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ŠUMARSKI LIST 3-4/2020 str. 34     <-- 34 -->        PDF

P. nigra are adapted to resist hydraulic forces and prolonged submersions (Šiler et al., 2015).
The geometric morphometric leaf shape analyses provide valuable information about variance components obtained through the asymmetric component (such as random deviations from the bilateral asymmetry in the heterogeneous environment) and heritability of the leaf shape (symmetric component) (Albarran-Lara et al., 2010; Viscosi and Fortini, 2011; Miljković et al., 2019). According to the results for both habitats the percentage of shape variability was higher for the symmetric component, which implies that the genetic factor has more contribution in the variability of the leaf shape. The large number of gene activities and auxin have determined leaf shape in environmental conditions in which leaf maturate (Drost et al., 2015).
In this study intraindividual variation was observed for the shape (statistically significant effect of leaves, Table 1). However, in other study the clonal variability (genetical variability) of petiole lenght and FALEAF index were observed, while for SLA there was no variability (Table 2) (Huber et al., 2008; Al Afas et al., 2005; Al Afas et al., 2007; Čortan and Tubić, 2017).
The observed results within the present research confirmed no significant differentiation between different habitats (flooding/not flooding) (Table 2) for specific leaf area, petiole lenght and FALEAF (Table 2). Even though population „E“ is differentiated the most, with highest values, there are no significant differences between populations in terms of SLA and petiole lenght, while mild significant differences were observed for the composite index FALEAF (0.031 vs. 0.029; flooding vs. nonflooded) (Table 2). It is obvious that analyzed leaf traits showed great tolerance to flooding compared to the not flooding areas within the research area. In other studies the specific leaf area (SLA) decreased less by flooding than leaf area (Bacanamwo and Purcell, 1999; Dias-Filho and Carvalho, 2000; Herrera et al., 2009), which indicates that decreased leaf expansion was not associated with carbohydrate accumulation in leaves (Bacanamwo and Purcell, 1999). The dry leaf mass was lower in the flooding area but not significantly statisticaly diffrent than in the non-flooding area (2.4 g vs. 2.6 g; respectively). The flooding causes significant decrease in leaf dry mass production (Dias-Filho, 2002; Caetano and Dias-Filho, 2008; de Oliveira and Joly 2010), and dramatically reduce leaf size and shape (Zhuang et al., 2011; Rood et al., 2003). The difference between and within species with regards to tolerance and response to flooding regime were confirmed. As flooded and drained conditions exerted different selection pressures on trait expression, the optimal values for constructive and