Figure 17.18 Favoring the most beneficial partner. (a) In an experiment, the wild onion plant was grown with its roots into two separate pots: one contained a beneficial mycorrhizal fungus and the other contained a nonbeneficial mycorrhizal fungus. After 9 weeks of growth, researchers were able to determine whether the plant allocates more of its photosynthetic products to the beneficial or nonbeneficial fungus. (b) Because the plant can distinguish between the two fungal species, it is able to allocate more of its photosynthetic products to the more beneficial fungus. Error bars are standard errors.

Data from J. D. Bever et al., Preferential allocation to beneficial symbiont with spatial structure maintains mycorrhizal mutualism, Ecology Letters 12 (2009): 13–21.