This chapter concerns the assessment of environmental and varietal affects on photosynthetic pigment groups. It is revealed that the dynamics of pigment accumulation in subtropical plants within the conditions of Russia’s damp subtropics is a complex process and depends on species plants. With this in mind, hazelnut maximum green pigments were achieved in May, and then in August, there was a decline associated with the onset of short periods of drought and increased temperatures. In Actinidia and tea plants, the highest content of green pigments is achieved in August, which is associated with the biology of these crops. However, regardless of species, with the onset of the dry period (July–August), plants increase their accumulation of carotenoids. The high content of carotenoids that accounts for stress during a period of water availability is evidence of their participation in the formation mechanism of subtropical plants’ resistance to adverse conditions.

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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).

The article presents the results of studies on the dynamics, qualitative and quantitative composition of phenolic compounds of tea raw materials and tea of new forms of selection of the Institute. The regularity in their synthesis by months is determined, which affects the quality indicators of the end product and necessitates blending to the repaired tea. The accumulation of tannins in tea raw materials depends on hydrothermal conditions, in particular, the amount of precipitation. The content of tannin increases from May to June, then there is some decline in their content, due to hydrothermal stress, slowing the synthesis of tannins in the tea leaf. The content of the water-soluble fraction gradually increases from May to July, and then there is a slight decline. It is shown that the accumulation of phenolic compounds in tea raw materials varies during the collection season. The contents of theaflavins increased from the beginning of the collecting sheet to its completion. The content of thearubigins showed peaks: the lowest rate in June, the highest in August. It was revealed that a sharp drop in the synthesis of thearubigins in June is associated with the onset of the summer dormancy of growth and synthetic processes. The synthesis of both indicators depends on meteorological conditions. The comparative analysis of the samples of tea raw materials collected from experimental plants is carried out. It is shown that the content of tannin and extractive substances in the raw materials of the studied varieties and mutant forms is high. In terms of the ratio of theaflavins and thearubigins, tea made from experienced raw materials meets international requirements. Determination of the qualitative composition of the catechin group of green tea, produced from raw materials of new forms, showed a high level of accumulation of the main groups of catechins.