Table I.

In vitro inactivation of soybean root GS by different MCO systems

Addition	Remaining GS Activity
	% of control with EDTA
Control (buffer only)	100.0
1 mm FeCl3	99.63  ± 0.62
1 mm EDTA	99.98  ± 0.17
1 mm FeCl3/1 mm EDTA	101.89  ± 0.28
5 mm DTT	120.34  ± 4.14
10 mm GSH	125.53  ± 4.00
20 mm ascorbate	122.01  ± 3.15
5 mm DTT/0.125 mm FeCl3	10.10  ± 0.39
5 mm DTT/0.125 mm FeCl3/1 mm EDTA	100.59  ± 0.19
10 mm GSH/0.5 mm FeCl3	24.54  ± 0.12
10 mm GSH/0.5 mm FeCl3/1 mm EDTA	98.90  ± 0.02
20 mm ascorbate/0.5 mm FeCl3	52.22  ± 0.62
20 mm ascorbate/1 mm FeCl3	36.45  ± 0.51
20 mm ascorbate/0.5 mm FeCl3/1 mm EDTA	106.98  ± 0.69

A 4-d-old root extract (desalted ammoniun sulfate fraction) was incubated in 50 mm imidazol (pH 7.4) with FeCl₃ (0.25–1 mm) and either DTT, GSH, or ascorbate in the presence or absence of 1 mm EDTA for 2 h at 4°C, and samples were assayed for transferase activity. Values are the averages ± se of at least three independent experiments and were calculated as the percentages of the remaining activity compared with the control with no addition (n ≥ 3).