Fruit and seed morpho-biology of some species of Sorbus (Rosaceae) introduced at Peter the Great Botanical Garden.
The study was focused on seed propagation of some Sorbus L. species, introduced at Peter the Great Botanical Garden of the Komarov Botanical Institute of Russian Academy of Sciences (the Garden BIN RAS), and their fruit and seed characteristics. The Garden BIN RAS holds collection of 119 Sorbus specimens ranging over 46 species and forms. Since the publication of the article of G.A. Firsov and N.P. Vasiljev  the collection has been supplemented by two taxa (S. aucuparia 'Alaya Krupnaya' and S. aucuparia 'Likyornaya'). The second generation from local seeds of 26 taxa has been obtained in 2011-2018, including 22 taxa for which the second generation has been obtained for the first time since the introduction to the Garden BIN RAS: S. aucuparia subsp. amurensis, S. aucuparia L. f. rosea, S. buschiana, S. cashmiriana, S. commixta, S. eburnea, S. esserteauiana, S. fedorovii, S. frutescens, S. graeca, S. intermedia, S. matsumurana, S. meinichii, S. minima, S. persica, S. reflexipetala, S. roopiana, S. rufo-ferruginea, S. torminalis, S. turkestanica, S. velutina, S. zahlbruckneri. The seed structure has been described, seed morphometric characteristics (weight, size, embryo to endosperm length ratio) and their germinative capacity has been determined. These characteristics can be used as additional taxonomic characters for distinguishing Sorbus species. The studied species can enrich the arboreal flora of Saint Petersburg parks and gardens and become valuable fruit trees for private gardens as well. The highest seed germination has been observed in S. persica, S. frutescens, S. meinichii, S. esserteauiana, S. matsumurana, so these species can be recommended for propagation by seeds.