Kin recognition and inter-sexual competition in a dioecious grass

Background/Question/Methods

Plants have evolved complex mechanisms to recognize and respond to the presence of neighboring plants. Recent studies on root identity have found that roots are able to differentiate among neighboring roots based on whether the neighbor is self/non-self or kin/stranger. We used the species Distichlis spicata, a perennial, dioecious, monocot which exhibits spatial segregation of the sexes in which microhabitats are either nearly 100% male or 100% female to examine the ability of seedlings to respond to genotypes of different relatedness and different sexes. We conducted a series of experiments in which we exposed the roots of seedlings to liquid media previously occupied by other D. spicata plants, which varied in sex, the genotype of the mother, and the populations from which they were derived. 

Results/Conclusions

We found that D. spicata plants respond to the sex and genetic relatedness of competitors (detecting either additional exudates to the media and/or removal of nutrients), and that this response occurs in the number of lateral roots and root length. Combined with field and greenhouse data, these results help explain extreme sex ratio variation found in this species.