Comparison of Iron Plaque Characterization and Associated Elements on the Surface of Lotus Rhizomes

Ten lotus (Nelumbo nucifera Gaertn.) cultivars were used to investigate the amounts and chemical composition of iron plaque on the rhizome surface. Iron formed a continuous precipitate on the rhizome surface. ‘Jiantoubaihe’ had the largest amounts of total Fe on the surface of the lotus rhizomes, followed by ‘Elian No.6’ and ‘Wenzhoushangdongou’, with ‘Elian No.7’ and ‘Suzhouhuaou’ having the least total Fe. Most of the total Fe was Fe (Ⅲ) (64.1%-85.8%), with a small percentage of Fe (Ⅱ) (14.2%-35.9%). Scanning electron micrographs (SEM) demonstrated that the iron plaque was unevenly distributed on the rhizome surface, and had a porous or flocculent structure. Energy dispersive X-ray (EDX) showed that the iron plaque mainly contained Fe, C, O, Al and Si. In addition K, P and Ca were also detected on the rhizome surface of ‘Jiantoubaihe’. Among the ten cultivars, ‘Elian No.7’ and ‘Suzhouhuaou’ formed the thinnest iron plaque.