Peculiarities of adaptive responses in Betula pendula Roth, growing in the waste dump of the Kedrovsky coal mine

The majority of publications are devoted to the study of adaptive reactions in Betula pendula under technogenic pollution of the urban environment, but there are few works on structural and functional parameters on poor substrates, including dumps. The aim of the research was to reveal the peculiarities of B. pendula adaptive reactions in the waste dump of the Kedrovsky coal mine. The object of research was Betula pendula, which grows in various ecological conditions on the territory of the waste dump of the Kedrovsky coal mine, which is located 25 km to the north of Kemerovo (56°32'52''N, 86°05'54''E). The age of the trees was 25-30 years; bonitet class II with density 0.3-0.5. We conducted the experiment in 2013-2016 at two observation sites (OS): 1 - control - a site situated 5 km from the waste dump with a phytocenosis similar in composition; 2 - experiment - a planned waste dump with a formed phytocenosis of natural origin. According to agrochemical properties, embryozems of all OS were characterized by a high content of exchange potassium (100...240 mg/kg) and low content of mobile phosphorus (10...50 mg/kg). In embryozems of OS 1, in comparison with OS 2, we revealed a low content of nitrate nitrogen (3.6.6.0 mg/kg).The analysis of the content of mobile forms of heavy metals (Pb, Cd, Cu, Zn, Mn, Ni, Co, Fe, Cr) did not show an excess of the existing MPC. We collected the material during the growing season (June-August). For the study, we sampled leaves from ten model trees of a satisfactory vital state (from 10 branches of the lower third along the crown perimeter) in each study area. We selected birch leaves with a completely unfolded leaf plate without visible signs of damage from 9 to 10 h by means of a pole pruner. We studied water relationship indicators according to a generally accepted methodology. The daily loss was calculated as the difference in the weight of the leaves at the beginning of the experiment and in the weight of the sample in a day in percent, the water retention capacity as the difference between the water cut and the daily losses. We determined the ascorbic acid content by the titrimetric method using 2.6-dichlorophenolindophenol sodium; phenolic compounds-by the Leventhal-Neubauer method; the content of free proline - by the method of Bates with co-authors in Voskresenskaya's modification using an acidic ninhydrin reagent; sugars - by the methods of Filiptsova and Smolich. A cumulative analysis of the characteristics of the water regime and biochemical indicators in the birch demonstrates mutual conditioning of these parameters. In the course of the experiment, we revealed some peculiarities of B. pendula adaptive reactions, including changes in water relationships of trees, in the direction of increasing water retention capacity (up to 56.5%) and a decrease in daily losses (up to 19.8%) (See Fig. 1). On the planned dump in the test samples, the sugar content exceeded the control by an average of 9%, and the proline amino acid-by 41% (See Fig. 2). In the leaves of B. pendula, the content of phenolic compounds increased throughout the whole period of observations. The greatest differences in this indicator were registered in July and exceeded control values by 14%. In June, the studied plants showed a maximum decrease (by 30%) in ascorbic acid, compared to control. The smallest range of variation in the investigated plants was detected by the content of phenolic compounds (17-19%) and water retention capacity (11%) (See Fig. 3). The revealed changes in the mechanisms of water homeostasis and the functioning of the antioxidant system of B. pendula allow us to consider them as adaptive and protective reactions aimed at its survival in the waste dump. The investigated indicators can be used in bioindication and for assessing the condition of woody plants in technogenically disturbed territories. The article contains 3 Figures, 29 References.

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