Abstract
Multiplication and distribution of viruses in the stem tissues adjacent to the apical meristem of infected plants was studied by the fluorescent antibody technique and electron microscope observation. Combinations of viruses and plants used Were: tobacco mosaic virus-petunia, tobacco and tomato; cucumber mosaic virus-tobacco, petunia and cucumber: potato virus X-tobacco, potato, Nicotiana glutinosa and Datura stramonium; potato virus Y-tobacco and potato. In any combinations of virus and plant tested, no virus was detected in the apical meristem, in the region close to the base of meristem Where the tissue remained to be differentiated and in the very young leaf primordia on an early stage after generation from regions adjacent to the meristem. Virus was detected in the regions located below such parts, where tissue differentiation was considerably advanced. The virus content successively increased from less differentiated cells to move differentiated ones. In the leaf primordia, virus was first detected in the phloem when the vascular bundle became differentiated, and then spread to the lamina as the primordia grew.
