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ŠUMARSKI LIST 5-6/2015 str. 33     <-- 33 -->        PDF

measures will neutralize losses and preserve the remaining gene pool, which is currently threatened by extinction.
Foregoing points to the need for variability research which have been exploring a number of black poplar (Populus nigra L.) leaf morphological parameters in four populations along Vojvodina area. Results of black poplar leaf morphologic variability have been shown in this paper.
Material and Methods
Materijal i metode
The examination of black poplar degree of leaf morphometric parameters variability within and between populations was performed on selected test trees in four populations at their natural habitat, in the area of Vojvodina (Figure 1). Populations are located in the basin of the major rivers in Vojvodina: two populations are located in the basin of Danube river (the upper course -population A and the lower course of Danube – population D), one is placed in the basin of the Tisa River – population B and the last one in the basin of the Sava River – population C (figure 1). These four sites have similar site characteristics; they are placed on flat ground right next to the riverside, which are under the periodical flooding (up to 65 days per year). The geological substrate consists of clayey sands with quartz and other silicate and it has sandy structure. The soil is alluvial on alluvial deposit, medium-deep (41–80 cm), loosely, fresh, skeletal (51–70% of the structure). Litter is medium represented, suggesting on favorable process of humification.
Within each of these studied populations 10 adult test trees were randomly selected. Leaves were randomly sampled from test trees during the growing season, when the leaves are fully developed (August-November). For the purpose of consistency, samples were collected from mature trees with approximately the same height (4–6 m) and the same part of the crown (outer part of crown, leaves of light, south side). In order to provide equivalent material required for comparison, samples were taken from the middle part of long shoot twig, because of the less pronounced polymorphism in relation to the leaves from basal and apical part of long shoot (Tucović 1965).
Analysis were carried out on a sample of 100 dried, healthy, undamaged leaves from each test tree, which is in total 4000 leaves from 40 test trees. On each leaf 9 morphometric parameters were analyzed, with a total of 36000 measurements. The measurements were performed with an accuracy of 1mm.
The analysis included the following morphometric parameters: a – length of leaf, b – width of leaf, c – petiole length, d – angle between the first vein and horizontal line, e – width of leaf at 1 cm from the top, f – distance between the base of leaf and the widest part of leaf, g – length of the whole leaf (leaf and stalk), h – number of veins on the left side of the leaf and i – number of veins on the right side of the leaf.
Obtained morphometric data were statistically analyzed using the software package Statistica 6.0. Results of measurements were statistically analyzed with descriptive statistic: mean value (x), minimum and maximum value​​ (min – max), variation range (R), standard deviation (SD), relative standard deviation (RSD). The one-way ANOVA was used to test differences between mean values of measured leaf parameters. Mean values were separated using Tukey’s HSD test, with significance levels of p<0,05 and p<0,01. The dendrogram of cluster analysis (Nearest Neighbor Method, Euclidean distance) was used to illustrate a hierarchical clustering of studied populations.
Results of descriptive statistics are represented in Table 1. The largest mean values of leaf length (a=93,43 mm), leaf width (b=73,39 mm), petiole length (c=54,71 mm), distance between the base of leaves and the widest part of the