Root positioning and trait shifts in Hibbertia racemosa as dependent on its neighbour's nutrient‐acquisition strategy

• Published in: Plant, cell and environment cell and environment, 2021-04, Vol.44 (4), p.1257-1267
• Main Authors: Britto Costa, Patrícia, Staudinger, Christiana, Veneklaas, Erik J., Oliveira, Rafael S., Lambers, Hans
• Format: Article
• Language: English
• Subjects: Attenuation; Biomass; biotic interactions; carboxylates; cluster roots; Clusters; Computer architecture; Conspecifics; facilitation; neighbourhood effects; Nutrient availability; Nutrient concentrations; Plant diversity; Plant growth; plant–plant interactions; root aggregation; root spatial patterns; root system architecture; Roots; specific root length; Sympatric populations
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.13991

Nutrient‐poor ecosystems globally exhibit high plant diversity. One mechanism enabling the co‐existence of species in such ecosystems is facilitation among plants with contrasting nutrient‐acquisition strategies. The ecophysiological processes underlying these interactions remain poorly understood. We hypothesized that root positioning plays a role between sympatric species in nutrient‐poor vegetation. We investigated how the growth traits of the focal mycorrhizal non‐cluster‐rooted Hibbertia racemosa change when grown in proximity of non‐mycorrhizal Banksia attenuata, which produces cluster roots that increase nutrient availability, compared with growth with conspecifics. Focal plants were placed in the centre of rhizoboxes, and biomass allocation, root system architecture, specific root length (SRL), and leaf nutrient concentration were assessed. When grown with B. attenuata, focal plants decreased root investment, increased root growth towards B. attenuata, and positioned their roots near B. attenuata cluster roots. SRL was greater, and the degree of localized root investment correlated positively with B. attenuata cluster‐root biomass. Total nutrient contents in the focal individuals were greater when grown with B. attenuata. Focal plants directed their root growth towards the putatively facilitating neighbour's cluster roots, modifying root traits and investment. Preferential root positioning and root morphological traits play important roles in positive plant–plant interactions. With an experimental design using rhizoboxes, we aimed to assess root–root interactions in putatively facilitative inter‐specific interactions. We highlight that sympatric plant species with contrasting nutrient‐acquisition strategies allow positive plant–plant interactions via preferential root positioning.