Effects of Iron and Oxygen on Chlorophyll Biosynthesis: I

Corn ( Zea mays , L.), bean ( Phaseolus vulgaris L.), barley ( Hordeum vulgare L.), spinach ( Spinacia oleracea L.), and sugarbeet ( Beta vulgaris L.) grown under iron deficiency, and Potamogeton pectinatus L, and Potamogeton nodosus Poir. grown under oxygen deficiency, contained less chlorophyll than the controls, but accumulated Mg-protoporphyrin IX and/or Mg-protoporphyrin IX monomethyl ester. No significant accumulation of these intermediates was detected in the controls or in the tissue of plants stressed by S, Mg, N deficiency, or by prolonged dark treatment. Treatment of normal plant tissue with δ-aminolevulinic acid in the dark resulted in the accumulation of protochlorophyllide. If this treatment was carried out under conditions of iron or oxygen deficiency, less protochlorophyllide was formed, but a significant amount of Mg-protoporphyrin IX and Mg-protoporphyrin IX monomethyl ester accumulated. These results are consistent with the presence of an O 2 , Fe-requiring step between Mg-protoporphyrin IX monomethyl ester and protochlorophyllide.