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Seasonal and Fertility-Related Changes in Cottonseed Protein Quantity and Quality¹

Utilization of seed protein from cotton (Gossypium hirsutum L.) as an ingredient of food products for nonruminant animals may provide producers with a salable seed commodity in addition to oil and meal. It was therefore important to establish the effects that environmental conditions migbt have on cottonseed protein quantity and quality (amino acid composition).

Cotton was grown at two levels of N fertility at each of two locations in Mississippi. At each location, N concentration was higher in cottonseed produced in high-N N plots than in seed produced in low-N plots. For the single harvest at Starkville, enhancement of seed N by fertilization was 1.18%. For the first five harvests at Stoneville, enhancement of seed N ranged from 0.85 to 1.10%. A stratified harvest at Stoneville enabled the identification of seasonal influences on seed size and chemical composition. Both seed size and seed N concentration decreased with later developmental periods. Seed oil concentration, however, increased with later developmental periods.

Both N fertility and seasonal patterns caused slight, but statistically significant, changes in the amino acid composition of cottonseed protein. Generally, as seed N increased, the concentrations of lysine, threonine, glycine, and alanine in the seed protein decreased; concentrations of arginine and glutamic acid increased. Because both N fertilization and seasonal factors can influence cottonseed protein quantity and amino acid composition, comparisons of these factors should be made only among environmentally similar samples.

Key Words: Gossypium hirsutum L. • Seed development • Amino acid composition • Storage protein

² Plant physiologists, ARS, USDA, P.O. Box 225, Stoneville, MS 38776, and plant physiologist, ARS, USDA, P.O. Box 5367, Mississippi State, MS 39762.

Received for publication May 31, 1977.