Measuring glucose levels is a routine procedure in many physiological and agronomic studies, although it is expensive and time consuming. The objective of this study was to develop a rapid and inexpensive method of measuring glucose levels in cotton bolls. The procedure was based on a reagent strip commonly used for measuring blood glucose in diabetic patients, which made the strip technique very reliable. The strip and three other methods of measuring glucose (glucose hexokinase [HK], glucose oxidase, and anthrone method) were used to measure known concentrations of glucose standard solutions. Also, locules (lint and seed) from 15 days-post-anthesis cotton bolls were extracted with deionized water by shaking for 30 min. A strip was dipped in the extract for a minute, and the glucose level was determined the following minute using a reader/monitor. For comparison, glucose levels from the same extract were determined using the three other methods. In this experiment, glucose levels were ~1.5 mg/mL extract or 10 mg/g fresh locule weight for the 15 DPA cotton bolls. Results showed that the strip was strongly correlated to glucose HK (r=0.991**), glucose oxidase (r=0.998**), and anthrone method (r=0.996**). Therefore, the strip is comparable to the three methods. The strip (r=0.948**) also measured the concentration of the standard solution precisely, but not as precisely as glucose HK (0.998**) or glucose oxidase (r=0.999**). The precision and the accuracy of the strip seemed to decline as concentration increased (e.g., >300 mg/dL or 3 mg/mL). Thus, within the appropriate detection range of 0.1 - 3 mg/mL, the strip technique should be very useful for routine glucose determination in cotton boll development considering the time (2 minutes/sample), cost ($0.70/sample for materials), and portability.

Potassium concentrations in developing cotton bolls are also of interest. The water extracts used for the glucose test were further analyzed for soluble potassium using a standard pH meter equipped with an potassium ion selective electrode. The method consists of standardizing the meter, adding an ionic balance solution, and measuring the potassium levels in ppm after 20 min. equilibration. The potassium electrode is effective for monitoring approximately 4500 samples at a projected cost of $0.25/sample. Therefore, these methods should be useful in many physiological and genetic studies because of the simplicity, accuracy, speed of analysis, and low cost.