Science and practice have proven that grapes are amongst the most precious and valuable dietary products for the human body. In order to preserve the high quality and valuable composition of the grapes, various processing methods and a diverse range of varieties are applied. The quality of grape juices is influenced both by production protocols and the characteristics of the raw material grapes. The study focuses on the monitoring during the growth period of the influence of photosynthesis in the accumulation of nutrients in grapes, mainly the content of phenolic compounds, ensuring the optimal harvest time according to the content of sugars and the concentration of total titratable acidity. The results of phytomonitoring, with the help of Phytomonitor PTM-48A of vines under lysimeter conditions, and the results of the chemical composition of the obtained grape juice are presented.