The morphology of maize roots transformed with Agrobacterium rhizogenes strain K599 harbouring a GFP reporter gene construct. Figures A and B show transformed maize roots in phytotrays and C shows a transformed root in a rhizotron under bright field (left column) and UV irradiance (right column). (A) Tumours that formed 10 days after infection with A. rhizogenes, from which hairy roots emerge. (B) Highly transgenic hairy roots that formed from wounded sites (15 days after inoculation with A. rhizogenes). (C) Transgenic roots that sometimes formed along with wild type roots. Composite plants consisted of a mosaic of transformed roots that expressed GFP (T) and wild type (WT) from normal maize growth that did not show GFP expression. GFP fluorescence can also be seen on an emerging root at the point labelled ‘E’.