Multi-Channel Neighbor Interactions Adjust Growth Strategies in the Clonal Plant Glechoma grandis.

Background

Plant-plant interactions rely on neighbor-derived cues. Access to multiple cue channels should allow better identity assessment, yet integrative studies-especially on touch between neighbors-remain limited.

Methods

We tested how leaf contact and shared rooting space between neighbors influence plant-plant interactions, by measuring growth of Glechoma grandis paired with conspecific, congeneric, or distant heterospecific neighbors.

Results

Neighbor effect strength depended on interaction mode: leaf contact alone triggered stronger neighbor identity-dependent growth than shared rooting space alone, and combined channels were strongest. With both channels, plants were a conservative strategy toward conspecifics (reducing stolon allocation), but competitive toward heterospecifics (increasing leaf area and roots, stolons and leaf biomass). The competitive strategy further diverged with phylogenetic distance-congeneric neighbors induced thicker stolons; distant heterospecific neighbors led to longer, thinner stolons. Moreover, interaction mode outweighed neighbor identity: without interactions, neighbor effects differed only between conspecific and heterospecific neighbors (conspecifics induced longer stolons and more ramets, indicating greater expansion, but heterospecific neighbors did not differ); with interactions, leaf contact mainly affected leaf area, shared rooting space affected root allocation, and combined channels eliminated differences in G. grandis among neighbors combinations.

Conclusions

Leaf contact triggered the most obvious neighbor identity-dependent growth responses, whereas the combination of leaf contact and shared rooting space caused convergence of growth responses among neighbor combinations.