Nº 4 (2025)

Structural and functional parameters of juvenile plantsHeracleum mantegazzianum Sommier & Levier were studied in laboratory conditions. The plant illumination intensity was modeled based on observations of the light regime in the ground layer of natural populations of the species. Growing H. mantegazzianum under illumination of 250 μmol/m²s PAR(simulating the spring period) showed that at the initial stage of juvenile growth, the contribution of the main phytomass to the leaves and a high rate of net photosynthesis maintained a relative growth rate of 80 mg/g·dry weight day. The plants adapted to a decrease in illumination to 20 μmol/m²s PAR (simulating the summer period) by lengthening the petioles, decreasing the leaf density, and increasing the size of the light-harvesting complex of leaf pigments. Limitation of light resources caused a decrease in the relative growth rate to 14 mg/g dry weight day. Restoring the illumination level to 250 μmol/m²s PAR (simulating the autumn period) activated growth and contributed to the storage of plastic substances, mainly in the underground organs of plants. The structural and functional changes in juvenile H. mantegazzianum revealed in the experiment indicate high efficiency of light resource use in spring and autumn, as well as a significant decrease in metabolic activity during summer shading. This strategy promotes effective growth during a long growing season and the preservation of the number of juvenileH. mantegazzianum under conditions of intraspecific competition.

The spatiotemporal variation in the wing length of pied flycatchers breeding near the Middle Ural copper smelter (MUCS) and in the background area were analyzed in 1996–2023, a period of significant reduction in industrial emissions. Females and males were on average smaller near MUCS than in the background area probably due to the forcing the low-quality individuals into suboptimal (polluted) habitats. Yearlings had shorter wings than older birds. WL of males increased with increasing melanization of the upper body. Mean WL and proportion of old individuals among breeding birds increased over the study period. The body size of partners in breeding pairs did not correlate. The larger breeding birds, the earlier they started egglaying and the more eggs and fledglings produced.