Accumulation of polyphenols at the beginning of photomorphogenesis in vitro tea plant cultures under the influence of different light intensity

Introduction. An important direction in the biotechnology of plant cell cultures is the search for factors and influences that contribute to increasing the accumulation of pharmacologically valuable metabolites in them, including polyphenols. These factors include light, the effect of which activates the processes of photomorphogenesis in in vitro cultures, regulates their differentiation and metabolic processes. All this depends on the intensity of the light flux, the origin of the cells and tissues cultivated in vitro, as well as the economic value of the synthesized plant metabolites. One of the promising pharmacologically valuable crops are tea plants (Camellia sinensis L.), as well as callus cultures initiated from them, which are characterized by the accumulation of various polyphenols, including flavans – substances with P-vitamin capillary-strengthening activity.

The aim of the study was to compare the effect of different light intensity on the morpho-physiological characteristics of tea callus cultures, as well as the accumulation and localization of polyphenols in them.

Material and methods. The object of the study was tea callus cultures of stem origin grown for 40 days at light intensity: 50 µmol·m^-2·s^-1, 75 µmol·m^-2·s^-1 and 100 µmol·m^-2·s^-1 (low, medium and high intensity, respectively). Morphophysiological parameters of calluses (color, density, water content), the total phenolics and flavans content in them, as well as their localization were analyzed.

Results. The cultivation of tea calluses in the light was accompanied by their changing-over to photomorphogenesis, which manifested itself in the greening of the cultures and the chloroplasts formation in cells. The greatest efficiency of this process was noted at the high light intensity, which correlated with the maximum accumulation of polyphenols and flavans, exceeding that in cultures grown at lower light flux values. Consequently, the cultivation of tea callus cultures at different light intensities makes it possible to regulate the polyphenols accumulation in them – biologically active plant metabolites with antioxidant activity.