Variability of morphological and anatomical characteristics of Serbian spruce (Picea omorika /Panc./ Purkyne) needles of natural population located in the Milesevka river canyon

Serbian spruce (Picea omorika /Panc./ Purkyne) is rare and endangered tertiary relict and endemic species in the Balkan Peninsula. Its natural distribution is fragmented and restricted to western Serbia and eastern Bosnia and Herzegovina, mainly in the canyon of middle course of the Drina river. Since the mid-19th century, the number and size of populations have been steadily decreasing accompanied by a decline in the number of mature individuals, endangering natural regeneration is endangered. The objective of this study is to determine variability within Serbian spruce (Picea omorika /Panc./ Purkyne) natural population in the canyon of the Milesevka river on the basis of morphological and anatomical characteristics of needles and, thus, to broaden knowledge on this rare and endangered species. Twigs with needles collected from all mature individuals that represent the population were used as material for the study. The following morphological and anatomical characteristics were measured: NL- needle length; NH - needle height; NW - needle width; CT+EH - cuticle + epidermis height; HH - hypodermis height; VB - vascular bundle diameter; No of SC - number of resin channels; SC diameter - resin channel diameter. The average values of the measured characteristics are: needle length 13.23 mm; needle width 1239.93 ?m; needle height 608.63 ?m; cuticle + epidermis height 11.49; hypodermis height 17.59 ?m; vascular bundle diameter 220.64 ?m; number of resin channels 0.74; resin channel diameter 52.36 ?m. The characteristics with the highest variability are as follows: number of resin channels (161.64%); resin channel diameter (25.35%); hypodermis height (20.79%), while the needle width is a characteristic with the lowest variability (6.39%). The results of the analysis of variance showed very high statistical differences within population for all studied characteristics (p<0.01; ?=0.05). In order to make the results clearer, it is necessary to investigate the genetic diversity and population structure by analyzing various phenotypic characteristics in specially designed experiments (e.g. progeny tests) as well as by analyzing appropriate DNA markers. The studied population must be involved in continuous conservation and breeding processes, especially through appropriate forms of ex situ conservation.