Primary metabolites in the leaves and fruits of three pear cultivars during the growing season

Abstract

Primary metabolites (sugars and organic acids) in leaves and fruits of the pear cultivars Conference, Concorde and Williams were investigated during the growing season in Slovenia. Leaves were sampled 15 times from Apr. 25 to Oct. 22. Fruits were sampled seven times from Jun. 14 to Aug. 23. The contents of sugars (glucose, fructose, sucrose, and sorbitol) and organic acids (malic, citric, shikimic, and fumaric) in leaves and fruit were determined by high performance liquid chromatography (HPLC). Similar dynamic patterns were found in the glucose, fructose, sucrose and sorbitol in leaves and fruits of the genetically related cultivars Conference and Concorde. Leaf sugar was low at the beginning of the growing season when the leaves were not completely developed. Generally when sucrose increased in leaves it decreased in fruits. At the end of June the total sugar content in leaves reached its peak then rapidly decreased. At the same time, total sugar in fruits increased. From the beginning of August, total sugars in fruits increased regardless of the sugar content in leaves and likely due to decomposition of starch. After harvest, the contents of individual sugars (glucose, fructose, sucrose, and sorbitol) in the leaves decreased until the beginning of October when, just prior to leaf drop, they increased in all cultivars. Key words: Pyrus communis, sugars, organic acids