Variation in chemical compounds of walnut (Juglans regia L.) leaves with tree age

Abstract

In this present study, we investigated the chemical compounds in the fresh leaves of ancient walnuttrees (Juglans regia L.) aged 25, 75, 100, and over 400 year. Under similar environmental conditions,the fresh leaves of walnut trees were collected and analysed for chlorophyll molecules as chlorophylla, chlorophyll b and carotenoids, enzymatic compounds (ascorbate peroxidase (APX), catalase (CAT)and superoxide dismutase (SOD) activities) and non-enzymatic compounds (proline, total solubleprotein, total phenolic compounds), flavonoid and reducing sugars (glucose, sucrose, total solublesugar). In addition, the oxidative stress level was determined by measuring lipid peroxidation (MDAmalondialdehyde)and hydrogen peroxide (H2O2). Significant differences in the chemical compositionof the fresh leaves were found between the 4 different tree age classes. In general, the results showedthat mean chlorophyll pigments were increased with increasing the age. There was also a generaltrend that mean glucose and starch concentrations increased with the age, while mean sucroseconcentration decreased, but no changes were noted for mean total soluble carbohydrate. On theother hand, mean SOD concentration decreased with increasing the age. Other chemical compounds(mean proline, total soluble protein, malondialdehyde, hydrogen peroxide, APX and CAT), however,did not show clear trends with the age. As a result, these pioneer study have provided valuable insightinto the variation in the chemical constituents of walnut tree leaves in relation to the age, and it canbe used to better understanding, managing and fighting against pathogens of walnut ecosystems infuture studies.