Effects of cadmium on the behaviour of citric acid in isolated tomato xylem cell walls
M.H.M.N. Senden1, A.J.G.M. Vand der Meer, T.G. Verburg and H.Th. Woltetbeek
Journal of Experimental Botany Volume 45, Number 5 Pp. 597-606
http://jxb.oxfordjournals.org/cgi/content/abstract/45/5/597