PYRIDINE-NUCLEOTIDE CONTENTS AND ACTIVITY OF PROTOCHLOROPHYLLIDE PHOTOOXIDOREDUCTASE IN-VIVO .2. COMPARATIVE INVESTIGATIONS IN PROTOPLASTS AND ETIOPLASTS OF AVENA-SATIVA L DURING GREENING

Etiolated oat mesophyll protoplasts and etioplasts released from etiol ated protoplasts were able to perform protochlorophyllide (PChlide) re duction but showed a high amount of inactive P-633/628, compared with intact leaves. In spite of this, the. anabolic reduction charge (ARC, NAPDH+H+/NADP(+) + NADPH+H+) was maintained at 0.66 - 0.77 up to 30 mi n of irradiation with weak ''white light'' (10 W m(-2)). This indicate d a high buffering capacity of the isolated system to provide NADPH+H, only at the expense of internal reserves. A change in the redox stat e of the NADP(+)/NADPH+H+ couple during protochlorophyllide reduction was not observed in etioplasts. The resulting redox potential was in t he range of -330 mV optimal for protochlorophyllide reduction.