ABSTRACT
Results from experiments with Potamogeton pectinatus L. grown in an artificial substrate amended with various combinations of peat and glucose or sucrose suggest that plant weight and the number and weight of tubers produced per plant increased significantly when plants were grown in sediment amended with peat. Contrary to expectations, the addition of labile organic components, glucose or sucrose, to the substrate (up to 15%, w/w) did not influence plant growth. Plants grown in sediment amended with peat had higher levels of tissue Fe. The weight of tubers produced per gram of non tuber tissue was not influenced by sediment properties. These results support the hypothesis that the mechanism by which sediment organic matter affects macrophyte growth is by altering sediment density.