The Uptake and Accumulation of P Assessed by DGT/Rhizobox Method
The rhizosphere zone includes the volume of soil or sediment interacting directly and indirectly with the plant roots and the microzone near root with the radial distance from nanometers to centimeters (Hiltner in Arbeiten der Deutschen Landwirtschafts Ge
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The Uptake and Accumulation of P Assessed by DGT/Rhizobox Method
The rhizosphere zone includes the volume of soil or sediment interacting directly and indirectly with the plant roots and the microzone near root with the radial distance from nanometers to centimeters (Hiltner 1904). The rhizosphere environment is as complex as the aboveground part of the plant. The rhizosphere is the interface between root and mineral phases, which has the intricate ecological feedback, chemical interaction, and the interorganism communication. Rhizobox designs, as introduced by Youssef and Chino (1988) and Kuchenbuch and Jungk (1982), consist of a soil/root compartment and one or more adjacent soil compartments that are separated by porous membranes with a mesh width that allows for the exchange of solutes, but does not allow roots to penetrate from the soil/root into the soil compartments. Depending on the mesh width, root hairs may or may not grow into the soil compartment. In this chapter, a rhizobox with three compartments was designed and it was divided by membranes into narrow layers paralleling the root plane. The porous membranes (nylon or fiberglass) restrict particles passing through two layers and permit water and element exchange. DGT can be tested at the precise location in the rhizosphere of the cultivated aquatic plants in rhizoboxes. The DGT measurement and the related calculation can derive CDGT, CE, C0, Croot, Cstem, Cleaf, and P-fractions in sediment, and the P-uptake mechanism by the plant root, and DGT as a proxy to mimic P taken up by plant root, can be investigated and assessed more thoroughly, compared with the results of in situ DGT test at plant rhizosphere in lake.
© Springer Science+Business Media Singapore 2016 S. Wang and Z. Wu, DGT-based Measurement of Phosphorus in Sediment Microzones and Rhizospheres, DOI 10.1007/978-981-10-0721-7_8
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8.1
P-Concentration in Sediment–Porewater–Plant Samples and the Derivation of CE and Rdiff
The DGT test in the rhizoboxes of two aquatic plants was conducted at the floating flat (Fig. 8.1) in Erhai Lake. After the test, DGT concentration (CDGT), porewater concentration (C0), the P-content in plant tissues (root, stem, and leaf), P-content in sediment, and the effective concentration (CE) were determined or calculated. Firstly, P-concentration in sediment, porewater, root, stem, and leaf: DGT concentration, the calculation of CE, and Rdiff for DGT test in rhizobox with Zizania latifolia are introduced in the following contents. The P-contents in root/stem/leaf were above the LOD (Table 3.2 in Chap. 3) and the values of them are indicated in Fig. 8.2. P-fractions in sediments of 15 rhizoboxes are indicated in Fig. 8.3. The P-concentration in porewater (C0), CDGT, and P-fraction (NH4Cl-P + BD-P) in sediments for 2D-DIFS simulation are listed in Table 8.1. The Rdiff is calculated by 2D-DIFS model introduced in Sect. 3.3.1, and the parameters, such as C0 (nmol ml−1), Tc (1010 s), Kd (10−10 cm3 g−1), Pc (g cm−3), D
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