Response of the ornamental bedding plant Impatiens walleriana to plug cell volume on a floating system during nursery

Abstract In ornamental plants, the need to optimize nursery management has led to a tendency to decrease plug cell tray volume. However, in ornamental plants such as Impatiens walleriana, a lower plug cell volume can negatively affect leaf area expansion and biomass accumulation during the pre-transplant cycle. Because these results have been associated with a decrease in root growth, a floating system where roots come out of the plug cell has been proposed. The aim of this work was to describe pre-transplant biomass accumulation in plants from different plug cell volumes and the response to two propagation systems: media-based plug cell trays and floating system. The relationship found between plug cell volume and growth in both the media-based and floating systems is in agreement with that found in previous reports. With respect to the traditional media-based system, the floating system showed higher leaf area expansion, as a result of higher leaf appearance rate and relative leaf area expansion. Higher fresh and dry weight accumulation were estimated through the relative growth rate (RGR), with a strong relationship with the capacity of photo assimilate production (net assimilation rate) and RGR. However, all these changes cannot be exclusively associated with a higher root growth in the floating system. Our experiments validate the positive results in favor of the use of a floating system and also shows the physiological mechanisms involved.