or Rhizopus) are passively released. [An exception are the basidiospores of the mushrooms which may travel a long distance. They are forcibly discharged to get them between the gills and then dispersed by air currents.

2. What is the difference between constitutive and exogenous dormancy? What is required to break each type of dormancy? (2pts)

Dormancy is a period of rest or minimal metabolic activity. Constitutive dormancy is when internal (or innate) properties of the spore impose dormancy and it requires a “trigger” for the breaking of dormancy. Triggers we discussed include heat shock, cold, and some chemicals.

Exogenous dormancy is dormancy imposed by unfavorable environmental (external) conditions. Exogenous dormancy is broken when favorable conditions for growth return. Those conditions must remain present for growth to continue.

3. For true slime molds, which stage(s) have cell walls and which stage(s) lack cell walls? (0.5 points for each stage) What is the nuclear content of each of these stages? (0.5 points for each correct answer)

Cell walls: microsclerotia (n), sclerotia (macrosclerotia) (2n), spores (n), sporangia (2n)

No cell wall: myxamoebae (n), swarm cells (n), plasmodium stage (2n).

4. Describe the differences between a plasmodium and a pseudoplasmodium? (2 points)

Both structures lack cell walls and have a “slimy” appearance because of this. A plasmodium is a multinuclear, acellular (single large cell is acceptable answer) feeding stage of the Myxomycota. The nuclei in the plasmodium are diploid.

A pseudoplasmodium is a multicellular uninucleate structure of the Cellular slime molds composed of aggregated haploid amoebae. It is not a feeding stage.

Plasmodium Pseudoplasmodium

Diploid nuclei haploid nuclei

Feeding (assimilative) not feeding

Acellular multicellular

5. Name a phylum that has a plasmodium stage and one that has a pseudoplasmodium stage. (1 point each)

Plasmodium: Myxomycota, Plasmodiophoromycota

Pseudoplasmodium: Dictyosteliomycota, Acrasiomycota