Table I.

Rates of tetrapyrrole synthesis and levels of tetrapyrroles in soybean tissues

TissueCoprogen OxidaseRate of Tetrapyrrole SynthesisHemeChlorophyll
nmol h−1 g−1 fresh wtnmol g−1 fresh wt
Nodules 21 d after infection108.2  ± 9.258.6  ± 8.9
Nodules 28 d after infection81.4  ± 6.20.73181.5  ± 10.3
24-h Greened leaves35.0  ± 4.8388.9  ± 23.0
48-h Greened leaves15.9  ± 1.626.9955.6  ± 16.5
Newly emerged leaves38.9  ± 1.82330.0  ± 58.9
Fully expanded leaves16.6  ± 0.23.32890.0  ± 89.5

Soybean plants were grown as described in Methods. For the measurement of heme synthesis during nodulation, they were grown in a greenhouse for 14 d before infection with B. japonicum. For chlorophyll synthesis during greening, plants were grown in complete darkness for 7 d and then exposed to continuous illumination. The rate was determined between 24 and 48 h, in the exponential phase. For chlorophyll synthesis during leaf expansion of light-grown plants, samples of leaves were taken at the newly emerged stage and then again when they were fully expanded (7 d later). The enzyme activity values are the means ± se of four samples, and those for heme and chlorophyll are the means of three samples.