Adaptation of Juvenile Heracleum mantegazzianum Sommier & Levier Plants to the Light Regime under Laboratory Conditions
摘要
The structural and functional parameters of juvenile plants Heracleum mantegazzianum Sommier & Levier plants were studied under laboratory conditions. The illumination intensity of plants was modeled based on observations of the light regime in the ground layer of natural populations of the species. Growing H. mantegazzianum at an illumination of 250 µmol/(m2 s) PAR (spring period modeling) showed that during the initial stage of juvenile growth, the contribution of the main phytomass to the leaves and the high rate of net photosynthesis supported a relative growth rate of 80 mg/g dry mass day. The plants adapted to decreased illumination to 20 µmol/(m2 s) PAR (summer period modeling) by lengthening petioles, reducing 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 mass day). Restoring light levels to 250 µmol/(m2 s) PAR (autumn period modeling) activated growth and contributed to the storage of plastic substances, mainly in the underground organs of plants. Structural and functional changes in H. mantegazzianum juveniles that were revealed during the experiment indicate the high efficiency of light resource use in spring and autumn, as well as a significant reduction in metabolic activity during summer shading. This strategy promotes efficient growth during the long growing season and maintenance of the number of H. mantegazzianum juvenile plants under conditions of intraspecific competition.