The oxygen diffusion resistance of Lupinus albus (L.) cv. Multolupa root nodules was increased by subjection to short-term stresses; lowering rhizosphere temperature from 25 to 16 °C (2 h), detopping plants (3 h), darkening plants (21 h) or exposing roots to 20 mol m−3 KN03 for 2, 4 or 6 d. Microscopic observations and measurements showed that this resulted in the area of open intercellular spaces within the inner cortex being reduced due to both cell expansion and increased production of an occluding glycoprotein. Electrophoretic and Western Blot analysis using the monoclonal antibodies MAC236 and MAC265 showed two distinct glycoprotein antigens with molecular weights of 240 and 135 kDa, respectively. Both antigens are localized within intercellular spaces of the inner cortex. The amount of glycoprotein was determined using either ELISA, with MAC265, or quantification of immunolabelling with MAC236. This immunolabelling also localized the glycoprotein within globules adhering to the inside of the inner cortical cell walls.