Improving growth, phytochemical, and antioxidant characteristics of peppermint by phosphate-solubilizing bacteria along with reducing phosphorus fertilizer use

Abstract

Phosphorus is a vital nutrient for plant growth and development. Its deficiency in farmlands is obviated by the phosphate fertilizer application. Excessive consumption of phosphate fertilizers harms to human health and the environment. Some soil bacteria are capable to increase phosphate fertilizers efficiency. Two-year field experiment was conducted to evaluate the effect of phosphate-solubilizing bacteria inoculation with phosphorus fertilizer on growth, antioxidant status, and phytochemical features of peppermint (Mentha piperita L.). The treatments were three amounts triple superphosphate (0, 50, and 100 kg ha−1) and PSB strains (Pseudomonas putida and Pantoea agglomerans) which were arranged as factorial based on randomized complete block design. The results showed that phosphorus supplying by chemical fertilizer or PSB improved peppermint growth features included stem number, leaf length, leaf number, and dry weights of leaf, stem, and plant. The contents of photosynthetic pigments increased by chemical or biological phosphorus fertilizer application. The application of PSB with triple superphosphate reduced soluble carbohydrates and increased protein. The antioxidant enzymes activities including catalase, peroxidase, ascorbate peroxidase, and polyphenol oxidase were increased by the PSB inoculation. In contrast, activities of these enzymes were reduced by the triple superphosphate application. The highest EO yield was obtained by Pseudomonas putida and Pantoea agglomerans inoculation as phosphate-solubilizing bacteria with 50 kg ha −1 triple superphosphate. The menthol content was increased in response to the triple superphosphate and the PSB inoculation. Therefore, PSB inoculation increased phosphate fertilizer efficiency which leads to reducing phosphate fertilizer consuming and increasing the plant biomass as well as EO yield.1