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  1. Vol. 20 No. 1, p. 86-90
     
    Received: May 10, 1979
    Published: Jan, 1980


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doi:10.2135/cropsci1980.0011183X002000010020x

The Effect of Carbohydrate Concentration on the Respiration Rate of Soybean1

  1. B. M. Coggeshall and
  2. H. F. Hodges2

Abstract

Abstract

Two experiments were conducted to determine the relationship between respiration rate and carbohydrate concentration in source and sink tissue in soybean (Glycine max (L.) Merrill). Experiment I was conducted during VS/R1, R2, and R4 stages of maturity. Defoliation, 92% shading, and control treatments established a range in sugar and starch concentrations for source leaves and the corresponding above.ground sinks at each stage. This range was primarily due to a reduction in source size by defoliation, or a reduction in photosynthate source by shading, thereby reducing the carbohydrate supply to the sinks. This range was primarily due to a reduction in source size by defoliation, or a reduction in photosynthate source by shading, thereby reducing the carbohydrate supply to the sinks. Respiration was positively correlated with carbohydrate content in V8/RI and R2 tissues in which growth respiration predominates. However, where maintenance respiration likely predominated (R-4 leaves and pods) the respiration-carbohydrate content correlations were poor.

Experiment II was conducted during the R5 stage of maturity. Control, 92% shading, defoliation, and depodding treatments resulted in a range in sugar and/or starch concentrations in source leaves and pod tissues. Defoliation and shading reduced the carbohydrate supply from the source to the sink as in Experiment I. The two-thirds depodding treatment was not severe enough to affect the carbohydrate concentration in the pods. However, starch accumulated in the leaves 7 days after the treatment was initiated. A significant positive relationship was found in the R5 leaves among respiration and sugar or starch concentrations. Conversely, an insignificant relationship was found in pods which contained predominately storage tissue undergoing maintenance respiration.

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