THE INOCULATION OF TOBACCO CALLUS TISSUE WITH TOBACCO MOSAIC VIRUS

Although cultures of normal and conditioned tobacco callus tissue occasionally became infected when dilute solutions of tobacco mosaic virus was poured over them, injuries were usually required, and the number of infections depended on the type and number of injuries. Tissues infected by superficial injuries usually became virus-free after subculturing, whereas those infected by needle-prick remained infected permanently. Although no plasmodesmata were found joining cells in the tissue cultures, tobacco mosaic virus moved between them at a rate of about 1 mm. per week, approximately the same rate as it moves through cells of the leaf parenchyma.