Talking with Strangers: Improving Serianthes Transplant Quality with Interspecific Companions

Mixtures of species in natural or agricultural systems can increase the performance of individuals or groups relative to monocultures, often through facilitative mechanisms. Mechanisms include root communication by which plants can interrogate the identity of adjacent plants and respond negatively or positively. Alternatively, mixtures of species can ameliorate the harmful effects of soil biota that are pronounced in monocultures, thereby improving plant productivity. Limited investments into roots by shade-grown Serianthes plants in nurseries have been correlated with reduced survival after transplantation to forested habitats. We used companion container cultures in two studies to determine if heterospecific neighbor, or stranger roots could experimentally increase the root growth of Serianthes grandiflora plants used as surrogates for the critically endangered Serianthes nelsonii. In one study, native sympatric eudicot and pteridophyte companions increased relative root growth and conspecific companions decreased root growth in comparison to control plants that were grown with no companions. In a second study, the phylogeny of companion plants elicited different root growth responses following the order of congeneric < eudicot = monocot < gymnosperm < pteridophyte. We propose the use of stranger roots that are experimentally maintained in production containers as a passive protocol to improve relative and absolute root growth, leading to improved post-transplant growth and survival of container-grown Serianthes plants.

Automated summary

Mixtures of species in natural or agricultural systems can enhance the performance of individuals through facilitative mechanisms, such as root communication, or by ameliorating harmful effects of soil biota. In this study, using companion container cultures, it was found that heterospecific neighbors could experimentally increase root growth of the critically endangered Serianthes plants, while conspecific companions decreased root growth. These findings suggest the use of stranger roots as a passive method to improve post-transplant growth and survival of container-grown Serianthes plants.