The metabolic characteristics of small-leaved linden (Tilia cordata Mill.) adaptation under urbanized environment conditions

Abstract

The increase of anthropogenic pollution in urboecosystem leads to degradation of woody vegetation that adversely affects the functioning of the protective green space. The impact of anthropogenic loading is shown by change of a series of physiological and biochemical processes and the formation of adaptive mechanisms in plants. The ability of plants to respond appropriately to external stimuli is a necessary condition of their existence and adaptation to environmental conditions. Metabolic reorganization in plant cells that occur in response to exogenous pollutants plays a major role in determining their resistance to adverse factors. As the body adapts within genetically inherited norms reactions, its ability to withstand fluctuations in environmental factors is determined by individual ecological potency. One of the most sensitive species to anthropogenic pollution is small-leaved linden (Tilia cordata Mill.), which is widely presented in dendroflora of Ukraine cities. Analysis of the species metabolic characteristics in terms of urbanized environment and the assessment of the prospects of identified changes using in practice bioindication research is the goal of this work. One of the central components of plant metabolism is protein metabolism. In terms of all local ecotypes of the studied urboecosystem a statistically significant change in the content of total nitrogen and protein in small-leaved linden leaf plates to control was observed. Reducing the concentration of total nitrogen and protein in species leaves is in accordance with the degree of urbotechnogenic pressure enhancement in the next different-functional landscape city zones: the area of the integrated landscaping → the area of the house-building complex → the area of transport routes → the area of industrial complexes. Carbohydrate metabolism in plants under stressful conditions changes towards accumulation of soluble sugars, which takes place in local ecotypes of Ivano-Frankivsk urboecosystem. The content of the above-mentioned substances in lime leaves increases from 4.6 % in the area of ​​integrated landscaping to 23.8 % in the area of ​​industrial complexes, compared to the background territory. The content of mineral elements in Tilia cordata leaves within the city ranges from 119 mg/g in the area of the integrated landscaping up to 159 mg/g in the area of industrial complexes, respectively, 1.5– 2 times higher than the figure on the background area. Fall of starch concentration in the small-leaved leaves is in accordance with the level of anthropogenic impact intensification in the local city ecotypes, ranging from 1.2 times in the area of ​​integrated landscaping to 1.6 times in the area of industrial complexes. Reducing the polysaccharide amount in plant’s assimilation organs is caused by inhibition of photosynthesis and the activity of enzymes that control its metabolism. In terms of urboecosystem the close correlation relationships were set between the vast majority of the analyzed organic and mineral components of small-leaved linden leaves. The presence of water-soluble carbohydrates in leaves significantly correlated directly proportional with the content of mineral elements and inversely proportional to the number of nitrogenous compounds and polysaccharides. Accumulation of ash by lime leaves adversely affects the synthesis of proteins, starch and cellulose accumulation and stimulates the formation of lipids, which clearly reflects environmental urbotechnogenic pressure and formation of defensive reactions in plants. Nitrogenous compounds are formed in close direct connection with polysaccharides and at the same time have an inverse correlation with the parameters of the fat-like substances content in the species leaf plates. Positive dependence was found between the cellulose and starch content in assimilative organs, accurate feedback was established between the synthesis of starch and lipids. Fat-like compounds metabolism is associated by weak positive relationship with the content of water soluble carbohydrates in leaves, but is not correlated with cellulose tissues content. Given the informative content of the main parameters of mineral and organic components of Tilia cordata leaves and species sensitivity to anthropogenic pollution, it is rational to use it as bioindicator in assessing the ecological condition of urbanized territories.