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The results of field and laboratory studies of drought tolerance in some Ficus carica cultivars of various origins are presented. It has been found out that under the conditions of the Southern Coast of the Crimea, the cultivar Sabrutsiya Rozovaya is characterized by high drought tolerance. Low resistance to dehydration was noted in the cultivars Vladimirska Krupna, Pomoriyskiy 6, Franziana Biella. It was revealed that in August, a decrease in water holding capacity occurs in all the studied cultivars. Using Chlorophyll Fluorescence Induction (CFI) method, an integrated assessment of the photosynthetic apparatus in the leaves of Ficus carica cultivars under conditions of simulated wilting is given. It has been demonstrated that drought is the cause of decrease in the photosynthesis light phase efficiency, the part of chlorophyll involved in the transfer of energy from light harvesting antenna complexes to reaction centers and the enhancement of non-photochemical photo quenching. A resumption of photosynthetic activity was observed with the normalization of leaf water supply in the resistant cultivar Sabrutsiya Rozovaya and the medium-resistant cultivar Iyulskiy. In the cultivars characterized with low drought tolerance, Vladimirska Krupna, Pomoriyskiy 6 and Ranniy iz Sozopol, the resumption of the water content in leaves was followed by a decrease in the variable fluorescence and photochemical activity of PS 2, which indicates further stress development in these cultivars and high sensitivity of their photosynthetic apparatus to dehydration. During the fruit ripening, on the background of water holding capacity decrease, water deficit in leaf tissues within 20-25% results in irreversible disturbances in the photosynthetic apparatus activity in Ficus carica cultivars that is proved by a decrease in the viability index below the vitality norm and may adversely affect the preparation of plants for transition to a state of rest.

There were conducted the studies of the water regime of the leaves of 6 apricot cultivars of various origin in connection with the ability to adapt to moisture deficit during the periods of the greatest summer drought manifestation on the Southern Coast of the Crimea. The genotypes with the highest adaptive potential under conditions of hydrothermal stress were identified (possessing the best water-holding characteristics combined with a high degree of repair after critical dehydration) - 'Nagycorosi Orias', 'Kazachok', 'Professor Smykov'. 'Hurmai' cultivar demonstrates labile resistance. 'Crimskiy Amur' and 'Alupkinskiy' display instability of water regime indicators as well as a relatively low ability to tolerate extremely high temperatures and lack of moisture.

Studies results of drought resistance degree of 4 Ficus carica varieties and 4 Prunus armeniaca varieties are presented. It was established that genotypes of ‘Sary Stambulskiy’ and ‘Sabrucia Rozovaya’ (F. carica), ‘Kazachok’ and ‘Professor Smykov’ (P. armeniaca) are characterized by a high level of adaptation to inadequate water supply. Their leaves show an increased ability to retain moisture in the wilting process and the ability to carry out the fullest possible tissue reparation after critical water loss. The relationship between peroxidase and polyphenol oxidase activity, as well as the concentration of proline with the implementation of protective mechanisms against the negative influence of dehydration was revealed. Characteristics of primary photosynthesis processes in water stress conditions were given. It was found that in F. carica varieties, the rapid fluorescence phase parameters are the most sensitive to dehydration. In P. armeniaca varieties, water stress causes an increase in basic fluorescence and decrease in variable.

The paper presents researches on biochemical assessment of grape cultivars of various origin. Grape cultivars, grown in the forest-steppe of Altai region, are characterized by the following biochemical composition of berries: sugars -10.7-17.8 %, acids -0.6-1.9 %, SAI -7.9-23.9. The cultivars and selected forms of Amur group exceeded the American one in their sugar content by 1.8 %, in acids -by 0.1 %. In Vitis amurensis Rupr. Group, a high sugar content was observed in the selective form 39 (15.1 %), in the group Vitis labrusca L. -cultivar 'Latviisky rozovy' (12.7 %). very early ripening cultivars 'Russky ranny' and 'Zhemchug bely' depended on weather conditions less than other cultivars since their variability in all indicators was insignificant or average. There was selected a cultivar 'Russky ranny' with consistently high sugar (16.1 %) content and low acid content (0.7 %).