Table III.

Nickel coordination by His ligands in T. goesingense and T. arvense measured by x-ray absorption spectroscopy

Time (d)T. goesingenseT. arvense
mmol kg−1dry biomass
10.2  (3.0)3-a 2.5  (8.7)0.4  (0.5)2.9  (6.2)
30.1  (4.2)2.5  (6.7)1.0  (2.3)3.9  (10.6)
50.4  (6.5)2.6  (8.1)1.2  (2.4)4.3  (13.0)
70.2  (5.3)4.1  (9.4)1.3  (3.3)6.1  (14.8)

Values in parentheses represent the total Ni content of the tissue mmol kg−1 dry biomass.

    • F3-a Plants were exposed to 10 μmNi(NO3)2 in the hydroponic solution. By fitting x-ray absorption spectra of aqueous Ni2+ and Ni2+ coordinated with His: 6.66 mmNi(NO3)2, 80 mm His, 30% (w/v) glycerol, pH 7.0; citrate: 6.66 mmNi(NO3)2, 70 mm citrate, 30% glycerol, pH 8.0; Gln: 1 mmNi(NO3)2, 4 mm Gln, 30% glycerol, pH 7.3; and isolated T. goesingense shoot cell wall material (Lasat et al., 1996), we were able to determine the percentage contribution of His as a ligand of Ni2+. Total Ni content of the tissues was analyzed by inductively coupled plasma emission spectroscopy and this was used to calculate the absolute amount of Ni coordinated by His in the tissues. The values represent data collected from a single plant sample at each time point, and each x-ray spectrum used for the fits represents the mean of three independent scans, each being composed of data acquired from 13 independent detectors.