The effect of the altitudinal gradient on the morpho-anatomical structure of one-year-old Norway spruce needles
Norway spruce is one of the most important species from ecological, ornamental, and economic-production point of view. The paper deals with the variability of morphological and anatomical traits of one-year-old spruce needles sampled from three different altitudinal zones in the Prijepolje region, Western Serbia. The analyzed morphological characteristics included needle length and width, while the anatomical elements investigated were needle thickness, resin ducts diameter, epidermis and cuticle thickness, hypodermis height, vascular bundle width, as well as the width of xylem, phloem, and endodermis. The results of the analysis of variance (ANOVA) found statistically significant differences (p˂0.05) both among sites and among trees within sites for almost all analyzed spruce needle characteristics. The observed variation in the dimensions of protective structures (epidermis and cuticle thickness, hypodermis height, resin ducts diameter, and endodermis width) and conductive structures (xylem, phloem, and vascular bundle width) along the altitudinal gradient indicates the adaptive characteristics of Norway spruce and its ability to adapt to different site conditions.