Accumulation of photosynthetic pigments and secondary metabolites in leaves of galega (Galega orientalis Lam.) cv. Gale depending on stand age and agrotechnologies during introduction in the middle taiga of Western Siberia

Plant biomass production and accumulation of bioactive substances are determined by a complex of physiological and biochemical mechanisms, environmental factors and agrotechnologies. The use of Galega orientalis as a forage crop throughout the world is largely due to its unique environmental adaptability and a large yield potential. Despite the widespread use of forage G. orientalis around the world, research data on photosynthetic pigments, vitamin C and flavonoids in green mass of the plants under a new environment are scarce, and for the north of Russia, it is completely absent. Earlier, we were the first to describe the phenological, eco-morphological features and photosynthetic potential, the productivity of green mass and seeds of G. orientalis for the zone of the Middle taiga of Western Siberia. This paper systematizes our first data on the accumulation of photosynthetic pigments, vitamin C, and flavonoids in G. orientalis plants at the site of introduction. The study aimed to characterize the content of these compounds during adaptation to new environment, depending on cropping practices and the age of the herbage. Introductory studies were carried out on the cv. Gale (an experimental plot, the village of Barsovo, Khanty-Mansi Autonomous Okrug - Yugra, Surgut district, 61°15′00″ N, 73°25′00″ E. 2013-2015). Plants were grown using peas as a cover crop, in monoculture with pre-sowing treatment of seeds with the Baikal-EM1 microbiological preparation (OOO NPO EM-Center, Russia), and in monoculture without treatment. The effects of the cropping practices on the total chlorophylls (Chl a + Chl b) in the leaves appeared in the 2nd year plants. Upon seed pre-sowing treatment with the Baikal-EM1 preparation, in the 2nd and 3rd year plants, the level of total chlorophylls by plant development phases was 19-22 % and 16-18 % higher than in the control). In mixed sowing total chlorophylls decreased at the end of the 2nd year but exceeded the control (by 33 %) by the end of the 3rd year. In the control, the Chl a level in the leaves of the 1st, 2nd and 3rd year plants averaged 1.23±0.10, 1.29±0.12 and 1.32±0.14 mg/g dry weight over the growing season. Over the 2nd year of growth, the content of Chl a in the leaves increased by 15 % on average upon the Baikal-EM1 application compared to the control and remained within the control values (1.20±0.23 mg/g) (р £ 0.05) in the mixed stands with pea plants. For the microbiological preparation, the average Chl a/Chl b ratio significantly (p £ 0.05) decreased over 3 years, which may indicate an increase in the adaptive potential of plants, and for the mixed crops, it remained within the control values. The proportion of chlorophylls (Chl a + Chl b) localized in the light-harvesting complexes (LHC) varied from 20 to 90 % depending on the plant phenophase, stand age, and the agrotechnology. In the control and two treatments, the correlation coefficients between Chl a/Chl b and the proportion of chlorophylls (Chl a + Chl b) localized in the LHC were r = -0.83, r = -0.93, and r = -0.65, respectively. Treatments did not lead to a statistically significant change in the Chl/Car index. Nevertheless, after inoculation with the Baikal-EM1 biological and in mixed sowing with peas, the accumulation of carotenoids exceeded the control. For all treatments over the years, the accumulation of all pigments in the leaves directly correlated with the hydrothermal coefficient (HTC). The content of Chl b and carotenoids turned out to be weaker associated with the temperature regime, while the first parameter directly correlated with precipitation during the season, and a negative correlation occurred for the second parameter. When inoculated with Baikal-EM1, the leaf level of vitamin C in the 1st and 2nd year plants increased compared to the control and was almost equal to the control in the 3rd year plants. In the 3rd year mixed sowing, the vitamin C content decreased compared to control. After application of the microbiological preparation and in the control, the content of flavonoids in the 3rd year plants switched to generative development sharply decreased, while in the sowing with the cover crop, where the virginal stage continued, it sharply increased (1.6 times compared to previous years). In general, our findings indicate that the biological Baikal-EM1 largely contributed to the adaptation of the 2nd and 3rd year plants of G. orientalis cv. Gale to a new environment.