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This article in CS

  1. Vol. 19 No. 1, p. 54-58
    Received: May 1, 1978

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Genotypic Differences for Reduction in Carbon Exchange Rates as Associated with Assimilate Accumulation in Soybean Leaves1

  1. W. D. Hanson and
  2. R. Y. Yeh2



Six soybean [Glycine max (L.) Merrill] genotypes which differed in growth characteristics were selected to test the hypothesis that genotypes differed in their capacity to maintain carbon exchange rates (CER) at original levels as assimilate accumulated. Chilling (4 C) a 3 cm section of the leaf petiole for 3 hours created a 5.3-fold increase for sucrose and 1.4-fold increase for starch in the leaf relative to the control leaves with nonchilled petioles. Levels of sucrose and starch continued to increase with an additional 4 hours of chilling the petiole. Sucrose and starch levels increased in the leaf blade primarily as compared with the petiole and leaf veins. Transpiration rates and stomatal diffusive resistances were similar for chilled and nonchilled petiole treatments. All genotypes had similar decreases in stomatal diffusive resistances during 3 hours of chilled petiole treatment. Differences in reduction of carbon exchange rates (CER) were found among genotypes when petioles were chilled for 3 hours. Those genotypes whose CER were unaltered by chilling did not accumulate more sucrose and starch in the leaves than genotypes whose CER declined. In a 7-hour chilled petiole study, the change in CER was inversely proportional to level of sucrose in the leaf blade. Genotypic differences for maintaining CER with assimilate accumulation in the leaf were not found.

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