Seed production of Heracleum sibiricum (Apiaceae) in Moscow region

Background. Heracleum sibiricum forms three types of flowers: perfect, stami-nate, and pistillate. Four types of H. sibiricum individuals have been identified according to the degree of branching of the inflorescence (double umbels on shoots of I, I–II, I–III, and I–IV orders of branching), which correspond to three types of synflorescences: a single terminal double umbel, a raceme of double umbels, and a panicle of double umbels. Data on the seed set of H. sibiricum are fragmentary. The purpose of this research is to study the seed production of Heracleum sibiricum in the Moscow region, taking into account the de-gree of branching of its synflorescences. Materials and methods. Our studies were carried out in natural conditions of Moscow region from 2018 to 2021 according to generally ac-cepted methods of studying plant seed sets. Results. The seed production of double umbels consistently decreases with an increase in the order of the shoot on which they are formed. However, the number of ovules and seed production of terminal umbels is always higher than that ones of individual double umbels on shoots of the following orders. In individuals with different degrees of synflorescences branching, the seed production of double umbels on shoots of the same branching order naturally increases with increasing branching of the shoot system. The contribution of the seed production of double umbels to the total seed production of individuals with an increase in the degree of branching of the shoot system naturally changes. The proportion of seeds from terminal double umbels decreases, but number of seeds from double umbels on shoots of II and III orders gradually increases due to an increase in their number. Conclusions. Heracleum sibiricum is characterized by high number of ovules and seed set (up to 9800 seeds per individual) and the proportion of per-fect and pistillate flowers forming full seeds (96–98 %). These characteristics ensure its successful seed reproduction in natural conditions.