Female poplar plants balance stress tolerance with competitive and ruderal strategies to grow better in opposite-sex than same-sex donor-conditioned solution

Below-ground interactions have been considered critical, but it is still unclear how dioecious plants respond in terms of growth and plant ecological strategy to root-derived compounds of the same and opposite sexes. Female and male Populus cathayana seedlings were used and exposed to donor-conditioned solution of the same sex (S exu ) and opposite sex (O exu ) for 40 days, and the growth, ecological strategies (i.e., competitiveness (C), stress tolerance (S), ruderality (R)), and related traits of leaves and roots were compared. Our results showed that compared with the treatment with S exu , the treatment with O exu significantly increased concentrations of leaf nutrient (i.e., nitrogen (N), potassium (K)), as well as fresh weight increase and relative fresh weight increase of female plants. Additionally, when exposed to the O exu , females exhibited a strategic shift toward greater C and R scores, accompanied by reduced S score. This trade-off was consistent with the observed increases in traits related to resource occupancy and exploration (e.g., root length, root volume), efficiency of resource acquisition (e.g., specific root length), as well as the decreases in traits related to stress tolerance (e.g., carbon-to-nitrogen (C/N) ratio). By contrast, males showed no significant changes in growth or CSR-derived strategy, but leaf N concentration was significantly lower when exposed to the Oexu; leaf P and K concentrations showed only non-significant numerical decreases. These findings suggest that donor-conditioned solutions can elicit sex-specific responses in both growth and CSR-derived strategies of P. cathayana , providing a basis for future investigations into the mechanisms underlying sex-specific belowground interactions.