Responses of Pansy (Viola wittrockiana Gams.) to the Quality of the Growing Media

The quality of the growing medium stands out as one of the most important factors affecting the success of annual plants, especially when grown in potted culture. Recently, we have suggested that growing medium gives not only a matrix for water and nutrient absorption but also a source of external signalling. The aim of this work was to assess the performance of six pansy (Viola wittrockiana Gams.) genotypes grown in two growing media with significant differences in both physical and chemical properties, aiming to understand how substrate quality change the physiological mechanism related to biomass accumulation. The responses of the six pansy genotypes tested to the two growing media were significantly different. The mechanisms involved included fresh weight accumulation, leaf area expansion; RGR, RLA, glucose content and photo assimilate partitioning. On the other hand, RGR, RLA and glucose content were associated with root dry weight at the end of the experiments. Since the responses to the different growing media were the same as those found in plants grown with root restriction related to container volume, we speculated that cytokinins might act as endogenous signals.