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Seasonal changes in the total water content in walnut leaves
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Having in mind importance and dependence of physiologic functions upon water, the investigations of its dynamics in the leaves of walnut trees cv. were carried out. The following standard cultivars of walnut trees, belonging to the collection plantation located in the surroundings of the town of Zaječar (Eastern Serbia). Toward the end of each month of the vegetation period, the leaves were sampled and the total content of water was determined by drying samples at 105 oC to its constant weight. The study shows the average results of the total water content in leaves per years of investigation (1999-2003). The results point to a high dependency of the total water content in leaves on available precipitations and air temperatures, which is proved by the coefficient of correlations (r=0.418; r=-0.494). The greatest total water content in leaves was, on the average, at the beginning of the vegetation and ranged from 77.3% (in April) to 70.51% (in May), while it was the lowest in the second part of the vegetation, amounting to 61.8% (in August and September), and 59.6% (in October). Averagely for all cultivars, the total water content was 66.2%. Depending on all conditions, the greatest total water content was in 1999 (67.5%), while the lowest one was in the year of 2002 (63.6%). The greatest average content of total water was found in the leaves of the cv. Šampion (68.4%), and the lowest in the cv. Elit (65.0%).