Distribution of Cesium and Cationic Mineral Elements in Napiergrass

Napiergrass is fast-growing perennial known for its high potential for accumulation of cesium (Cs). Cs is highly mobile within a plant and can be distributed to various plant organs. Here, we investigated the distribution of cesium-133 ( 133 Cs) and competitively translocated cationic minerals, such as potassium (K), calcium (Ca), and magnesium (Mg), in different organs of napiergrass. Treatments comprised four concentrations of 133 Cs applied to soil: 0 (as control); 300; 500; and 1000 μM. Leaf blades contained significantly higher concentrations of 133 Cs than stems under 300 and 500 μM 133 Cs treatments ( P < 0.01). Specifically, significantly greater 133 Cs content was measured in younger parts of stems and leaf blades compared with mature or older plant parts. The 133 Cs content in younger parts was 5302, 13,059, and 51,678 mg kg −1 in stems and 6961, 16,363, and 52,781 mg kg −1 in leaf blades under 300, 500, and 1000 μM 133 Cs treatments, respectively. Distribution ratios of K were higher in stems than in leaf blades in all 133 Cs-treated conditions ( P < 0.05). A significantly negative correlation was found between K and Ca or Mg in leaf blades, suggesting that 133 Cs and K are similarly competitive with Ca or Mg within napiergrass. We conclude that 133 Cs is distributed to younger plant parts, especially leaf blades, and that translocation of Ca and Mg is strongly inhibited by the presence of 133 Cs or K within organs. This suggests that 133 Cs or K can inhibit Mg translocation and could lead to Mg deficiency in younger plant parts.