Interactions between mycorrhizal fungi and sex-specific physiology in Distichlis spicata.

Background/Question/Methods:

Sex-specific differences in physiology have been found to occur in many angiosperms, and have been proposed to explain biased population sex ratios. Here, we tested this idea in the dioecious, saltmarsh grass Distichlis spicata, which has extremely skewed sex ratios, and exhibits spatial segregation of the sexes. In the greenhouse, we grew D. spicata in treatments in which phosphate level (low and high) and mycorrhizal fungi infection (with and without) were varied.  Using the LI-COR 6400, we measured photosynthesis, conductance, and respiration.

Results/Conclusions:

We found sex-specific differences in physiology in D. spicata that differed with mycorrhizal fungi infection. Photosynthetic rate, conductance, and respiration rate varied between males and females. The presence of mycorrhizal infection lessened the degree of difference between the sexes and also significantly increased the rate of respiration. These results suggest that there are significant physiological differences between males and females in this species and that they are affected by mycorrhizal symbiosis. These interacting factors may help explain the biased population sex ratios.