DOI: 10.5061/dryad.fttdz08tj
title: Silicon enrichment alters functional traits in legumes depending on plant genotype and symbiosis with nitrogen-fixing bacteria

description: 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 fixation. 3.
 The two legume species responded to Si distinctively. For example, Si
 supplementation increased shoot biomass by more than 10% in lucerne but
 growth was unaffected in barrel medic. Conversely, nitrogen-fixing enzyme
 (nitrogenase) activity was promoted by more than 85% in +Si barrel medic
 plants but not in lucerne. Moreover, Si supplementation of lucerne
 increased the concentrations of Si in leaves by more than 36% but not in
 root nodules. Increased foliar concentrations of Si in lucerne was
 positively associated with increased shoot and root biomass in Sequel and
 Trifecta genotypes, respectively. Conversely, Si supplementation of barrel
 medic increased the concentration of Si in root nodules by 29% but not
 that in foliar tissues. Nitrogenase activity and where silicification
 occurred, differed between genotypes in barrel medic; nitrogenase activity
 was correlated with concentrations of Si in root nodules rather than that
 in foliar tissues in one genotype (Sephi) but the reverse was true in
 another (Hannaford). 4.This study demonstrates that two closely related
 legume species can respond to Si in distinct ways, depending on plant
 genotype and symbiosis. These results present the overlooked function of
 Si in legume-rhizobia interactions, which could potentially enhance
 productivity of this important group of plants.
description: Data are uploaded in the format of excel file that consists of
 two datasets separated into two tabs. The first tab 'L_M.
 sativa' refers to the first dataset belongs to Lucerne
 (<em>Medicago sativa</em>) and the second tab 'B_M.
 truncatula' refers to the second dataset belongs to Barrel medic
 (<em>Medicago truncatula</em>). Each of datasets consist of
 the same label, explained below. Lastly, any 'na' written down
 in column data indicates the missing values. Collumn Letter Label Description 
 A ID
 Unique identifier of each individual plant or biological
 replicate B
 Genotype Unique identifier of each genotype
 belongs to lucerne: L_HR/SQ/TR or barrel medic: B_HN/JM/SP
 C Si
 supply Silicon treatment: -Si (0 mM) or +Si (2
 mM) D
 Shoot biomass Dry shoot mass of the
 plant E
 Root biomass Dry root mass of the
 plant F
 Total biomass Total dry mass of the
 plant G
 Nodule biomass Dry mass of the nodules per
 plant H
 Nodule Si Nodule concentrations of
 silicon I
 Nitrogenase Nodule concentrations of
 nitrogenase activity 
 J Foliar Si Foliar
 concentrations of silicon 
 K Foliar C Foliar
 concentrations of carbon 
 L Foliar N Foliar
 concentrations of nitrogen 
 M Foliar C/N Foliar
 concentrations of carbon:nitrogen ratio 
 N Total chlorophyll
 Foliar concentrations of chlorophyll in SPAD unit
 O Photosynthetic
 rate Measure of the rate of photosynthesis in the
 foliage P
 Stomatal conductance Measure of the degree
 of stomatal opening 
 Q δ<sup>15</sup>N
 A measure of the ratio of the two stable isotopes of nitrogen
 (<sup>15</sup>N:<sup>14</sup>N)
 R Ndfa
 The amount of nitrogen fixed by rhizobia 
 S N fractionation
 The ratio between nitrogen fixed by rhizobia and nitrogen uptake
 from the soil