Abstract
An automated enzymatic hydrolysis procedure was developed to analyze aqueous leaf extracts for soluble carbohydrates in the presence of chlorophyll. Following an initial estimate of free reducing substances in the extracts from individual soybean {Glycine max [L.] Merr. 'Braxton') leaflets, separate portions were incubated with invertase or amyloglucosidase. The increase in ferricyanide reduction after incubation with the enzyme was assumed to represent the concentration of sucrose or starch, respectively, in the original extract. Use of an autoanalyzer operating in a double-beam mode compensated for interference from chlorophyll and other endogenous pigments. Extraction efficiency was checked by successive boiling-water extractions, and enzymatic incubation conditions were verified by a series of internal calibration standards. After 3 successive boilingwater extractions of § min each, more than 95% of the soluble sucrose was removed from the leaflets. Although the conditions of these procedures were insufficient for quantitative removal of all soluble starch present in the soybean leaflet, they represent a compromise that yields an aqueous extract which is amenable to enzymatic assay while avoiding excessive degradation of labile carbohydrates during the extraction process. This method allowed for a rapid comparison between drought-stressed and non-stressed soybean leaflets, which were collected during field experiments and stored in a laboratory freezer for later analysis of osmotic potential and soluble carbohydrates, e.g., glucose, fructose, sucrose, and starch.
Influence of pump bandwidth on the efficiency of side-pumped, double-beam mode-controlled lasers: establishing a new record for Nd:YLiF_4 lasers using VBG
