Vol 108, No 9 (2023)

The structure of the shoot apical meristem (SAM), ultrastructure of its cells and the origin of primordia of organs in the SAM of horsetails Equisetum sylvaticum L. and E. fluviatile L. were studied. A relatively low degree of vacuolation and structural homogeneity of the cells that compose the surface initials zone (SI), the presence of single starch grains in their plastids and single lipid droplets in the cytoplasm of the SI cells were revealed. These features are more similar to those in the monoplex SAM of lycophytes than to those in leptosporangiate ferns. It is shown that initiation of leaves in E. sylvaticum and E. fluviatile via emergence of the leaf apical initials (LAIs) in the surface initials zone is similar to that of other plants with monoplex SAM; both ferns and lycophytes. The main peculiarity of organogenesis in horsetails is the origin of the leaf whorl as a single structure; each whorl develops from the triplet of the shoot apical initial merophytes. The inner cells of the emerging leaf whorl that belong to the single triplet of merophytes differentiate into the intercalary meristem. Each phytomer of E. sylvaticum and E. fluviatile is composed of the whorl of congenitally fused leaves and a whorl of buds that emerge in the axils of leaf bases located between the blades and thus alternate with leaves. Each bud bears a single root primordium; bud primordia develop on aerial shoots while root primordia – on the underground shoots. Termination of the leaf apical meristem functioning, that consequences from the vacuolation of the LAI, leads to the absence of the marginal meristem and the vascular tissues in the leaf blade. Proximodistal development of the leaf whorl and origin of buds results from meristematic activity of the peripheral part of the intercalary meristem. The search for the homologues of genes encoding known for angiosperms regulators of the development of adaxial (C3HDZ and ARP) and abaxial (YABBY and KANADI) leaf domains in available transcriptomes of horsetails and matching of the found homologues with that from the genomes of mosses, ferns and gymnosperms was undertaken in the context of assessment of presumptive regulatory similarities or differences of leaves of horsetails and other ferns in the context of leaf homology in the two groups. MEME analysis has shown that R2-R3 MYB proteins from transciptomes of horsetails are not ARP homologues. Thus it has been revealed that horsetail have single adaxial domain regulator (C3HDZ) and single abaxial domain regulator (KANADI), as other ferns. This finding suggests the probable loss of other regulators of the adaxial (ARP) and abaxial (YABBY) domains in the common ancestor of Polypodiophyta. Phylogenetic analysis of the identified homologues of genes that encode WOX proteins suggest that the T3 clade, that includes regulators of marginal (WOX3) and plate (WOX1) leaf meristems, originated in a common ancestor of Polypodiophyta, also indicating similarities in the molecular genetic regulation of the leaves in horsetails and other ferns.

The manifestation of sexual polymorphism in the sweet woodruff Galium odoratum was studied in the Moscow region during 2021–2023. The plant is a common perennial herbaceous, long-rhizome, polycarpic sciophyte. We find that at low illumination (less than 15% of total sunlight) only perfect flowers are formed. With increasing illumination (to up to 60% of full sunlight in clear weather), both perfect and staminate flowers are formed on individual plants. The perfect flowers of G. odoratum are complete, actinomorphic, tetracyclic, and heteromeric. In contrast, in staminate flowers the gynoecium is reduced, but its rudiments are preserved in the form of sterile stigmas and very short stylodia. Perfect flowers are significantly larger than staminate ones. The inflorescence in G. odoratum is a panicle-shaped monotelic, heterocladial, conjunctive thyrsus. Staminate flowers in andromonoecious individuals are located only on shoots of order IV, and their proportion varies from 12% to 30%. We finally discuss the possible reasons for the manifestation of andromonoecy in flowering plants under the influence of various environmental factors.

The “water–land” ecotone system is the coast of a reservoir from the water’s edge to the watershed. It is characterized by its landscape, soil properties, the hydrological regime of the land, the peculiarity of vegetation and the dynamics of biocomplexes. In the Sostinsky landscape area, located in the north-east of the Kumo-Manych depression, there is a large number of saline lakes drying up in the summer (Keltrikan, Kirkita, Khar–Erge, Sostinsky) and depressions. The vegetation of ecotones near these lakes is represented by halophytic dwarfsemishrubs (Halocnemeta strobilacei, Halimioneta verruciferae Caroxyleta dendroidis, Frankenieta hirsutae), annuals (Suaedeta acuminatae, Petrosimonieta oppositifoliae, Petrosimonieta brachiatae) and shrubs (Tamariceta laxae) communities.

The article presents data on the locality of Nymphoides peltata (S.G. Gmel.) Kuntze, a new species for the flora of the Leningrad Region. A rare alien species forms extensive thickets on Lake Nakhimovskoye (Vyborgsky District).

The memoirs of colleagues and excerpts from archival documents related to the life of Georgy Ivanovich Rodionenko served as material for this generalization. The name of Georgy Ivanovich is widely known among botanists of our country and all over the world. Georgy Ivanovich, first of all, is known to everyone as the creator of the Iridarium of the Botanical Institute. V.L. Komarov (RAS). For 35 years he was the scientific curator of the Iridaceae collection of the Botanical Garden of the BIN RAS. Thanks to his efforts, the BIN RAS Iris collection has become world famous.