Adaptation of Juvenile Plants Sommier & Levier to Light Regime in Laboratory Conditions

Structural and functional parameters of juvenile plants 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 under illumination of 250 µmol/ms 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/ms 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/ms 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 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 juvenile under conditions of intraspecific competition.