Yana Fabriciusa, Sochi, 354002 Russia, e-mail MalukovaLS@mail.ru Received July 19, 2016 A b s t r a c t In the conditions of Russian Black Sea coast and in many other regions of the world (China, India) tea plant is faced with seasonal water shortages leading to a significant loss of productivity — according to different authors, up to 40-50 % (M. Mukhopadhyay et al., 2014; L.S. Malyukova, 2014). <...> In this regard, physiological and biochemical mechanisms of tea plant resistance to water shortages as well as the effectiveness of various exogenous inducers are being researched; more drought-resistant cultivars are being searched for the breeding. <...> The papers showed calcium effect on reducing oxidative damage in various plants (including tea plant) at drought by inducing antioxidant system (X.Y. Gao et al., 1999; M. Lee et al, 2004; S.S. Medvedev, 2005; H. Upadhyaya et al., 2012; E.G. Rikhvanov et al., 2014). <...> Calcium was introduced into the soil in the form of a natural fertilizer (clay and lime matter containing 40 % of CaO) at 100 kg CaO per ha along with macronutrients (N240P70K90) against solely N240P70K90 in control. <...> During summer periods of high moisture deficit (late July to August) we studied the dynamics of catalase activity in mature leaves and 3-leaf fleshes, pH of the cell sap, water supply and water loss, as well as chemical composition of plants and soil. <...> It was found that under the influence of calcium in the stressful period there were an increase in catalase activity in mature leaves (by 10-19 ml of O2/g within 3 min at different periods), a reduction of water loss (on average by 20 %), a lesser alkalescency of the cell sap (by 0.05-0.07 units), and a significant (by 27-33 %) increase in plant productivity, which indicates more stable functional state both during water stress and rehydration. <...> Catalase activity in shoots (to a lesser extent in mature leaves) correlated with the pH of the cell sap (r = 0.93 and r = 0.53, respectively), which determined its important role in the formation of tea plant oxidative state. <...> More adapted restructuring of the plants to extreme conditions and their subsequent effective recovery <...>