Determination of Starch in Plant Tissues

Abstract

IntroductionDuring a study of the carbohydrate distribution in grape canes, it became necessary to have a method for the estimation of small amounts of starch. A fairly rapid, accurate method yielding easily reproducible results was desired in order that the analysis of a great number of samples could be completed in a short time.An excellent survey of the literature dealing with analytical methods for starch is given by ANTOLTON (11). Of all the methods listed, one described by THOMAS (9) for estimating starch in apple spurs seemed most suitable. The fundamental idea of THOMAS'S method is the direct determination of the combined reducing power of glucose and maltose produced by the action of diastase on starch under prescribed conditions. This method avoids the destruction of sugars which always takes place if complete hydrolysis with acids is attempted or if acid hydrolysis after diastatic conversion of the starch is used according to the Official Methods (6). This fact was shown by THOMAS and confirmed in the present work. THOMAS determined the reducing sugars by means of the calorimetric method of BENEDICT and OSTER-BERG (1), which involved the reduction of a picrate-picric acid solution to picramic acid. When this method was tested out on pure starch it always yielded high results (table I). The use of mercuric nitrate as a clarifying agent was also unsatisfactory since it yielded a precipitate which was slow in settling and difficult to filter. Moreover, mercuric nitrate exerts an oxidizing influence on sugar solutions (5). It is evident that the clarifying agent must be chosen to suit the particular type of substrate obtained from the different plants.The procedure which was found most satisfactory is as follows:

Agronomic and physiological characteristics of a rice leaf early senescence mutant during its whole growth period

“…In the process of NSC extraction, the original sugar extract was analyzed for determining the concentrations of soluble sugars as described by Somogyi (1945), whereas the residue was dried at 75 °C for starch extraction and analysis by the method of Shriner. (1932).…”