Glucose and potassium levels were determined from cotton bolls at early stages of development by a glucose reagent strip method and a potassium ion selective electrode. Over 90 developing bolls from five genotypes at three growth stages (10, 18 and 25 days-post-anthesis [DPA]) were collected in replicates from fields in Stoneville, MS, in August 1993. Locules were removed, extracted with water, and assayed for soluble glucose and potassium. Glucose levels among varieties were significant when computed as mg/g fresh locule weight, but not as mg/boll. Measured levels of glucose were ~30, 10, and 5 mg/g for 10, 18, and 25 DPA, respectively. Glucose levels (mg/g) among varieties were significant at 10 DPA and highly significant at 25 DPA, but not at 18 DPA. Results showed that the strip method can precisely determine the glucose level in cotton bolls at different stages of development. The technique can also show different levels of glucose among different varieties.

The potassium levels of the same samples determined by ion selective electrodes seemed to increase from 10 DPA to 25 DPA. Typical levels were 4, 3.5, and 6 mg/g fresh locule weight for 10, 18, and 25 DPA cotton bolls, respectively. Among varieties, significant differences were observed when potassium levels were computed as mg/boll (except 25 DPA) and mg/g fresh locule weight (except 10 DPA). There were no significant differences among varieties for all growth stages when expressed as mg/g fiber weight. One genotype showed a higher level of potassium at both developmental stages than the other varieties. Therefore, the glucose strip and potassium selective electrode methods are effective techniques in determining glucose and potassium levels for developing cotton bolls.

Acknowledgements

The contribution of D. Dixon is gratefully appreciated.