The ability to synthesize various secondary metabolites is a specific feature of higher plants. The most common secondary metabolites are phenolic compounds or polyphenols formed practically in all plant cells [1,2]. Increasing interest in these substances is due to their use as capillary-protecting, cholagogue, antitumor, and other drugs [3][4][5].Phenolic compounds differ considerably in composition and chemical activity. They include phenylpropanoids (hydroxycinnamic and hydroxybenzoic acids) and flavonoids (flavones, flavonols, anthocyans, etc.) that are present in the form of monomeric, oligomeric, and polymeric compounds in plants [1,2]. The number of known phenolic compounds (more than 9000) continuously increases [2].Phenolic compounds are produced practically in all plant cells. Accumulation of these compounds depends on the species and organ of plants and the phase of plant development. For example, woody plants synthesize a greater amount of phenolic compounds than herbaceous plants [6]. It should be emphasized that the intensity of metabolic processes is the highest in growing organs, particularly in leaves [2,7]. Phenolic compounds are strongly accumulated in both young and old tissues [1,2,8]. This type of distribution is related not only to biosynthesis, but also to catabolism of compounds [2,8].Considerable progress was made in studying the chemical composition and metabolism of phenolic compounds. However, the functions of these compounds in plants are poorly known. Previous studies have shown that several phenolic compounds are involved in the regulation of photosynthesis and respiration. They serve as components of electron transport chains in mitochondria and chloroplasts and uncouple oxidative phosphorylation [2]. Much recent attention was paid to salicylic acid, which acts as a signal molecule in plants [2,9]. Phenolic compounds protect plants from a variety of stress factors, including pathogens, UV irradiation, and heavy metals [10,11]. The protective effect of phenolic compounds is associated with their ability to prevent or decrease the severity of oxidative stress accompanying the influence of adverse factors [12]. It should be noted that the ability of plant cells to synthesize phenolic compounds indirectly reflects their resistance to stress [13]. Therefore, study of the ability of plant tissues to synthesize phenolic compounds is of considerable importance.Much attention is given to wheat as one of the most important cereal food crops cultivated in the five contiAbstract -The formation of soluble phenolic compounds, including flavonols, was studied in winter ( Erythrospermum , Lutescens 230, and spring cultivars (Lada) of wheat ( Triticum aestivum L.). The contents of soluble phenolic compounds and flavonols were 1.8-2.6 and 0.5-1.3 mg/g fresh weight, respectively. These results illustrate the similarity of phenol metabolism in leaves of winter and spring wheat cultivars. The exception was the cultivar R 47-28 that accumulated the maximum amount of phenolic compounds (e.g., flavono...
