Table 2.
Estimated concentrations of Fe, Zn, and Cu in the cell and in the phloem sap and affinity constants (Kd) for the formation of the indicated metal-ligand complexes.
| Fe2+ | Zn2+ | Cu2+ | |
|---|---|---|---|
| Cytoplasmic concentration (M) | 10-6 Kruszewski, 2004 | 10-11; 10-12 Silva and Williams, 2001; Bozym et al., 2006; 0.4 × 10-9 Lanquar et al., 2014 |
10-15; <10-18 Silva and Williams, 2001; Kuchar and Hausinger, 2004 |
| Phloem sap concentration (M) | 1.7 × 10-4 Marschner, 1995 | 2.4 × 10-4 Marschner, 1995 |
1.9 × 10-5 Marschner, 1995 |
| Xylem sap concentration (M) | 10-5 Marschner, 1995 | 2 × 10-5 Marschner, 1995 |
1.7 × 10-6 Marschner, 1995 |
| Log Kd (NA) | 12.1 Callahan et al., 2006 | 14.7/15.4 Callahan et al., 2006 | 18.6 Callahan et al., 2006 |
| Log Kd (GSH) | 5.1 Hider and Kong, (2011) | 12.5 Martell and Smith, 1974 for ML2/M.L2 |
19.9∗ Martell and Smith, 1974 for M(HL)2/M.(HL)2 |
| Log Kd (citrate) | 4.4 Callahan et al., 2006 | 5.0 Callahan et al., 2006 | 5.9 Callahan et al., 2006 |
We note that the precise concentration of kinetically labile elements in the plant cell has not been documented except for Zn (Lanquar et al., 2014). Data are compiled based on indicated reports and so these values may differ considerably between organisms, cells, and cellular compartments, and as a result of the different analytical methods and conditions that have been employed.
∗The stability constant was enumerated for Cu+.