Yield, nutrition, and leaf gas exchange of lettuce plants in a hydroponic system in response to Bacillus subtilis inoculation

Carlos Eduardo da Silva Oliveira; Arshad Jalal; Jailson Vieira Aguilar; Liliane Santos de Camargos; Tiago Zoz; Bhim Bahadur Ghaley; Mostafa A Abdel-Maksoud; Khaloud Mohammed Alarjani; Hamada AbdElgawad; Marcelo Carvalho Minhoto Teixeira Filho

doi:10.3389/fpls.2023.1248044

Yield, nutrition, and leaf gas exchange of lettuce plants in a hydroponic system in response to Bacillus subtilis inoculation

Front Plant Sci. 2023 Oct 25:14:1248044. doi: 10.3389/fpls.2023.1248044. eCollection 2023.

Affiliations

¹ Department of Plant Protection, Rural Engineering and Soils, School of Engineering, São Paulo State University - UNESP-FEIS, Ilha Solteira, São Paulo, Brazil.
² Department of Biology and Zootechnics, Lab of Plant Morphology and Anatomy/Lab Plant Metabolism and Physiology, School of Engineering, São Paulo State University - UNESP-FEIS, Ilha Solteira, São Paulo, Brazil.
³ Department of Crop Science, State University of Mato Grosso do Sul - UEMS, Mundo Novo, Mato Grosso do Sul, Brazil.
⁴ Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Copenhagen, Denmark.
⁵ Botany and Microbiology Department, College of Science, King Saud University, Riyadh, Saudi Arabia.
⁶ Laboratory for Molecular Plant Physiology and Biotechnology, Department of Biology, University of Antwerp, Antwerp, Belgium.

Abstract

Inoculation with Bacillus subtilis is a promising approach to increase plant yield and nutrient acquisition. In this context, this study aimed to estimate the B. subtilis concentration that increases yield, gas exchange, and nutrition of lettuce plants in a hydroponic system. The research was carried out in a greenhouse in Ilha Solteira, Brazil. A randomized block design with five replications was adopted. The treatments consisted of B. subtilis concentrations in nutrient solution [0 mL "non-inoculated", 7.8 × 10³, 15.6 × 10³, 31.2 × 10³, and 62.4 × 10³ colony forming units (CFU) mL^-1 of nutrient solution]. There was an increase of 20% and 19% in number of leaves and 22% and 25% in shoot fresh mass with B. subtilis concentrations of 15.6 × 10³ and 31.2 × 10³ CFU mL^-1 as compared to the non-inoculated plants, respectively. Also, B. subtilis concentration at 31.2 × 10³ CFU mL^-1 increased net photosynthesis rate by 95%, intercellular CO₂ concentration by 30%, and water use efficiency by 67% as compared to the non-inoculated treatments. The concentration of 7.8 × 10³ CFU mL^-1 improved shoot accumulation of Ca, Mg, and S by 109%, 74%, and 69%, when compared with non-inoculated plants, respectively. Inoculation with B. subtilis at 15.6 × 10³ CFU mL^-1 provided the highest fresh leaves yield while inoculation at 15.6 × 10³ and 31.2 × 10³ CFU mL^-1 increased shoot fresh mass and number of leaves. Concentrations of 7.8 × 10³ and 15.6 × 10³ increased shoot K accumulation. The concentrations of 7.8 × 10³, 15.6 × 10³, and 31.2 × 10³ CFU mL^-1 increased shoot N accumulation in hydroponic lettuce plants.

Keywords: Lactuca sativa L.; biological nitrogen fixation; growth-promoting bacteria; photosynthetic efficiency; water use efficiency.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This research was funded by the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP, grant number: 2020/11621-0). The Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) granted the doctoral fellowship for the first author (CNPq/TWAS grant number: 166331/2018-0) and the research productivity fellowship (award number: 311308/2020-1) for the corresponding author. This study was supported by the ECOTWINS [Research Capacity Building and Upskilling and Upgrading the Research Team in NUBiP (Ukraine) on Agroecological Intensification for Crop Production] project. ECOTWINS has received funding from the Horizon Europe Framework Programme (HORIZON) under grant agreement number 101079308 and Researchers Supporting Project number (RSPD2023R725) King Saud University, Riyadh, Saud Arabia.