Individual plastids of vascular plants have generally been considered
to be discrete autonomous entities that do not directly communicate wi
th each other. However, in transgenic plants in which the plastid stro
ma was labeled with green fluorescent protein (GFP), thin tubular proj
ections emanated from individual plastids and sometimes connected to o
ther plastids. Flow of GFP between interconnected plastids could be ob
served when a single plastid or an interconnecting plastid tubule was
photobleached and the loss of green fluorescence by both plastids was
seen. These tubules allow the exchange of molecules within an interpla
stid communication system, which may facilitate the coordination of pl
astid activities.