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Crop Science Abstract -

Water Stress Effects on CO2 Assimilation, Photosynthate Partitioning, Stomatal Resistance, and Nodule Activity in Soybean1


This article in CS

  1. Vol. 20 No. 4, p. 431-434
    Received: Sept 12, 1979

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  1. Gary A. Finn and
  2. William A. Brun2



14CO2 assimilation, photosynthate distribution, stomatal resistance, and acetylene reduction activity of vegetative soybean plants [Glycine max (L.) Merr., var. ‘Clay’] were examined 3 hours after pulse labeling the leaves with 14CO2. The plants had previously been water stressed for 20 hours by polyethylene glycol additions to the culture solution. Photosynthetic CO2 exchange rate (CER) and acytelene reduction activity of control and water stressed soybean plants were also monitored for 6 hours following polyethylene glycol induced water stress.

14CO2 assimilation and specific nodule activity (SNA) decreased and stomatal resistance (r8) increased with increasing water stress in the 14CO2 labeling experiment. There was a significant negative correlation (r=−0.71) between SNA and r8• Dry weights of leaves, of stems plus petioles, and of nodules were significantly decreased in the water stress treatments, while root dry weights increased. Water stress resulted in a redistribution of 14C with a greater proportion of the 14C being translocated to the roots and nodules at the expense of the leaves.

In the time course study, CER decreased after the imposition of an abrupt water stress (−12 bar), but total nodule activity was not affected. It is suggested that in. hibition of nodule activity under long term water stress was not caused solely by the decreased CER, but also by changes in photosynthate pool sizes.

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