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Unformatted text preview: association. e) Describe two differences between determinant and indeterminate nodules. 2) The article describes three life strategies seen in rhizobia. When multiple strains of rhizobium infect a single plant, this sets up a scenario for cheaters (also known as parasitic rhizobia) to enter the plant. a) Describe how a cheater differs from a non-cheating strain. b) How does cheating benefit the parasitic rhizobium? c) The authors describe a cleaver laboratory experiment where they manipulated the N 2 available to individual nodules of a single plant. Some nodules were exposed to atmospheric levels of N 2 while some had no available N 2 . How did the plant sanction the nodules that were unable to fix nitrogen? d) Describe a way in which a cheater could avoid plant sanctions. 3) What circumstances would allow free-living (non-symbiotic) rhizobia to out compete (and proliferate more than) a symbiotic form?...
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