Abstract
The genus Rumex is classified as an invasive parasitic plant in agriculture. Although other types of Rumex are widely used in herbal medicine due to their antimicrobial, antioxidant, antitumor and anti-inflammatory effects, there is practically no information about the potential of Rumex confertus Rumex tianschanicus Losinsk. and Rumex thyrsiflorus Fingerh for the treatment of various diseases. A study of the reaction of the photosynthetic apparatus of immature plants of three sorrel species (Rumex confertus, Rumex tianschanicus Losinsk. and Rumex thyrsiflorus Fingerh.) the sudden effect of low positive temperatures for 72 hours. The stimulating effect of cold on many parameters characterizing the photosynthetic activity of sorrel was noted. A different reaction of the photosynthetic apparatus of the studied species was revealed. This experiment's results indicate a relationship between the state of nutrients in the soil and competition between species. Phytochemical analysis made it possible to detect anthraquinones, flavonoids, tannins, phenols, phenol- and amino acids in the studied Rumex species. It has been shown that cold stress can have both stimulating and inhibitory effects on the synthesis of biologically active substances of plants. The Rumex confertus species showed the greatest resistance to cold stress. Keywords: Rumex, photosynthesis, cold stress, physiological state.