Evaluation of the functional state of peach varieties (Prunus persica Mill.) when exposed hydrothermal stress to plants

The article presents data on the change in the ratio of pigments and fluorescence of chlorophyll in peach leaves in the optimal period of vegetation and under hydrothermal stress. When determining the resistance of a peach to unfavorable environmental factors, methods based on laboratory, fixed changes in the physiological and biochemical processes occurring in plants are used. In the period of inadequate water availability, the water deficit in peach leaves increased to an average of 15%, while less stable - an increase in the parameter to 18% was observed. It is shown that the xeromorphic character of the leaf apparatus is associated with a slight change in the anatomical characteristics of the leaf (the thickness of the leaf blade before and after the drought), which determines the permanence of the turgor. In this case, in the leaves of resistant varieties, the loss of turgor is insignificant (LSD (p ≤0.05) = 7.24); the thickness of the leaf fluctuates within 0.20 mm. On the background of stress impact, a clear varietal difference was shown, which allowed us to develop a scale for a comparative assessment of the resistance of peach varieties and clones. During the active growth of the assimilation surface, an increase in the amount of green pigments in the leaves of experimental plants was noted. Perspective varieties of peach contain significantly higher amounts of chlorophylls compared to other varieties (LSD (p ≤0.05) = 0.30). Under unfavorable conditions, in these varieties the ratio of the sum of chlorophylls to carotenoids is higher, which is confirmed by their more developed adaptive potential. Reorganization of the pigmentary apparatus during the period of hydrothermal stress is accompanied by an increase in the coefficient of photosynthetic activity (Kf_n) and a decrease in the fluorescence level (F_T) of chlorophyll. Thus, the water deficit, pigment composition and fluorescence of chlorophyll make it possible to identify the resistance of peach varieties and clones to the action of hydrothermal stressors. Based on the results of the studies, the most resistant varieties and clones of peaches have been identified for the humid subtropics of Russia (Larisa, Early bloy, Medin red, Slavutich, Donetskij zheltij, Vanity and Form 1).