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 <WSD>was</WSD> not detectable in any other tissues of the root and stem tumors . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)