Abstract
The present study is aimed at comparing the nitrogen concentration in leaves among populations of Lythrumsalicaria, correlating the nitrogen concentration data with the type of soil cover, the state and size of rivers, the intensity of agriculture, fragments of the riverbed. Despite the abundance of data on plant nitrogen, plants differ in species composition at each site, grow in certain climatic and soil conditions and are subjected to special human pressure. Due to genetic and phenetic differences, different sampling methods, nitrogen determination methods and individual estimates, the data obtained on the amounts of nitrogen in certain species is not easy to transfer from one region to another. Exceeding critical loads for eutrophication was detected in various parts of Lithuania [1] and then tested in this country and turned out to be higher than in other Baltic countries. For our study, only leaf blades were used, and nitrogen concentrations were determined by the Kjeldahl method. Significantly significantly higher (p <0.05) nitrogen concentrations in leaves were found in L. salicaria populations growing near small rivers (3.4%), compared with large ones (2.8%). Other selected parameters of the river and its environment in most cases did not significantly affect the nitrogen concentration in the leaves of Lythrumsalicaria populations. Further experimental study of the data on the saturation of L. salicaria with nitrogen is necessary.