Histological and Physiological Study of the Effects of Biostimulants and Plant Growth Stimulants in Viburnum opulus ‘Roseum’

Biostimulants and other plant growth promoters can provide an effective solution to the challenge of urbanisation and climate change. Viburnum opulus ‘Roseum’ is a globally popular deciduous shrub species that can be made more resistant to urban influences by using natural growth-promoting substances. In our study, we investigated the effects of growth promoters Kelpak®, Bistep and Yeald Plus on the species, both histologically and physiologically (proline stress hormone measurement). Our measurements were complemented using the analysis of rhizosphere alkaline phosphatase, β-glucosidase and β-glucosaminidase enzymes, to obtain a more complete picture of the combined effect of biostimulants and species. We found that the Bistep biostimulant had an outstanding effect on the leaf tissue culture results of the variety. The transpiration and evapotranspiration findings also confirmed the efficacy of biostimulants. In the case of POD activity and rhizosphere enzyme measurements, Bistep and Yeald Plus obtained statistically higher values than the control group. Kelpak produced better results than the control group in several measurements (alkaline phosphatase levels; evapotranspiration results), but in other cases it resulted in lower values than the control treatment. The use of Bistep and Yeald Plus can greatly assist growers in the cultivation of V. opulus ‘Roseum’ in an urban environment.