TY - Generic T1 - Physiological effects of long term exposure to low concentrations of SO2 and NH3 on poplar leaves. Y1 - 1991 A1 - van Hove, L.W.A. A1 - van Kooten, O. A1 - van Wijk, K.J A1 - Vredenberg, W.J. A1 - Adema, E.H. A1 - Pieters, G.A. JF - Plant Physiology VL - 82 ER -