Nitrogen metabolism, plant growth, leaf gas exchange and stomata density under inoculation of Pseudomonas fluorescens and Azospirillum brasilense into hydroponic arugula
Abstract
Plant growth-promoting bacteria may improve nutrient acquisition and physiological performance in hydroponic crops, but the benefits of increasing inoculant concentration remain poorly understood. Two independent experiments were conducted to evaluate Pseudomonas fluorescens strain CCTB03 and Azospirillum brasilense strains AbV5 and AbV6 in hydroponically grown arugula. In each experiment, inoculants were applied once to the recirculating nutrient solution to obtain nominal initial concentrations of 0, 3.2 × 104, or 6.4 × 104 CFU mL−1. In the A. brasilense experiment, the nominal initial concentration of 3.2 × 104 CFU mL−1 increased shoot N accumulation by 144% relative to the corresponding non-inoculated control. In the independent P. fluorescens experiment, the same nominal initial concentration increased shoot N accumulation by 202% relative to its respective non-inoculated control. Nitrate reductase activity increased by 1035% with A. brasilense, while P. fluorescens increased this activity by 2194 and 2063% at 3.2 × 104 and 6.4 × 104 CFU mL−1, respectively. Inoculation also reduced shoot NO3− accumulation by at least 35% with A. brasilense and 44% with P. fluorescens, while increasing NH4+ and mineral nutrient accumulation. Both inoculants increased CO2 assimilation, stomatal conductance, transpiration, intercellular CO2 concentration, stomatal density, and plant biomass, whereas water-use efficiency remained unchanged. Across several nutritional and growth variables, 3.2 × 104 CFU mL−1 produced responses equal to or greater than those obtained with 6.4 × 104 CFU mL−1. Thus, doubling the nominal bacterial concentration did not consistently provide additional benefits under the conditions of this study.
Related
- Azospirillum brasilense and cytidine as combination treatment to enhance drought resilience of peas
- Growth promotion of maize and metabolomic profiling of Azospirillum brasilense cultures at varying incubation times.
- Diffusible signals from Azospirillum brasilense promote rice growth and induce distinct gene expression changes in plant roots
- Enhancement of Drought Stress Tolerance in Lettuce by Pseudomonas fluorescens FSO7 Isolated from Artemisia ordosica Rhizosphere
- A GacS-mediated regulatory framework coordinates bacterial competition and rhizosphere microbiome remodeling in Pseudomonas fluorescens
BibTeX
@article{giolo2026nitrogen,
title = {{Nitrogen metabolism, plant growth, leaf gas exchange and stomata density under inoculation of Pseudomonas fluorescens and Azospirillum brasilense into hydroponic arugula}},
author = {Victória Moraes Giolo and Carlos Eduardo da Silva Oliveira and Vitória Almeida Moreira Girardi and Andrea de Castro Bastos and Sthela Silva Melo and Mariana Cristina Barbosa and Evelin Camargo Garcia and Italo Ferreira Vetruve and Eduardo Pradi Vendruscolo and Enes Furlani Junior and Aline Redondo Martins and Marcelo Carvalho Minhoto Teixeira Filho},
journal = {Frontiers in Plant Science},
year = {2026},
month = nov,
doi = {10.3389/fpls.2026.1959277},
url = {https://www.frontiersin.org/articles/10.3389/fpls.2026.1959277},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Nitrogen metabolism, plant growth, leaf gas exchange and stomata density under inoculation of Pseudomonas fluorescens and Azospirillum brasilense into hydroponic arugula
AU - Victória Moraes Giolo
AU - Carlos Eduardo da Silva Oliveira
AU - Vitória Almeida Moreira Girardi
AU - Andrea de Castro Bastos
AU - Sthela Silva Melo
AU - Mariana Cristina Barbosa
AU - Evelin Camargo Garcia
AU - Italo Ferreira Vetruve
AU - Eduardo Pradi Vendruscolo
AU - Enes Furlani Junior
AU - Aline Redondo Martins
AU - Marcelo Carvalho Minhoto Teixeira Filho
PY - 2026
DA - 2026/11/09
JO - Frontiers in Plant Science
DO - 10.3389/fpls.2026.1959277
UR - https://www.frontiersin.org/articles/10.3389/fpls.2026.1959277
AB - Plant growth-promoting bacteria may improve nutrient acquisition and physiological performance in hydroponic crops, but the benefits of increasing inoculant concentration remain poorly understood. Two independent experiments were conducted to evaluate Pseudomonas fluorescens strain CCTB03 and Azospirillum brasilense strains AbV5 and AbV6 in hydroponically grown arugula. In each experiment, inoculants were applied once to the recirculating nutrient solution to obtain nominal initial concentrations of 0, 3.2 × 104, or 6.4 × 104 CFU mL−1. In the A. brasilense experiment, the nominal initial concentration of 3.2 × 104 CFU mL−1 increased shoot N accumulation by 144% relative to the corresponding non-inoculated control. In the independent P. fluorescens experiment, the same nominal initial concentration increased shoot N accumulation by 202% relative to its respective non-inoculated control. Nitrate reductase activity increased by 1035% with A. brasilense, while P. fluorescens increased this activity by 2194 and 2063% at 3.2 × 104 and 6.4 × 104 CFU mL−1, respectively. Inoculation also reduced shoot NO3− accumulation by at least 35% with A. brasilense and 44% with P. fluorescens, while increasing NH4+ and mineral nutrient accumulation. Both inoculants increased CO2 assimilation, stomatal conductance, transpiration, intercellular CO2 concentration, stomatal density, and plant biomass, whereas water-use efficiency remained unchanged. Across several nutritional and growth variables, 3.2 × 104 CFU mL−1 produced responses equal to or greater than those obtained with 6.4 × 104 CFU mL−1. Thus, doubling the nominal bacterial concentration did not consistently provide additional benefits under the conditions of this study.
SN - 1664-462X
ER -