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This article in CS

  1. Vol. 22 No. 2, p. 381-385
    Received: Jan 12, 1981

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Carbohydrates in Sorghum Culms as Influenced by Cultivars, Spacing, and Maturity over a Diurnal Period1

  1. George G. McBee and
  2. F. R. Miller2



With increased interest in use of sorghum [Sorghum bicolor (L.) Moench] biomass for energy, additional information is needed on the influences of cultivars, maturity, spacing, and diurnal effect on levels of carbohydrates within the plant.

‘Combine Kafir-60’ (CK-60) and ‘Rio’ were grown in rows 100 cm apart with plant spacings of both 10 and 40 cm. Plants were harvested at preboot and early anthesis over a diurnal cycle of six different times. Upper and lower culm sections were analyzed for glucose, sucrose and starch.

Percentages of total nonstructural carbohydrates (TNC) were somewhat similar in both cultivars at preboot, reaching a maximum level of 18.3%. By anthesis, TNC peaked at 40.2% in Rio compared to 26% for CK-60, with the most dramatic increase occurring in the sucrose fraction.

Closer spaced plants (10 cm) tended to higher in TNC and during anthesis, upper culm sections of CK-60 and Rio contained 7.0 and 12.8% more TNC, respectively, than those spaced 40 cm apart.

Diurnal influences were more evident at the preboot stage with TNC peaking near 1630 in the afternoon and then declining. No significant diurnal trends could be detected for carbohydrates at anthesis.

Glucose decreased at anthesis in the upper culm section of the 10 cm plants as much as 24 and 46 mg/g oven dry weight (ODW) while sucrose peaked at 206 and 318 mg/g ODW for CK-60 and Rio, respectively. Starch increased significantly in all cultivar culm sections at anthesis for the 10 cm spacing and in the lower but was variable in the upper culm section of plants spaced 40 cm apart.

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