It is known that applications of boron, which is known to play an essential role in nutrient transport by plant membranes, can affect the accumulation and use of other plant nutrients as a regulator or an inhibitor. Thus, in this study, the effects of boron doses (0=control, 5, 10, 20 mM) and some beneficial rhizobacteria (Azospirillum lipoferum, Bacillus megaterium, and Frateuria aurentia) on seedling growth, physiological, and biochemical parameters of purple basil (Ocimum basilicum) were investigated. The study was carried out in as a factorial experiment in a completely randomized design with four replications in a controlled climate chamber. In the study, plant root, seedling length, root and seedling fresh-dry weight, total chlorophyll, carotenoid, anthocyanin, flavonol, nitrogen balance index, MDA, relative water in leaf tissues, ion leakage, and membrane stability parameters were investigated. It was observed that all growth parameters were negatively affected by increasing boron doses. In contrast, while ion leakage, total flavonol, carotenoid, anthocyanin, and MDA contents increased, membrane stability, total chlorophyll content, and nitrogen balance index contents decreased. Rhizobacteria applications were found to be effective in reducing toxic boron damage in root length and seedling fresh weight, increasing total chlorophyll, and anthocyanin contents, and decreasing boron toxicity by reducing lipid peroxidation compared to control.

27.3.2022