186 



Achim Trebst, Herbert Eck and Sieglinde Wagner 



(36) 



In detergent treated chloroplasts ascorbic acid photooxidation is enhanced 



and not anymore inhibited by o-phenanthroline(^9)^ but the photooxidation of 

 o-hydroquinone is completely inactivated(3o) . 



salicylaldoxime 

 treated 



P P 



^ls3 Isl 



additions (o, 1 ^mol) to O2 H2O2 O^ H2O2 

 lo ^mol ascorbate uptake formed uptake formed 

 ^atoms fxmoles ^atoms ^moles 



+ vitamin K3 11,4 5,7 5,2 2,3 



+ vitamin K3 + lo~'*m DC MU o,7 o, 1 4,6 2,3 



+ anthraquinone sulfonate 12,9 5,7 5,7 3,1 

 + anthraquinone sulfonate 



+ lo-^m DCMU 0,4 5,6 2,1 



Table lo: Ascorbate photooxidation in normal and salicylaldoxime treated 



chloroplasts (Plgl, containing 4 mg chlorophyll, were suspended 

 in-3 ml cold 5- lo"^m salicylaldoxime, spun down after 2 min, 

 washed once with water and resuspended in 2 ml water. Further 

 treatment as in table 1, 15 min light in air, lo~-^m KCN per vessel). 



^atoms oxygen taken up in 



5 fxmol chlorogenic acid 



" " + lo" m DCMU 



5 ^mol DOPA 



" " + lo" m DCMU 



lo p.mol ascorbate + o, 1 fxmol anthraquinone 



sulfonate 



" " " + lo""^ DCMU 



Table 11: Photooxidation of o-hydroquinones in normal and salicylaldoxime 

 treated chloroplasts (compared with ascorbate oxidation) 

 (conditions as in table lo). 



