Possesses xyloglucan endotransglucosylase (XET) activity in vitro. Does not possess xyloglucan endohydrolysis (XEH) activity (PubMed:20732879). Cleaves and religates xyloglucan polymers, an essential constituent of the primary cell wall, and thereby participates in cell wall construction of growing tissues (PubMed:23585673). Involved in cell proliferation in the tissue reunion process of wounded inflorescence stems. Maybe a downstream target of NAC071 as a consequence of auxin action in wounded stems (PubMed:25182467). breaks a beta-(1->4) bond in the backbone of a xyloglucan and transfers the xyloglucanyl segment on to O-4 of the non-reducing terminal glucose residue of an acceptor, which can be a xyloglucan or an oligosaccharide of xyloglucan. Optimum pH is 7.0. Root specific. By auxin. Contains at least one intrachain disulfide bond essential for its enzymatic activity. Belongs to the glycosyl hydrolase 16 family. XTH group 2 subfamily.