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This article in CS

  1. Vol. 34 No. 2, p. 446-452
    Received: May 10, 1993

    * Corresponding author(s):
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Enzymatic Control of Nonstructural Carbohydrate Concentrations in Stems and Panicles of Sorghum

  1. Lee Tarpley,
  2. Sarah E. Lingle,
  3. Donald M. Vietor ,
  4. David L. Andrews and
  5. Frederick R. Miller
  1. D ep. of Soil and Crop Sci., Texas A&M Univ., College Station, TX 77843-2474
    C onservation & Production Systems, USDA-ARS, 2413 E. Highway 83, Welasco, TX 78596
    D ep. of Horticultural Sci., Texas A&M UNiv., College Station, TX 77843-2133



Sorghum [Sorghum bicolor (L.) Moench] stores starch as the principal nonstructural carbohydrate in grain, but primarily stores sucrose in stem. The extent of sucrose accumulation in stem varies among cultivars, and has been previously related to decline in activities of soluble sucrose-degrading enzymes in sweet sorghum stem. The hypothesis that soluble sucrose-degrading activity would vary inversely with patterns of sucrose accumulation was tested in panicles and stems of five diverse sorghum genotypes grown and sampled in the field from boot to post-black layer. Activities were greater in panicle than stem during inflorescence development, and invertase activities remained relatively greater in panicle during grain filling than in stem during sucrose accumulation. Panicle invertases were speculated to hydrolyze sucrose prior to endosperm import. In contrast, invertase and sucrose synthase activities were already low by the period of sucrose accumulation in stem regardless of the stem sucrose-accumulating abilities of the studied genotypes. A follow-up greenhouse study tested for parallel changes in levels of activity and mRNA for sucrose synthase, and provided evidence that activity was regulated by pretranslational control. In this study also, sucrose accumulated after sucrose synthase activity and mRNA levels were already low. A decline in soluble sucrose-degrading activities appears to be a prerequisite for, but cannot explain the extent of, accumulation of sucrose in stem.

Joint Contribution of the Texas Agric. Exp. Stn. (Paperno. TA 31319) and the USDA-ARS.

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Copyright © 1994. Crop Science Society of America, Inc.Copyright © 1994 by the Crop Science Society of America, Inc.