The important condition of the environmental improvement is mobilization and wide introduction of introduced trees and shrubs, which have already had successful preliminary investigation in the botanical gardens and dendrological parks and have shown characteristics of high ornamentality. The snowberries are such perspective but not so widespread plants now, which have very high decorativeness and attractiveness during almost the whole vegetative period, which is especially important when creating urban landscape compositions. Observations on the development of snowberries in the street landscapes ofKievhave shown quite high resistance of plants to the megapolis conditions, which made us to conduct the study of their functional state in the places with the most intensive traffic. The purpose of the study was to determine the functional state and photosynthetic potential of plants of the genus snowberry ( Symphoricarpos Duhamel) different species in the megapolis conditions. Seasonal inductive changes of chlorophyll fluorescence parameters of leaves of 9 species of the genus snowberry ( Symphoricarpos Duhamel): S. albus (L.) S.F.Blake, S. × chenaultii Rehder, S. × doorenbosii Krűssm., S. hesperius G.N.Jones, S. mollis Nutt., S. occidentalis Hook., S. orbiculatus Moench, S. oreophilus A.Gray, S. rivularis Suksd. are studied. For the assessment of the functional state of green plants a method based on the study of correlation of changes of intensity of chlorophyll fluorescence induction (CFI) with photosynthetic reactions in chloroplasts of leaves was used. To measure parameters of fluorescence and its inductive changes in the field conditions we used a portable device – a fluorometer Floratest (developed by the Engineering Center of V. M. Glushkov Institute of Cybernetics of National Academy of Sciences ofUkraine). The study of seasonal changes in the parameters of CFI of the leaves has revealed very small seasonal variability of the parameters of CFI in the leaves of snowberries: on average, the intensity of fluorescence at the maximum F p 1 and F p 2 decreased by 4,0 and 1,5 %, and the coefficient К 1 by 3,4 %, indicating on the high stability of electron transport processes near the reaction centers of photosystem II (FSII). The analysis of normalized inductive changes of fluorescence intensity in the time range of the slow decline of fluorescence showed slight decrease in the intensity of dark photochemical processes: К 2 ( Rfd ) ratio decreased only by 6,0 %. Thus, by means of the comprehensive analysis of functional indicators we found the high stability of photosynthetic processes in snowberry leaves, which allow the plants to maintain their ornamental features for the long periods of time. The analysis of the content of metal pollutants in the different parts of common snowberry plants ( S. albus ) was carried out using an atomic absorption spectroscopy method. Preparation of the bioprobes was carried out by such method as ozonation in a muffle furnace, followed by extraction in nitric acid. Determination of the content of metals in the prepared filtrates was carried out with the use of flame atomization (in the case of determination of large quantities) on the «C115-M1» spectrophotometer and electrothermal atomization (in the case of determination of trace quantities) on the «Saturn-3» spectrophotometer with the complex «Graphite-2». The comparative analysis of the accumulation of metal pollutants and the parameters of CFI of S. albus leaves in the park zone and near the transport line at Sevastopolska square has established the negative influence of the complex of factors on the activity of reaction centers and the effectiveness of dark photochemical processes. So, according to the «coefficient of plateau» K pL , which controls the number of inactive reactive centers of FSII, their growth is determined by 50–60%. Also, within the limits of 30–50%, the reduction of the Rfd parameter is registered, indicating a decrease in the activity of dark photochemical processes, that is the Calvin cycle. At the same time, the effectiveness of the light phase of photosynthesis in the leaves of S. albus on the experimental plots of Sevastopolska square in relation to similar indices obtained for plants of the park zone of the Institute of Horticulture of the National Academy of Sciences of Ukraine, does not change significantly, within 4,0–6,5%. The latest information obtained indicates that there is significant stability of the light phase of photosynthesis in the relation to the dark photochemical processes in snowberry plants and their high adaptive potential in the conditions of the urban environment. The results of the research allow us to recommend previously tested in Kyiv city conditions introduced snowberry species for the further usage in the plantations in the megacity conditions, and in particular in the places with the high level of contamination.
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May 24, 2018
Huanxi Zhao 
Open Access
