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 root and <WSD>stem</WSD> tumors . 
Meaning of the word marked with <WSD> tags:  a slender or elongated structure that supports a plant or fungus or a plant part or plant organ