McLeod Kenneth W, Ciravolo Thomas G
Savannah River Ecology Laboratory, University of Georgia, PO Drawer E, Aiken, South Carolina 29802, USA.
Environ Toxicol Chem. 2003 Dec;22(12):2948-51. doi: 10.1897/02-457.
In anaerobic soils of wetlands, Mn is highly available to plants because of the decreasing redox potential and pH of flooded soil. When growing adjacent to each another in wetland forests, water tupelo (Nyssa aquatica L.) had 10 times greater leaf manganese concentration than bald cypress (Taxodium distichum [L.] Richard). This interspecific difference was examined over a range of manganese-enriched soil conditions in a greenhouse experiment. Water tupelo and bald cypress seedlings were grown in fertilized potting soil enriched with 0, 40, 80, 160, 240, 320, and 400 mg Mn/L of soil and kept at saturated to slightly flooded conditions. Leaf Mn concentration was greater in water tupelo than bald cypress for all but the highest Mn addition treatment. Growth of water tupelo seedlings was adversely affected in treatments greater than 160 mg Mn/L. Total biomass of water tupelo in the highest Mn treatment was less than 50% of the control. At low levels of added Mn, bald cypress was able to restrict uptake of Mn at the roots with resulting low leaf Mn concentrations. Once that root restriction was exceeded, Mn concentration in bald cypress leaves increased greatly with treatment; that is, the highest treatment was 40 times greater than control (4,603 vs 100 microg/g, respectively), but biomass of bald cypress was unaffected by manganese additions. Bald cypress, a tree that does not naturally accumulate manganese, does so under manganese-enriched conditions and without biomass reduction in contrast to water tupelo, which is severely affected by higher soil Mn concentrations. Thus, bald cypress would be less affected by increased manganese availability in swamps receiving acidic inputs such as acid mine drainage, acid rain, or oxidization of pyritic soils.
在湿地的厌氧土壤中，由于淹水土壤的氧化还原电位和pH值降低，锰对植物具有很高的有效性。在湿地森林中相邻生长时，水紫树（Nyssa aquatica L.）叶片中的锰浓度比落羽杉（Taxodium distichum [L.] Richard）高10倍。在温室实验中，在一系列富锰土壤条件下研究了这种种间差异。水紫树和落羽杉幼苗种植在添加了0、40、80、160、240、320和400 mg Mn/L土壤的施肥盆栽土壤中，并保持在饱和至微淹条件下。除了最高锰添加处理外，水紫树叶片中的锰浓度均高于落羽杉。在锰添加量大于160 mg/L的处理中，水紫树幼苗的生长受到不利影响。最高锰处理下水紫树的总生物量不到对照的50%。在低水平添加锰时，落羽杉能够在根部限制锰的吸收，从而使叶片中的锰浓度较低。一旦超过根部的限制，落羽杉叶片中的锰浓度会随着处理而大幅增加；也就是说，最高处理浓度比对照高40倍（分别为4603和100 μg/g），但落羽杉的生物量不受锰添加的影响。落羽杉是一种不会自然积累锰的树木，在富锰条件下会积累锰，且生物量不会减少，这与水紫树形成对比，水紫树会受到较高土壤锰浓度的严重影响。因此，在接受酸性输入（如酸性矿山排水、酸雨或黄铁矿土壤氧化）的沼泽中，落羽杉受锰有效性增加的影响较小。
