A plant structure (PO:0009011) that consists predominantly of similarly specialized plant cells (PO:0009002) of one or more types. [source: POC:curators, TAIR:Leonore_Reiser]
Comment
A portion of plant tissue may contain one or several types of cells that are organized in a specific spatial arrangement into a structural unit (which includes a mass of callus) and may include an intercellular matrix. May include other types of isolated cells, such as idioblasts.