Influence of Different Container Typology on Ulmus minor Plant Growth and Root Morphology

Plants grown in standard plastic containers for a long time result in deformed roots. This experiment investigated the effect of different container types on growth and root morphology of Ulmus minor Mill. In April 2008 one-year-old bare-root seedlings were potted in the following 0.9-L containers: Superoots® Air-CellTM (Caledonian Tree Company, UK), Quadro fondo rete (Bamaplast, IT) and smoothsided containers. At the beginning of the second growing season the same plants were re-potted in the following 3.0-L containers: Superoots® Air-PotTM (Caledonian Tree Company, UK); Quadro antispiralizzante (Bamaplast, IT) and smooth-sided containers. Air-PotTM and Air-CellTM were characterized by cuspated walls made up of closed inward pointing cones and open ended outward pointing cones, while Quadro fondo rete and Quadro antispiralizzante were characterized by vertical interior ribs on the container walls. The trial was carried out in an experimental nursery located at the Fondazione Minoprio (Como, Italy). At the end of each growing season shoot and root dry weight were measured and root morphology was studied. Chlorophyll fluorescence and leaf chlorophyll content were measured during the second growing season. At the end the of first growing season plants grown in traditional plastic container showed a poorest root conformation, while no differences were observed between Superoots® Air-CellTM and Quadro fondo rete. At the end of the second year plants grown in Superoots® Air-PotTM had lower root deformation compared with plants grown in Quadro antispiralizzante and smooth sided containers. Faster leaf senescence was observed in plants grown in Air-PotTM containers compared to the plants grown in the smooth-sided container.