Root Restriction Effects on the Bedding Pot Plant Impatiens walleriana

Pot plant growers must take two technological critical decisions: the pre-transplant plug-cell size and the post-transplant growing medium, both of which have been mentioned as abiotic stress sources for bedding pot plants, including Impatiens walleriana. However, only a few recent reports in bedding pot plants have simultaneously included limiting and non-limiting plug cell volumes and growing medium. The aim of this work was to evaluate the response of a wide range of these two abiotic stress sources on I. walleriana plant growth on the assumption that the responses are mainly associated with a negative hormonal signaling from roots and that these can be overridden by a pre-transplant benzyl aminopurine (BAP) spray. The main result was that, in I. walleriana plants, the abiotic stresses imposed by the plug cell volume and growing medium quality constitute an interactive process associated with cytokinins synthesis. From a grower´s point of view, one expensive option to avoid root restriction is to increase the plug cell volume and the growing medium quality. In contrast, a single 100 mg l-1 BAP spray can partially override the root restriction symptoms.