Exam 31: Fungi

You are a forester charged with increasing productivity in a South American forest newly planted with pines from Oregon.You believe that the southern forest lacks the fungal diversity needed by the North American pines,and that this lack of fungi is affecting the pines' productivity,but you have no evidence to support your ideas.To count how many fungal species were present in the Oregon forest,which methodology would you choose,and why?

Looking at Figure 31.1,draw a new graph that plots the percentage of plant species in the fossil pollen and spore record,and write a figure legend comparing it to the original figure.

The fungi that we commonly know as mushrooms produce which of the following reproductive structures?

Which of the following is an important role for fungi in the carbon cycle?

If seedlings in the shade commonly do receive sugars from plants in the sunlight,which of the following areas should be investigated by future research? Explain why you think each area should (or should not)be investigated? Issues to consider: (1)Plausibility-can the research be performed with current technologies? (2)Is it an interesting question that will lead to valuable future knowledge? If so,describe why the information will be helpful. A.The above-described exchanges were all among seedlings of the same age.Is the rate or degree of carbon transfer from one plant to another more affected by the degree of shading,or by the relative photosynthetic ability (size/age of the tree)? B.Does the identity of the partners matter for rate or degree of carbon transfer? Is there a greater exchange among trees of the same species compared to trees of different species? Or do different fungal species have different capacities for transfer? C.How far (linear distance in meters)can carbon be transferred in nature? Do exchanges occur only between adjacent plants,or can sugars be taken up by plants outside the immediate neighbors? Does distance affect the rate/degree of exchange in and of itself? (Can a heavily shaded tree that is farther away receive more carbon than a nearby tree in the sun?) D.All of these areas should be investigated.

Some fungal species can kill herbivores while feeding off of sugars from its plant host.What type of relationship does this fungus have with its host?

Simard et al.(1997)further hypothesized that if reciprocal transfer did occur,it would be a source-sink relationship driven by photosynthetic rates.That is,if one seedling is in full sun and the other in deep shade,there will be a net movement of carbon from the seedling in full sun to the one in deep shade.If a shade was placed over the birch seedlings and the cedar,and the Douglas fir was left in full sun,what result could Simard and colleagues expect?

There is much discussion in the media about protecting biodiversity, but does it really matter? Canadian and Swiss researchers wanted to know if the diversity of arbuscular mycorrhizal fungi (AMF)was important to the productivity of grasslands (M.G.A. van der Heijden, J. N. Klironomos, M. Ursic, P. Moutoglis, R. Streitwolf-Engel, T. Boler, A. Wiemken, and I. R. Sanders. 1998. Mycorrhizal fungal diversity determines plant biodiversity, ecosystem variability and productivity. Nature 396:69-72). Specifically, they wanted to know if it mattered which specific AMF species were present, or just that some type of AMF was present. They grew various plants in combination with one of four AMF species, no AMF, or all four AMF species together; and they measured plant growth under each set of conditions. All plant species were grown in each plot, so they always competed with each other with the only difference being which AMF species were present. Use the graphs in Figure 31.4 to answer the questions that follow. Note that the x-axis labels indicate the number and identity of AMF species (bar 0 = no fungi; bars A-D = individual AMF species; bar A+B+C+D = all AMF species together). The y-axis indicates the amount (grams)of plant biomass for the species shown in italics above each graph. Figure 31.4 -Based on the van der Heijden et al.(1998)graphs in Figure 31.4,which of the following is the best description of the data supporting the idea that a plant species did not form mycorrhizae with a fungus?

Suzanne Simard and colleagues knew that the same mycorrhizal fungal species could colonize multiple types of trees. They wondered if the same fungal individual would colonize different trees, forming an underground network that potentially could transport carbon and nutrients from one tree to another (S. Simard et al. 1997. Net transfer of carbon between mycorrhizal tree species in the field. Nature 388:579-82). Figure 31.2 illustrates the team's experimental setup. Pots containing seedlings of three different tree species were set up and grown under natural conditions for three years; two of the three species formed ectomycorrhizae (Douglas fir, birch)and the other (cedar)formed arbuscular mycorrhizae. For the experiment, the researchers placed airtight bags over the Douglas fir and birch seedlings; into each bag, they injected either carbon dioxide made from carbon-13 or carbon-14 (¹³CO₂ and ¹⁴CO₂, isotopes of carbon). As the seedlings photosynthesized, the radioactive carbon dioxide was converted into radioactively labeled sugars that could be tracked and measured by the researchers. Figure 31.2 -Refer to Figure 31.2.Which of the following results would support Simard et al.'s (1997)hypothesis that fungi can move carbon from one plant to another? Hypothesis: Sugars made by one plant during photosynthesis can travel through a mycorrhizal fungus and be incorporated into the tissues of another plant.

There is much discussion in the media about protecting biodiversity, but does it really matter? Canadian and Swiss researchers wanted to know if the diversity of arbuscular mycorrhizal fungi (AMF)was important to the productivity of grasslands (M.G.A. van der Heijden, J. N. Klironomos, M. Ursic, P. Moutoglis, R. Streitwolf-Engel, T. Boler, A. Wiemken, and I. R. Sanders. 1998. Mycorrhizal fungal diversity determines plant biodiversity, ecosystem variability and productivity. Nature 396:69-72). Specifically, they wanted to know if it mattered which specific AMF species were present, or just that some type of AMF was present. They grew various plants in combination with one of four AMF species, no AMF, or all four AMF species together; and they measured plant growth under each set of conditions. All plant species were grown in each plot, so they always competed with each other with the only difference being which AMF species were present. Use the graphs in Figure 31.4 to answer the questions that follow. Note that the x-axis labels indicate the number and identity of AMF species (bar 0 = no fungi; bars A-D = individual AMF species; bar A+B+C+D = all AMF species together). The y-axis indicates the amount (grams)of plant biomass for the species shown in italics above each graph. Figure 31.4 -Which of the following best explains the data given in graph (b)of Figure 31.4 about Lotus corniculatus?

The fungus Saccharomyces cerevisiae is a model eukaryotic cell for genetic studies.Which of the following is an important attribute that makes this organism ideal for this purpose?

Fungi have an extremely high surface-area-to-volume ratio.What is the advantage of this to an organism that gets most of its nutrition through absorption?

The researchers then wanted to know if plant biodiversity and productivity would increase in a natural system as a result of increasing AMF diversity beyond just four species. Consider Figure 31.6 below (Figure 2 from van der Heijden et al. 1998): Figure 31.6 -Plant biomass (growth)in Figure 31.6 increases as fungal diversity increases.True or false?

This symbiotic association grows on rocks,where it begins the process of soil formation,and it is a major food source for caribou.

After looking at Figure 31.1 above,why do you think the spike in fungal abundance ended so "abruptly"? Why didn't fungal abundance remain high?

Fungi are most closely related to which of these groups?

This group of fungi has the ability to penetrate its host's cell wall,thus increasing the efficiency with which materials are passed from fungus to host.

There was a mass extinction of plants and animals at the end of the Permian period 250 million years ago.Which of the following would be a reasonable prediction for the fungal fossil record?

Most coal was formed during the Carboniferous period.What is a reasonable hypothesis that explains this observation?

The researchers then wanted to know if plant biodiversity and productivity would increase in a natural system as a result of increasing AMF diversity beyond just four species. Consider Figure 31.6 below (Figure 2 from van der Heijden et al. 1998): Figure 31.6 -The plants in graphs (b),(c),(e),and (f)have mycorrhizal associations.True or false?