PHOTOSYNTHETIC ACTIVITY OF АCTINIDIA DELICIOSA LEAVES IN CONDITIONS OF PROLONGED DROUGHT IN THE SUBTROPICAL ZONE OF SOUTHERN RUSSIA

The results of studies of photosynthetic chlorophylls a, b and carotenoids of Actinidia delicata leaves in the subtropical zone of Russia are shown. A. deliciosa (kiwi) is grown in the humid subtropics of the Krasnodar Territory at the Adler Experimental Station, a branch of the Russian Institute of Plant Growing. The cultivation area is 5.5 hectares; the plant placement is 5 × 4 m. The soil is low-humus alluvial meadow. The purpose of the work is to study the physiological and biochemical parameters characterizing the crop's resistance to environmental stress factors in order to identify the most adapted kiwi cultivars to the conditions of the subtropical zone of the Krasnodar Territory. Studies on the content of photosynthetic pigments in kiwi leaves were conducted in 2023–2024 at the Laboratory of Plant Physiology and Biochemistry of FRC SSC of RAS (Sochi). The objects of study were 9 kiwi cultivars: ‘Abbott’, ‘Allison’ – early ripening; ‘Monty’, ‘Monty S’, ‘Bruno’ – medium; ‘Tomuri’, ‘Matua’ – mid-late; ‘Hayward’ (‘Hayward’), ‘Hayward Russian’ (‘Hayward Russian’) – late. In 2023, the dry matter content ranged from 24.72 to 36.86 % in early summer, and by the end of summer, against the background of rising air temperatures, it reached 40.05–47.40 % for ‘Bruno’, ‘Abbott’, ‘Tomuri’, ‘Hayward’ and ‘Allison’ cultivars. High rates were set in 2024 from July to August – from 29.51 % (‘Hayward’) to 40.75 % (‘Tomuri’), in October – 43.20–53.80 % for ‘Matua’ and ‘Bruno’, respectively. Maximum carotenoid content in 2023 from 0.35 mg/g (‘Bruno’) to 0.41 mg/g (‘Hayward Russian’, ‘Tomuri’), and in 2024 0.33–0.36 mg/g (Abbott, Bruno). The minimum is for Matua and Monti cultivars (0.24–0.29 mg/g). It was revealed that with the violation of the hydrothermal regime in the humid subtropics, the ratio of chlorophylls to carotenoids increased to 4.44–6.98 units, which confirms the kiwi's resistance to changes in external environmental factors.