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Soluble Carbohydrates in Development Sorghum Caryopses¹

Soluble components of sorghum [Sorghum bicolor (L.) Moench] caryopses of field-grown plants taken from anthesis to 45 days postanthesis were assayed with gas-liquld chromatography and correlated with caryopsis fresh weight, dry weight, and maturity. Levels of the three primary sugars present, sucrose, fructose and glucose, were maximum (µg/caryopsis) at 12 to 15 days; inositol and raffinose were maximum at 18 to 21 and 27 to 33 days, respectively. Sucrose concentrations decreased to a constant level at day 24 and remained constant through day 45. During the first 15 days, glucose and fructose levels were similar;, thereafter, fructose levels were lower than glucose and only low fructose levels were detected in the caryopsis by day 39. Three major time intervals can be described by the data in the development and metabolism of the caryopsis: I, 8 to 18 days; II, 21 to 30 days; and III, 33 to 45 days. Rate of fill, water content, and sugar concentrations reached a maximum during Interval I. The rapid decrease of sucrose with the subsequent attainment of constant levels, the attainment of maximum caryopsis fresh weight, and the beginning of black layer formation were observed during Interval II. Maximum dry weight (physiological maturity), minimum rate of water loss and increased molar concentrations of sucrose were observed during Interval III. Day 33 was determined as the precise time of physiological maturity. Total sugars comprised about 5% of the caryopsis dry weight at day 15 and 0.8% on day 42.

Key Words: Gas-liquid chromatography • Physiological Maturity • Sorghum bicolor

² Associate Professor, Dep. of Plant Sciences; graduate student, Dep. of Soil and Crop Sciences; associate professor, Dep. of Soil and Crop Sciences; respectively, Texas A&M Univ., College Station, Tex.

Received for publication February 8, 1981.