ABSTRACT
Flower abscission in upland cotton (Gossypium hirsutum L.) can affect yield and earliness of the crop. Although some physiological causes of abscission bave been investigated, little is known about the role of ovary carbohydrates in abscission. The objective of this study was to determine whether the concentration of carbohydrates in abscission. The objective of this study was to determine whether the concentration of carbohydrates in excised ovaries was related to subsequent abscission. In 1989, eight cotton genotypes (DPL 50, DPL 90, DES 119, MS 7803, MD 65-11 Normal leaf, MD 65-11 Sub Okra, and MD 65-11 Super Okra) were growing the field using conventional cultural practices. Open flowers on mainstem nodes 8 to 12 at position 1, 2, and 3 were either tagged and left undisturbed for abscission determination of harvested and frozen at -80 C. After freeze-drying, the ovaries were excised and ground dry with mortar and pestle. Glucose and starch concentrations were determined on ground ovary tissue. Averaged across genotypes, flower abscission was greatest at position 3 (94%) followed by position 2 (53%) and position 1 (25%). Glucose concentration was lower in position 3 ovaries (38 g kg-1) than in those from position 1 (47 g kg-1) or 2 (42 g kg-1). Genotypic differences in abscission were detected only at position 2. One genotype, MD 65-11 Super Okra abscised 92% of its position 2 flowers. All concentration was less than 40 g kg-1 in MD 65-11 Super Okra and greater than 40 g kg-1 for six other genotypes whose flowers abscised less frequently. Ovary starch concentration was lower for MD 65-11 Super Okra (73 g kg-1) than for the other seven genotypes abscission by position were considered, the results indicated that low ovary glucose concentration and high increase chances of abscission. Genotypic differences were found in the concentrations of soluble sugars and starch. However, concentrations of carbohydrates in position 2 ovaries were not significantly correlated to abscission percentage.
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