Seasonal character of the pigment content in the needles of Northern white-cedar in the conditions of the Nizhny Novgorod region

The seasonal character of the pigment content in the needles of decorative forms and varieties of Northern white-cedar (Thuja occidentalis L.) in the conditions of the Nizhny Novgorod region was studied. The relevance of the work is due to the urgent need to optimize the assortment of types of trees and shrubs used in the creation of urban plantings capable of performing sanitary- hygienic, decorative-aesthetic and recreational-balneological functions. The objects of the study were 9 ornamental varieties of Western thuja and its typical form of seed origin, related to exotics in the Russian Federation and the Nizhny Novgorod Volga region. They had the following nomenclature: Thuja occidentalis f. Rheingold; Thuja occidentalis f. Mr. Bowing Boll; Thuja occidentalis f. Woodwardii; Thuja occidentalis Tiny Tim; Thuja occidentalis f. Golden Smaragd; Thuja occidentalis f. Mirjam; Thuja occidentalis f. Golden Globe; Thuja occidentalis f. Danica; Thuja occidentalis f. Sunkist. The mother plants were of the same age and were located within the boundaries of a single experimental site – the arboretum of the Nizhny Novgorod State Agricultural Academy. Its territory, according to the system of forest-growing zoning, is included in the zone of coniferous-broadleaf forests and is assigned to the area of coniferous-broadleaf (mixed) forests of the European part of the Russian Federation. The content and balance of plastid pigments were detected by spectrophotometric method: SF-2000 spectrophotometer with GRASS GIS 7.6.1 / QGIS 3.4 software. Contrast differences in the pigment composition of the needles of the studied varieties of Northern white-cedar are dynamic in the initial and final phase of the growing season. In autumn, they contained significantly more chlorophyll-a in the tissue cells of annual needles (2.28 ± 0.042 mg/g) than in spring (1.29 ± 0.056 mg/g). The average generalized for the growing season was 1.78 ± 0.046 mg/g. The presence of chlorophyll-b during the observation period is unstable: autumn estimates (0.62 ± 0.039 mg/g) are higher than those obtained at the beginning of the growing season (0.62 ± 0.031 mg/g), with a generalized average of 0.62 ± 0.025 mg/g. The sensitivity of different indicators of pigment composition to changes in weather conditions during the growing season varies. While maintaining general trends in the seasonal dynamics of the parameters of the pigment composition of needles, representatives of different forms and varieties of Northern white-cedar have a sufficiently pronounced specificity in this regard and demonstrate the significance of inter-variety differences throughout the year.