Anatomical, Morphological, and Biochemical Characteristics of Different-Aged Needles of Pinus sibirica Du Tour (Middle Urals)

The aim of the present study was to investigate the anatomical, morphological, and biochemical characteristics of Pinus sibirica Du Tour needles of different ages, growing in their natural habitat in the taiga zone (Middle Urals). Anatomical and morphological parameters of the needles were analyzed in cross-sections using the «SIAMS MesoPlant» image processing system. The content of lowmolecular antioxidants, such as proline, ascorbic acid, phenolic compounds, including flavonoids, and the level of lipid peroxidation (LPO) in the needles were analyzed using standard spectrophotometric methods. It was shown that with the needle aging a decrease in anatomical and morphological parameters such as cross-sectional area, mesophyll area, and central cylinder was observed. The thickness of the covering tissues (epidermis and hypodermis) did not change significantly with the needle aging. It was found the decrease of green pigments concentration in needles due to a significant reduction in chlorophyll a, as well as a decrease in the ratio of chlorophyll a to antenna pigments with the needle aging. The content of carotenoids and chlorophyll b in the needles did not change significantly, indicating the stability of antenna pigments pool. A significant increase in lipid peroxidation was observed in 4-year-old needles, as a result, th antioxidant defense system was activated, manifested by an increase in the phenolic compounds and free proline content. The accumulation of ascorbic acid decreased with the needle aging.