AUTHOR=Oliveira Carlos Eduardo da Silva , Sena Oliveira Thaissa Julyanne Soares , Jalal Arshad , Fernandes Guilherme Carlos , Bastos Andréa de Castro , da Silva Marcelo Rinaldi , Sant’Ana Gabriela Rodrigues , Aguilar Jailson Vieira , de Camargos Liliane Santos , Zoz Tiago , Teixeira Filho Marcelo Carvalho Minhoto TITLE=Inoculation and co-inoculation of lettuce and arugula hydroponically influence nitrogen metabolism, plant growth, nutrient acquisition and photosynthesis JOURNAL=Frontiers in Plant Science VOLUME=Volume 16 - 2025 YEAR=2025 URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2025.1547821 DOI=10.3389/fpls.2025.1547821 ISSN=1664-462X ABSTRACT=The objective of this study was to investigate the effects of single and combined inoculations of A. brasilense, B. subtilis and P. fluorescens on lettuce and arugula grown in a hydroponic system. The study was carried out in a greenhouse and was designed in randomized blocks with five replications. The treatments consisted of inoculation with A. brasilense, B. subtilis and P. fluorescens and co-inoculation with A. brasilense + B. subtilis, A. brasilense + P. fluorescens, B. subtilis + P. fluorescens and A. brasilense + B. subtilis + P. fluorescens via nutrient solution. An increase in the length and fresh mass of the shoot and leaf chlorophyll concentrations of arugula and lettuce was observed under co-inoculations of A. brasilense + P. fluorescens and B. subtilis + P. fluorescens. Greater length, fresh mass and volume of the lettuce root system were observed under the co-inoculations of A. brasilense + B. subtilis, A. brasilense + P. fluorescens and B. subtilis + P. fluorescens in arugula under the inoculations of A. brasilense and A. brasilense + P. fluorescens. Greater nitrate reductase activity was detected in leaves, and lower nitrate accumulation was detected in lettuce and arugula under inoculations with A. brasilense, P. fluorescens and B. subtilis + P. fluorescens. The greatest accumulation of N, P, K, Ca and Mg in the lettuce shoot was obtained under inoculation with P. fluorescens, A. brasilense + P. fluorescens and B. subtilis + P. fluorescens. Co-inoculation with A. brasilense + P. fluorescens and B. subtilis + P. fluorescens was the most efficient combination for increasing the growth, nutrient acquisition and functioning of nitrogen metabolism in arugula lettuce plants.