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This article in CS

  1. Vol. 13 No. 5, p. 519-524
    Received: Feb 5, 1973

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Distribution and Utilization of 14C-labelled Assimilates in Soybeans1

  1. D. J. Hume and
  2. J. G. Criswell2



Individual soybean [Glycine max (L.) Merr.] plants grown in the field during 2 years were allowed to assimilate 14CO2 either during vegetative growth, at first flowering, at early pod development, or during rapid seed development. Some of the labeled plants were harvested immediately after labelling, and others after 1 week, at incipient leaf drop, or at maturity. Radioactivity was measured in the component parts of each labelled plant.

Plant parts that were growing actively at the tune of labelling accumulated more UC than those parts that were not growing actively. When the plants were growing vegetatively, most of the 14C was incorporated into structural leaf and stem tissue. As labelling tunes became later during ontogeny, stems contained decreasing amounts of 14C, and more 14C accumulated in seeds by maturity. After rapid seed development began, roots and nodules accumulated little 14C.

If plants were labelled before vegetative growth was completed, 30 to 40% of the 14C present immediately after labelling was recovered in plants grown to maturity. Plants labelled during rapid seed development retained 65% of the original 14C at maturity. Calculated losses of 14C due to respiration averaged 20%. Most of the 14C lost by maturity was in abscised tissue.

The proportions of 14C assimilated at the four stages of development and recovered in seeds at maturity were quite similar to comparable proportions of assimilated 14C recovered in the seeds of maize (Zea mays L.) grown nearby.

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