A comparative evaluation of the fluctuating asymmetry of the leaf blade Betula pendula Roth for different methods of plant material fixation

The influence of plant material fixation methods on the index of fluctuating asymmetry of Betula pendula Roth leaves is determined. The methods used were herbarization under pressure and leaves fixation in a solution of ethyl alcohol (45%). Biological material was collected in natural phytocenoses of the Pritalskaya zone of the Middle Urals and in technogenically formed territories, including soil contamination with heavy metals. The FA level of Betula pendula Roth leaf blades obtained on freshly harvested material increases in the gradient of toxic load and reflects a natural increase in soil contamination with heavy metals (Zn, Cu, Pb, Cd, etc.). The smallest deviation from the actual FA values obtained on freshly harvested material is given by a method of herbarization of leaves. The correlation coefficients are 0,94–0,99. Plant material fixation in an alcohol solution leads to more than 10-fold deviation of FA values from the real ones. The correlation between the studied morphological parameters of fresh and alcoholic leaf blades is 0,17–0,70. The signs «distance between the bases of the first and second veins of the second order from the base of the leaf» and «angle between the main vein and the second vein of the second order from the base of the leaf» are more distorted. Correction coefficients are proposed that allow to level out the differences in the FA level between the results obtained on freshly collected material and recorded by different methods. For the herbarization method, regardless of where the plant material is collected, the correction factor to be entered for the FA values of the fixed leaf blades is (–) 0,0004. For the method of leaves fixation in an alcohol solution, the coefficient value is (–) 0,00075 for material collected in undisturbed communities, and (+) 0,0045 for technogenically disturbed communities.