Direct addition of P. koreensis 2.74 in its spent broth, reducing
the need for centrifugation and washing of the cells, was observed
to be less favourable, causing a significant reduction in plant
weight. Potentially this could be due to the presence of phytotoxic
secondary metabolites produced by P. koreensis 2.74 in the broth.
However, also the treatment which received broth in which no cells
had been cultured showed reduced plant weight. There may be
several reasons for this effect such as a negative impact on the
composition of the nutrient solution when the mediawas added, or
that the increased content of organic carbon allowed proliferation
of a deleterious microflora.