Exam 31: Fungi

Canadian and Swiss researchers (van der Heijden et al., 1998)interested in factors affecting biodiversity, grew a variety of grassland plants in combination with one of four arbuscular mycorrhizal (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 were present. Use the graphs in Figure 31.5 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. Graph (e)is the total biomass (grams)of all 11 plant species combined; graph (f)is the biomass of Bromus erectus plants only, separated from the total. Figure 31.4 Figure 31.5 -Why does total biomass (graph e,Figure 31.5)not vary with AMF diversity?

Microsporidians are considered parasitic because of the ability to penetrate their host cells using this structure.

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 graphs shown above,which of the following plant species is most likely not to form mycorrhizal associations?

Figure 31.3 -Referring to Figure 31.3 (Simard et al.,1997-third-year seedlings only),shown above,was there a net transfer of carbon from plants in sunlight to plants in shade?

Canadian and Swiss researchers (van der Heijden et al., 1998)interested in factors affecting biodiversity, grew a variety of grassland plants in combination with one of four arbuscular mycorrhizal (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 were present. Use the graphs in Figure 31.5 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. Graph (e)is the total biomass (grams)of all 11 plant species combined; graph (f)is the biomass of Bromus erectus plants only, separated from the total. Figure 31.4 Figure 31.5 -Using grams of biomass as an indicator of abundance,which species is most likely the dominant species in this ecosystem (see Figure 31.5)?

Which fungal class is not matched with its most common habitat?

Based on the idea that fungi have pores between their cell walls,allowing cytoplasm to move from one end of the mycelium to the other,which of the following hypotheses is the most plausible?

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 -If the number of mycorrhizal fungal species increases to 20,the amount of P in the soil will likely decline to zero (Figure 31.6).True or false?

It has been hypothesized that fungi and plants have a mutualistic relationship because plants make sugars available for the fungi's use.What is the best evidence in support of this hypothesis?

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. Describe what you believe would be the best method of providing the appropriate fungi to the newly transplanted pines described in the previous question.Be sure to identify the source of the fungi and the stage of the life cycle during which you would transport them.Also explain how you would introduce the fungi to their new home.Explain why you believe your method would work,including relevant elements of fungal biology.

Canadian and Swiss researchers (van der Heijden et al., 1998)interested in factors affecting biodiversity, grew a variety of grassland plants in combination with one of four arbuscular mycorrhizal (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 were present. Use the graphs in Figure 31.5 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. Graph (e)is the total biomass (grams)of all 11 plant species combined; graph (f)is the biomass of Bromus erectus plants only, separated from the total. Figure 31.4 Figure 31.5 -What is the major difference between Bromus erectus (graph f)and the other plant species (graphs a-d)included in the study?

It has been hypothesized that fungi and plants have a mutualistic relationship because fungi provide critical nitrogen for the plants' use.How do we know this happens?

Why is it reasonable to hypothesize that lichens might predict air quality?

Which of these fungal features supports the phylogenetic conclusion that fungi are more closely related to animals than plants?

Why are mycorrhizal fungi superior to plants at acquiring mineral nutrition from the soil?

Basidiomycetes are the only fungal group capable of synthesizing lignin peroxidase.What advantage does this group of fungi have over other fungi because of this capability?

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 -Referring to Simard et al.(1997),which design element is the control in this experiment and why?

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 -Referring to Simard et al.(1997),what is the result that would most strongly refute their hypothesis?

Canadian and Swiss researchers (van der Heijden et al., 1998)interested in factors affecting biodiversity, grew a variety of grassland plants in combination with one of four arbuscular mycorrhizal (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 were present. Use the graphs in Figure 31.5 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. Graph (e)is the total biomass (grams)of all 11 plant species combined; graph (f)is the biomass of Bromus erectus plants only, separated from the total. Figure 31.4 Figure 31.5 -Based on graphs (e)and (f)in Figure 31.5,which is the most well-supported prediction for the effect on total plant biomass if AMF diversity were increased to eight species?

Why is it important that ectomycorrhizal fungi (EMF)have peptidase enzymes?