Silicon enrichment alters functional traits in legumes depending on plant genotype and symbiosis with nitrogen-fixing bacteria

1. Silicon (Si) uptake and deposition (silicification) in tissues is known to alleviate stresses and generally improve plant health. This is mostly studied in Si-high accumulators, such as grasses, with comparatively less known about its effects on other plant functional groups, such as legumes. There is speculation that Si may positively impact the symbiosis between legumes and the nitrogen-fixing bacteria (rhizobia) they associate with, but this is poorly understood. This study examined the effects of Si enrichment on legume species associated with rhizobia and the potential underlying mechanism of Si impacts.

2. We conducted a glasshouse experiment with lucerne (Medicago sativa) and barrel medic (M. truncatula) associated with a model rhizobial strain. Six genotypes (three per species) were either supplemented with Si (+Si) or untreated (-Si). We quantified 16 functional traits which could be classified as plant growth, physiology, elemental chemistry, nodule activity and nitrogen...