Mechanism of Flood Tolerance in Reed, Phragmites australis (Cav.) Trin. ex Steudel

Important factors, such as porosity, respirational O2consumption, O2release of the roots and iron oxidation on the root surface, which are involved in the flood tolerance of Phragmites australis were investigated in northern Germany. The porosity of the different organs was determined as 58% for rhizomes, 42% for culms and 23-38% for adventitious roots. Mean respirational O2consumption of below ground organs was measured at 5, 10, 15 and 20⚬C as respectively 0.25, 0.5, 0.8 and 1.75 nmol O2g-1dry mass s-1. The saturation concentration was estimated to be less than 0.017 mmol O2l-1up to 15⚬C and 0.03 mmol O2l-1at 20⚬C. From values of the root O2gas exchange obtained from entire plants predictions are made concerning the O2status of the roots under field conditions throughout the year. The O2release for a reed stand was calculated as 65-129 mg O2m-2h-1in summer conditions. The oxidation power of the roots was further demonstrated by the development of iron hydroxideplaques on the root surface.