The determination of the seasonal changes of juglone and total phenolic contents in walnut leaves

In this study, seasonal changes from May to October in juglone (5-Hydroxy-1,4-naphthoquinon) and total phenolic contents of the leaves of native cultural varieties (Şebin, Yalova 2, Yalova 3, Yalova 4, 1974/7) of walnut (Juglans regia L.) were investigated. Further, relations between juglone-phenolic content, juglone-climatic factors and phenolic content-climatic factors were established by applying correlation and regression tests. After isolation from walnut leaves, juglone and total phenolic contents were determined by spectrophotometric methods. The study was carried out in both 2006 and 2007 years. On the basis of means of the two years, although some differences are existed depending on the varieties, generally both juglone and phenolic contents were found at top level from middle of August to middle of September and the lowest level were seen in May. On the other hand, statistically significant positive correlation between juglone and phenolic contents of the leaves was found (r: 0,893 ; P<0,01). While there was no significant correlation between juglone and climatic factors, there was significant negative correlation between phenolic content and wind rate has been found in Yalova 2 variety (r:-0,692 ; P<0,05). In the case of differences among varieties, maximum mean juglone content was determined in Yalova 2 (3,51 mg/g leaf) and minimum in Yalova 4 (2,26 mg/g leaf). Maximum phenolic content was determined in Yalova 2 variety as has been in juglone case, and minimum phenolic level was seen in 1974/7 variety (49,3 mg/g leaf).Keywords: Climatic factors, correlation, juglone, phenolic content, regression, seasonal changes, walnut.