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

Citation

Putra, Rocky et al. (2021), Silicon enrichment alters functional traits in legumes depending on plant genotype and symbiosis with nitrogen-fixing bacteria, Dryad, Dataset, https://doi.org/10.5061/dryad.fttdz08tj

Abstract

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.

Usage Notes

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 (Medicago sativa) and the second tab 'B_M. truncatula' refers to the second dataset belongs to Barrel medic (Medicago truncatula). 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 δ15N A measure of the ratio of the two stable isotopes of nitrogen (15N:14N)
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