Elemental composition of strawberry plants inoculated with the plant growth‐promoting bacterium A zospirillum brasilense REC 3, assessed with scanning electron microscopy and energy dispersive X ‐ray analysis

The elemental composition of strawberry plants ( F ragaria ananassa cv. M acarena) inoculated with the plant growth‐promoting bacterium A zospirillum brasilense REC 3, and non‐inoculated controls, was studied using scanning electron microscopy ( SEM ) and energy dispersive X ‐ray ( EDS ) analysis. This allowed simultaneous semi‐quantification of different elements in a small, solid sample. Plants were inoculated and grown hydroponically in 50% or 100% H oagland solution, corresponding to limited or optimum nutrient medium, respectively. Bacteria‐inoculated plants increased the growth index 45% and 80% compared to controls when grown in 100% and 50% Hoagland solution, respectively. Thus, inoculation with A . brasilense REC 3 in a nutrient‐limited medium had the strongest effect in terms of increasing both shoot and root biomass and growth index, as already described for A zospirillum inoculated into nutrient‐poor soils. SEM ‐ EDS spectra and maps showed the elemental composition and relative distribution of nutrients in strawberry tissues. Leaves contained C , O , N , N a, P , K , C a and C u, while roots also had S i and C l. The organic fraction ( C , O and N ) accounted for over 96.3% of the total chemical composition; of the mineral fraction, Na had higher accumulation in both leaves and roots. A zospirillum ‐inoculated and control plants had similar elemental quantities; however, in bacteria‐inoculated roots, P was significantly increased (34.33%), which constitutes a major benefit for plant nutrition, while C u content decreased (35.16%).