Bioinoculation with Bacillus spp. and its physiological effects on the performance of maize seedlings

Abstract

Abstract The growing demand for sustainable alternatives in agriculture has stimulated the use of plant growth-promoting microorganisms as a strategy to improve the early performance of crops. In this context, the objective of this study was to evaluate the initial physiological effects of a commercial bioinoculant containing Bacillus spp. on maize (Zea mays L.) seedlings grown in sterile sand under controlled conditions. The experiment was conducted using five bioinoculant doses (0, 50, 100, 150, and 200 µL), arranged in a completely randomized design with four replicates. Morphological variables (seedling emergence, root and shoot length, and dry mass), physiological parameters (chlorophyll a fluorescence and gas exchange), as well as anatomical and histochemical characteristics, were evaluated. The data were analyzed by analysis of variance, principal component analysis (PCA), and Spearman's rank correlation (ρ). The 100 µL treatment was associated with the highest seedling emergence (85%), greater root development, increased root biomass accumulation, and higher potential quantum efficiency of photosystem II (Fv/Fm). In contrast, the highest bioinoculant dose (200 µL) was associated with anatomical alterations and increased non-regulated energy dissipation, suggesting greater physiological stress under the experimental conditions. Principal component analysis indicated that the 100 µL treatment was associated with variables related to early seedling growth and photochemical efficiency, whereas Spearman's correlation revealed positive associations between root growth and photosynthetic performance. Overall, the results suggest that the 100 µL dose promoted the most favorable morphophysiological responses during the initial development of maize seedlings. These findings indicate that the appropriate use of Bacillus spp., based bioinoculants represents a promising strategy for improving early crop establishment and may contribute to more efficient and sustainable production systems.