In connection to the climate changing and draught frequency increasing in the spring-summer period the fractional composition of water (combined and uncombined water) in leaves of apple from May to August 2011, 2012 were studies. Combined and uncombined waters have different functionality for the life of plants. An uncombined water in leaves determines intensity of physiologic processes while the combined is responsible for plants resistance to unfavorable conditions. The fractional composition of water was studied in apple leaves of varieties bred by All-Russian Research Institute for Fruit Crop Breeding of RAAS, Bolotovskoye, Irmus, Orlik, Orlovim, Orlovskoye Polosatoye, Sinap Orlovskiy, Yubiliar in comparision to widespread varieties – Antonovka, Melba and Welsi. The study established that the varieties examined were well-adapted to drought in May, at the beginning of summer, as well as at the end of August and in September. At the beginning of July and in June higher indices of drought resistance were registered for Orlovim and Yubiliar, with the highest indices of combined water content. The completion of shoots growth and development of leaves system in all apple varieties was associated with increase of combined water amount in the leaves in August. In September, the number of combined water remained higher that suggested high adaptivity of the varieties being studied. The highest content of combined water in autumn was registered for Sinap Orlovskiy, Antonovka, Boltovskoie, Irmus.

Assessment is made for heat-resistance of 10 promising domestic and foreign apple varieties, as well as for their drought- resistance (leaf tissue water content, water holding capacity and turgorescence); also, impact of weather conditions on implementation of its drought and heat resistance by the research subject is determined. The article highlights the best in Ukraine’s Forest-Steppe environment by the above economical and biological properties apple varieties.