Meristematic tissues are virus free because:
Meristematic tissues remain virus free because virus multiplication and movement are inhibited in rapidly dividing apical dome cells. Most plant viruses rely on plasmodesmata intercellular connections and phloem sieve tubes for systemic translocation from source leaves to sinks; meristem dome lacks differentiated phloem and contains narrow plasmodesmata with high callose deposition limiting viral cell to cell trafficking. Additionally mitotic cycle of meristem cells is significantly shorter than time required for virus replication and assembly, so daughter cells produced outrun infection front
Ref: Cassells 1991 virus free meristem; Lodish Chap. 8 viral movement.
