HISTOCHEMICAL OBSERVATION AND CELLULAR-DISTRIBUTION OF ASCORBIC-ACID IN PERSIMMON LEAVES

This study was carried out to resolve the discrepancy of data for the proportion of ascorbic acid and dehydroascorbic acid in persimmon leav es at the final stage of the season and to clarify their cellular dist ributions using histochemical and biochemical techniques. Fresh persim mon leaves were collected and used on July 31, September 5 and October 7, 1996. Ascorbic acid and dehydroascorbic acid in subcellular fracti ons were determined by the HPLC method that was found to be the most r eliable for separation. The percent of dehydroascorbic acid in the tot al leaves was found to be almost constant (between 32 and 37%) in all preparations tested. In all preparations, more than 90% of the ascorbi c acid and dehydroascorbic acid was found in the soluble fraction. The histochemical detection of ascorbic acid and an electron micrograph o f persimmon leaf cells showed that the reactive color, after the reduc tion of silver nitrate under acidic conditions, in the leaves of all t hree preparations was mainly found on the face side of columned-type p alisade parenchyma cells where chloroplasts were not rich and large va cuoles were seen. On the inner side of the palisade parenchyma cells w here chloroplasts were the richest, only weak color development was ob served. This study demonstrates that the percent of dehydroascorbic ac id in persimmon leaves did not exceed 40% at least until October 7. It also shows that in persimmon leaf cells, ascorbic acid is mainly loca lized in the cytosol of palisade parenchyma tissue cells where large v acuoles are seen.