Table II.
Results of the refinement of the EXAFS spectra using the Excurve98 program
The graphs of the fits for young leaves are shown in Figures 2 and 3, and those of all other samples are displayed in the figures of the supplemental material. For the samples Zn His and Cd glutathione, the lower no. of ligands results in a slightly better FI. On the basis of an EXAFS analysis, the difference between five and six ligands cannot be distinguished. Similarly, when two different distances were refined for O and N, no significant improvement was found. EF, Fermi energy, defines the threshold for the EXAFS spectra (Rehr and Albers, 2000). This value was refined for every sample. se, Mathematical ses of the refinement (two sigma level). The error of the EXAFS approach as such is higher, about 10% for the proportions, 1 for the no. of total ligands, and 0.01 Å for the interatomic distances. This is revealed by the differences between samples of the same type, shown here for the Cd edge of young and mature leaves, 100 μm Cd + 10 μm Zn.
| Sample | No. of Ligands (±se) | Distance (±se) | σi2 (±se) | EF (±se) | FI × k3 (±se) |
|---|---|---|---|---|---|
| Å | Å2 | ||||
| Zn K edge | |||||
| Young leaves, 100 μm Cd + 10 μm Zn | 4.1 (±0.3) O | 2.069 (±0.004) | 0.0070 (±0.004) | 9669.7 (±0.5) | 0.30 |
| 1.9 (± 0.3) His | |||||
| Mature leaves, 100 μm Cd + 10 μm Zn | 4.2 (±0.4) O | 2.069 (±0.004) | 0.0064 (±0.004) | 9669.5 (±0.6) | 0.39 |
| 1.8 (±0.4) His | |||||
| Mature leaves, 0 μm Cd + 10 μm Zn | 4.1 (±0.5) O | 2.050 (±0.006) | 0.0082 (±0.006) | 9669.2 (±0.7) | 0.63a |
| 1.9 (± 0.5) His | |||||
| Dead leaves, 100 μm Cd + 10 μm Zn | 2.5 (±0.3) O | 2.049 (±0.006) | 0.0110 (±0.006) | 9668.8 (±0.6) | 0.50 |
| 3.5 (± 0.3) His | |||||
| Mature petioles, 100 μm Cd + 10 μm Zn | 3.4 (±0.4) O | 2.070 (±0.005) | 0.0085 (±0.005) | 9669.0 (±0.6) | 0.44 |
| 2.6 (±0.4) His | |||||
| Mature stems, 100 μm Cd + 10 μm Zn | 2.9 (±0.4) O | 2.056 (±0.006) | 0.0093 (±0.006) | 9669.0 (±0.7) | 0.56 |
| 3.1 (±0.4) His | |||||
| Mature stems, 0 μm Cd + 10 μm Zn | 2.9 (±0.9) O | 2.060 (±0.013) | 0.0092 (±0.012) | 9669.0 (±1.3) | 1.09a |
| 3.1 (±0.9) His | |||||
| Cd K edge | |||||
| Young leaves, 100 μm Cd + 10 μm Zn | 1.5 S | 2.51 (±0.01) | 0.008 (±0.0005) | 26,714.7 (±0.8) | 0.16 |
| 4.5 (±0.2) N/O | 2.28 (±0.01) | ||||
| See above, second sample | 1.6 S | 2.49 (±0.006) | 0.009 (±0.0005) | 26,716.0 (±1.5) | 0.26 |
| 4.4 (±0.4) N/O | 2.29 (±0.01) | ||||
| Mature leaves, 100 μm Cd + 10 μm Zn | 1.5 S | 2.50 (±0.01) | 0.010 (±0.0005) | 26,714.9 (±1.1) | 0.29 |
| 4.5 (±0.3) N/O | 2.28 (±0.01) | ||||
| See above, second sample | 1.1 S | 2.43 (±0.01) | 0.010 (±0.0005) | 26,717.8 (±0.7) | 0.34 |
| 4.9 (±0.2) N/O | 2.32 (±0.005) | ||||
| Mature leaves, 50 μm Cd + 10 μm Zn | 1.4 S | 2.46 (±0.02) | 0.011 (±0.001) | 26,716.8 (±1.4) | 0.42 |
| 4.6 (±0.3) N/O | 2.31 (±0.01) | ||||
| Senescent leaves, 100 μm Cd + 10 μm Zn | 0.3 S | 2.47 (±0.07) | 0.007 (±0.0005) | 26,717.1 (±1.7) | 0.74 |
| 5.7 (±0.4) N/O | 2.28 (±0.01) | ||||
| Dead leaves, 100 μm Cd + 10 μm Zn | 0.7 S | 2.49 (±0.02) | 0.010 (±0.0005) | 26,716.0 (±1.0) | 0.42 |
| 5.3 (±0.3) N/O | 2.29 (±0.01) | ||||
| Mature petioles, 100 μm Cd + 10 μm Zn | 3.1 S | 2.49 (±0.01) | 0.010 (±0.0005) | 26,711.0 (±0.7) | 0.53 |
| 2.9 (±0.1) N/O | 2.25 (±0.01) | ||||
| Senescent petioles, 100 μm Cd + 10 μm Zn | 0.9 S | 2.49 (±0.010) | 0.008 (±0.0005) | 26,717.2 (±0.8) | 0.18 |
| 5.1 (±0.2) N/O | 2.29 (±0.006) | ||||
| Mature stems, 100 μm Cd + 10 μm Zn | 2.3 S | 2.50 (±0.01) | 0.009 (±0.0005) | 26,713.2 (±1.3) | 0.23 |
| 3.7 (±0.3) N/O | 2.28 (±0.01) | ||||
| Senescent stems, 100 μm Cd + 10 μm Zn | 1.5 S | 2.49 (±0.01) | 0.010 (±0.0005) | 26,715.9 (±1.7) | 0.42 |
| 4.5 (±0.5) N/O | 2.29 (±0.01) |
FI is higher due to the lower signal to noise ratio of the measured data.