to . 



E 

 E 



Q> 

 O 



3 



O 



Cl 

 CM 



8 12 

 Minutes 



Figure 4. Effect of metals on reversal of o-phenanthroline (o-P) inhibi- 

 tion of sugar beet chloroplasts. o-Phenanthroline was added to chloroplast 

 fragments in all cases except to the control represented by Curve I. Curve 

 II, effect of adding nickel and cobalt and doubling the copper concentra- 

 tion; Curve III, effect of zinc; Curve IV, effect of copper; Curve V, effect 

 of iron (ferrous); Curve VI, o-phenanthroline alone. The addition of 

 chromate was without effect. The concentration of o-P was 5 X io~ 5 M. 

 The metals were added as sulfates and nitrates in a 5/3 X io — 5 M con- 

 centration to give a stoichiometric ratio of 3 o-P: 1 metal. Conditions not 

 specified were the same as those given in legend for Figure 1. 



