Sentence:  The specific staining by both direct and indirect methods showed that WTV antigen was concentrated in the pseudophloem tissue and in a few thick walled cells in the xylem region , but was not detectable in any other tissues of the <WSD>root</WSD> and stem tumors . 
Meaning of the word marked with <WSD> tags:  (botany) the usually underground organ that lacks buds or leaves or nodes; absorbs water and mineral salts; usually it anchors the plant to the ground