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Variability of morpho-anatomical characteristics of the needles of Picea omorika from natural populations in Serbia

In the research on the variability of the morpho-anatomical properties of the Serbian spruce (Picea omorika /PanČ./ Purkyne), we investigated seven characteristics of 2-year-old needles, collected from four natural populations in Serbia. The hypodermis of the Serbian spruce subject to our study is single layered. The needles sport 0–2 resin ducts, predominantly of the external type (touching the epidermis). The average values were as follows: 13.60 mm (needle length), 1.49 mm (needle width), 0.82 mm (needle thickness), 22.83 μm (cuticle+epidermis thickness), 17.51 μm (hypodermis thickness), 0.74 (number of resin ducts), and 51.82 μm (resin duct diameter). Needle width and thickness were the most variable characteristics. Principle component analysis visualizes an overlapping among the populations in the region of Mt. Tara and a partial separation of the population from Mileševka Canyon. Cluster analysis suggests the biggest differentiation between geographically distant populations (Štula and Mileševka Canyon). All the analyzed characteristics were compared with appropriate literature sources.