Abstract: Recent studies have shown that plant responses to neighboring plants are correlated with the “identity” of neighbors. Dioecious plants play crucial role in maintaining ecosystem functions. Few studies have focused on how dioecious plants respond to neighbors with different genders. In this study, we compared the direction and intensity of neighbor effects on biomass and root morphology of female/male seedlings grown with sex-associated neighbors in the important economic and ecological tree species, Morus alba. The results showed that: (1) stem biomass and total biomass of both male and female mulberry trees were significantly reduced under intra-sex neighbors, compared with the condition without neighbors. Under intersex neighbors, root biomass of females was significantly increased, and stem biomass and total biomass of males were significantly reduced. (2) In terms of neighbor effects, intra-sex neighbors had significant negative effects on root biomass, leaf biomass, leaf weight ratio, total root volume and total root surface area of female plants, and showed significant positive effects on male plants. Inter-sex neighbors had significant negative effects on stem biomass, total biomass, and stem weight ratio of both male and female mulberry trees, and had significant positive effects on root weight ratio, root shoot ratio and total root volume. (3) Total root surface area and total root volume of female plants were significantly smaller than those of male plants under intra-sex neighboring plants, while those of female plants were significantly larger than those of male plants under inter-sex co-planting. These results demonstrated that the response of mulberry to neighboring plants was related to the sex of neighboring plants, and this response was sex-specific. By exploring plant neighbor effect from the perspective of plant sex, our results may provide new research content investigating plant-plant interactions and offer novel insights for the establishment of high-yielding mulberry plantations.

Key words: mulberry, neighbor effect, growth, dioecious plant