“…Generally, local movement is a relatively slow process (e.g., 5-15 µm/h, see Gibbs 1976), presumably restricted by the rate of viral replication. In contrast, long-distance movement through the vascular system is rather rapid (e.g., 50-80 mm/h (see Gibbs 1976), as it occurs with the flow of photoassimilates and, in some Barker et al 1986;Derrick et al 1992Derrick et al , 1997 PepMoV-FL Resistant pepper strain Guerini et al 1999 a In susceptible hosts, the indicated viruses, except for PLRV, move from non-vascular ME to different vascular-associated and vascular cell types (BS, VP, CC, SE) of the inoculated leaves and, through SE, to systemic leaves, which they first enter through the vasculature and then unload into ME. In restrictive hosts, viral movement is arrested at different cellular boundaries, which usually are specific for a host-viral strain combination as shown in this Table. Arrows mark the cell types between which the indicated viral strain can move in the corresponding restrictive host, and solid vertical lines indicate the cell boundaries at which the viral movement is arrested Spread Throughout the Plant: Systemic Transport of Viruses 87 cases, does not require viral replication (Susi et al 1999;Wintermantel et al 1997).…”