Abstract. Scientific novelty and practical significance. Due to the presence of a strong root system, the grapes are a rather drought-resistant crop, but the lack of soil and air moisture adversely affects the growth and development of the plant, which ultimately significantly reduces the yield. In the soil and climatic conditions of the Astrakhan region, characterized by a high degree of aridity, as well as the presence of light chestnut structureless soils that retain moisture poorly, the study of the drought tolerance of grape varieties is particularly relevant. The purpose of the research was to study the degree of drought tolerance of grape varieties to identify the adaptive mechanisms of plants in the arid conditions of the region. To achieve the goal, the following tasks were solved: determination of the total water content in the leaves and the relative turghorescence of the leaves; determination of water deficiency in the leaves; determination of water-holding capacity of leaves, as the main indicator of drought resistance. Methods. The object of research was 12 grape varieties of various technological orientations grown on the territory of the vineyard of the Caspian Agrarian Federal Scientific Center of the Russian Academy of Sciences. Were investigated early ripe varieties (Vostorg, Astrahanskij skorospelyj, Madlen muskatnyj, Koroleva vinogradnikov, Shasla belaya, Bianka, Fioletovyj rannij) and mid-season varieties (Kishmish Luchistyj, Husajne rozovyj, Levokumskij). For control were taken: Kodryanka – for early ripe varieties; Karamol – for varieties of medium ripening. The experience laid down by the method of B.A. Dospehov. The scheme of planting bushes 1250.0 pcs/ha. Formation of bushes – fan, four-sleeve. Irrigation was carried out on furrows with a norm of 600.0–800.0 m3/ha. To assess the adaptive resistance of grape varieties to drought, we determined: the total water content in the leaves, the relative turborescence of the leaves according to the Witherly method, the water deficit in the leaves according to the Litvinov method, and the water retention capacity according to the Eremeev method. Results. The lowest water deficit in the group of early ripening varieties was found in the varieties Kodryanka, Madlen muskatnyj and Koroleva vinogradnikov (4.9–5.7 %); in the group of middle-ripening varieties, the varieties are Levokumskij and Kishmish Luchistyj (4.7–5.0 %). As a result of the research, 7 varieties with a high degree of drought resistance were identified: Kodryanka, Astrahanskij skorospelyj, Koroleva vinogradnikov, Shasla belaya, Karamol, Kishmish Luchistyj and Husajne rozovyj.
Simple Modification of Karl-Fischer Titration Method for Determination of Water Content in Colored Samples