In the vermiculite culture system,
7 d after inoculation
with GFP-tagged W19 cells,
the root system
was examined by CLSM to assess the presence of bacterial
cells. The result showed that GFP-tagged W19
cells were not observed in CK1 treatment (Fig. 4a, d),
and few cells were observed in CK2 treatment (indicated
by arrows) (Fig. 4b, e). The GFP-tagged W19 cells
could be easily distinguished from the background fluorescence
of the strain-inoculated living banana roots (T
treatment) (Fig. 4c, f), indicating that root exudates
from living plants play an important role in the colonization
by the PGPR strain. The calculated results
showed that the bacterial population remained at 8.7
106 CFU g−1 root DW on the treated roots.