Many plant species can adapt to flooding and hypoxia by forming a root system with an altered architecture: thicker, shorter and shallower adventitious roots, than under aerated conditions. The internal gas transport is often improved by increased root porosity and aerenchyma, which is tissue with large intercellular spaces. The raised root aeration allows better supply of oxygen to plant tissues and diffusion of oxygen into the rhizosphere (Radial Oxygen Loss, ROL). This phenomenon creates narrow, but well aerated zones in the hypoxic soil, where phytotoxins are oxidised and methanotrophic as well as nitrifying bacteria can live. The aim of the study was to determine the change of root architecture, porosity and ROL from roots of Plantago lanceolata plants originating from The Middle Vistula River Gorge. Selected plant species were subjected to transient flooding during 7 days of cultivation on aerated and stagnant oxygen-deficient hydroponic medium. We observed the formation of shorter hypoxic, adventitious roots (56-69 mm) than control roots (112-196 mm) with high porosity (stagnant 15-21 %, control 8.5-9.4%), and the diameter of aerated zone (halo) increased from control values of 0-1.5 mm to 2-2.5 mm under hypoxic conditions.