Format: ORAL

Sophia V. Yudina1,2, Ba Vuong Truong4, Nikolay A. Vislobokov1,3, Dmitry F. Lyskov1,3, Maxim S. Nuraliev1,3, Margarita V. Remizowa1, Alexander Kocyan5

1 M.V. Lomonosov Moscow State University, Moscow, Russia 2 The Institute for Information Transmission Problems RAS, Moscow, Russia 3 Joint Russian-Vietnamese Tropical Scientific and Technological Center, Hanoi, Vietnam 4 Department of Biological Resources, Institute of Tropical Biology, Vietnam Academy of Science and Technology, Ho Chi Minh City, Vietnam 5 Department of Plant and Microbial Biology, Botanical Museum, University of Zurich, Zurich, Switzerland

Burmannia is the largest genus of the pantropical family Burmanniaceae (Dioscoreales). Species of Burmannia demonstrate, on the one hand, actinomorphic bisexual flowers with typical monocot trimerous groundplan and, on the other hand, highly elaborated morphology that includes prominent floral tube with large longitudinal wings. We provide comprehensive analysis of inflorescence structure, floral anatomy and floral development for eight species of Burmannia with different life strategies (autotrophy, full mycoheterotrophy, partial mycoheterotrophy). In Burmannia, the basic inflorescence type is a thyrsoid of two cincinni, which is transformed into a botryoid in the few-flowered species via the reduction of lateral cymes to single flowers. The floral tube in Burmannia consists of a hypanthium and a perianth tube. In B. oblonga, inner tepals are seemingly absent from mature flowers. However, during early developmental stages of the flower these organs are present; but, their growth is arrested almost immediately after initiation. The gynoecium of Burmannia consists of synascidiate, symplicate and asymplicate zones. The symplicate zone is secondarily trilocular. The border between synascidiate and symplicate zones (i.e. the cross zone) is hard to recognize due to the absence of visible traces of postgenital fusion in the basal part of the symplicate zone. Species of Burmannia uniformly possess supralocular septal nectaries, i.e. located in the upper region of the ovary just below the ovary roof. Finally, species of Burmannia reveal a remarkable diversity of stamen-style interactions. The stamens are either tightly appressed to the style remaining free from it, or postgenitally fused with the style by their connectives forming a gynostegium. A gynostegium is otherwise only found in some lineages of Apocynaceae of eudicots that have similar complex synorganised flowers. The work was supported by the Russian Science Foundation (project 21-74-10006) and by IITP RAS FFNU-2022-0037.