Microbiological Biostimulants in the Improvement of Extended Storage Quality of In Vitro-Derived Plants of Popular Ornamental Perennials

In vitro propagation is a crucial method for the mass production of high-quality plants, but the impact of microbiological interventions during ex vitro storage remains an underexplored aspect. This study aims to assess the effects of three commercial biostimulants in the form of microbiological preparations-BactoFungiStop, AzotoPower, and Guard-applied over six months through foliar sprays on the post-storage quality of Brunnera macrophylla 'Silver Heart', Echinacea purpurea 'Secret Glow', Heuchera x hybrida 'Northern Exposure Red', Persicaria amplecicaulis 'JS Caliente', and Rudbeckia x hybrida 'Sunbeckia Sophia Yellow' plants. The monthly application of microbiological preparations adhered to the concentrations recommended by producers. Post-storage evaluations included shoot and root parameters, leaf morphology, and chlorophyll biosynthesis. All microbiological preparations positively influenced shoot elongation in B. macrophylla 'Silver Heart'. The microbiological treatments stimulated root development in this species, i.e., increased root length, area, volume, and the number of root forks and tips. In E. purpurea 'Secret Glow', all three preparations enhanced shoot length, leaf parameters, and root traits, with Guard demonstrating the highest efficacy. As for P. amplecicaulis 'JS Caliente', BactoFungiStop negatively affected shoot and leaf parameters but promoted root development. Heuchera x hybrida 'Northern Exposure Red' exhibited increased shoot and leaf dimensions with all microbiological treatments, while Rudbeckia x hybrida 'Sunbeckia Sophia Yellow' displayed positive responses in shoot-related traits but no impact on root development. None of the microbiological preparations influenced chlorophyll biosynthesis in any of the studied species. The results of our research can be implemented in the large-scale production of ornamental plants.