Translocation of tobacco mosaic virus in morphologically different tobacco callus tissues.

Blocks (5×5×15mm) of tobacco callus tissue different in compactness of cell arrangement were inoculated at the top surfaces with tobacco mosaic virus (TMV) by means of needle pricking. The blocks were then periodically separated into 3 segments and the virus concentration in each segment was assayed by half-leaf method on Nicotiana glutinosa. The infection frequency, multiplication rate and translocation velocity of TMV were higher in compact callus as compared to those in soft callus. TMV translocation in compact callus was estimated over 8mm during 10 days after inoculation, while, less than 3mm during 30 days in soft callus. By means of histological observation under electron microscope, the sieve element, perforated sieve plateand plasmodesmata were frequently observed in compact callus, but none of them in soft callus. The rapid decrease of TMV concentration in the rapidly growing soft callus was attributed partially to the poor infection rate, less multiplication, and slow movement of TMV in soft callus tissue.