Seed embryonic death in invasive populations of Ulmus pumila L. and Ulmus suberosa Moench in the steppe Dnieper region

Aim. Analysis of seed embryonic death and seed viability as a indexes of the genetic and reproductive state of Ulmus pumila L. and U. suberosa Moench to determine the mechanisms of invasiveness of their populations in the Dnieper steppe. Methods. Morphological, anatomical, cytological, statistical. Results. Investigated U. pumila populations differed on indexis of the embryonic death, seed viability and seed productivity. Populations growing in more favorable environmental conditions are distinguished by a better reproductive, physiological, and genetic conditions. Two from three U. pumila populations are characterized by low rates of embryonic death, high viability indices and seed productivity. This can indicate their heterogeneous origin and a significant level of heterozygosity. Vice versa, U. suberosa population has a high rates of embryonic death of seeds and low seed viability which may be due to population's limited and/or its poor physiological state and a decrease in heterozygosity. Conclusions. There are different levels of heterozygosity in the U. pumila population at the steppe Dnieper. Probably seed reproduction and distribution of this species is not significantly limited by genetic, physiological or environmental factors. Populations of U. suberosa in this region are characterized by worse genetic status. Seed reproduction of invasive populations of this species can be significantly limited. Keywords: seed embryonic death, empty samara, seed viability, heterozygosity, invasive populations, Ulmus pumila L., Ulmus suberosa Moench.