Enzymic assay of 10−7 to 10−14 moles of sucrose in plant tissues

Procedures are described for measuring sucrose in plant extracts or freeze-dried tissue in the range between 10−7 and 10−14 moles. The method is based on the destruction of pre-existing glucose and fructose, followed by the hydrolysis of sucrose and reduction of NADP+ by a series of coupled enzymic reactions. Depending on the sensitivity required, the NADPH is determined directly with a spectrophotometer or a fluorometer, or is amplified as much as 30,000 times before fluorometric assay. The procedures suggested for the macro level are simpler than current methods, and those suggested for microanalysis are several orders of magnitude more sensitive. With this technique, single palisade parenchyma cells and single spongy parenchyma cells of Vicia faba leaflets were each found to contain about 2.2 pmoles of sucrose