Talking with Strangers: Improving Serianthes Transplant Quality with Interspecific Companions

Thomas E Marler,Ragan M Callaway

doi:10.3390/f12091192

Abstract

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.

Highlights

Anthropogenic use of polycultures to increase productivity above that of monocultures is rooted in ancient agricultural systems [1,2]
Serianthes grandiflora seeds sourced from Bohol Island, Philippines were used to produce all target plants and conspecific companion plants
Serianthes kanehirae seeds sourced from Yap Island, Federated States of Micronesia were used for congeneric companion plants

Summary

Introduction

Anthropogenic use of polycultures to increase productivity above that of monocultures is rooted in ancient agricultural systems [1,2]. Li et al [5] found that root exudates from Zea mays L. promoted Vicia faba L. nodulation and increased N2 -fixation to increase Z. mays productivity when the two species were intercropped. Such biodiversity effects in modern cropping systems are supported by ancient origins and contemporary ecological research [6]. Other experimental and observational studies have advanced our understanding of how such root behavior contributes to the over-yielding that often accompanies biodiversity [4,7,8,9,10,11] Some of these studies indicate mechanisms other than nutrient enrichment. Mommer et al [12] found that total root production increased more than 40% in polycultures, relative to monocultures, and attributed this to complex recognition processes, and partly to diversity-driven decreases in pathogens [13]

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Conclusion