Garden Post-Transplant Effects of Pre-Transplant Plug Cell Volume and Growing Medium Quality (as Abiotic Stresses) in Impatiens Walleriana

Although much is known about the production of bedding plants, including Impatiens walleriana, little has been documented on their post-production performance. Thus, the aim of this work was to understand how pre-transplant crop management related to root restrictions imposed by plug cell volume and substrate quality affects the post-production performance related to biomass accumulation. To this end, we tested four plug cell volumes, as well as four growing media with significantly different physical and chemical properties, during nursery and pot culture. We also evaluated the difference between use and nonuse of synthetic cytokinin spray (benzyl aminopurine, BAP), a proven stress alleviator. Our novelty data validated the previous hypothesis and showed that plant quality and garden performance are dependent on these potential stress sources. The physiological mechanisms involved included differences in leaf area expansion (estimated mainly by relative leaf area expansion rate) and differences in CO2 fixation capacity (estimated by net assimilation rate). The sum of these responses determined significant differences in total fresh and dry weight during pot culture, which were amplified when plants were transplanted to a field bed. Spraying plants with synthetic cytokinin early during nursery allowed overriding of most root restriction abiotic stresses related to plug cell volume and growing media; therefore, synthetic cytokinin constitutes a tool to improve the yield of bedding plants (at the grower’s level) and garden performance.