Home – Home – Jornals – Flora and Vegetation of Asian Russia 2021 number 4

The seed coat structure or exotesta was first studied in the following species Trollius apertus Perf. ex Igoschina, T. ranunculinus (Sm.) Stearn (section Trollius Doroz.), T. sibiricus Schipcz. (section Longipetala Doroz) and T. riederianus Fisch. et C.A. Mey. (section Insulaetrollius Doroz.). In the paper, there is presented the analysis of our long-term data on seed coat structure variability in 13 samples of T. asiaticus L. (section Longipetala Doroz.) collected in different parts of the area. The seeds are angular, ribbed-scrobiculate with cell of the same tri-hexahedral shape and straight anticlinal walls. The seed coat is smooth, exotestal; aerenchyma is formed by inner layers of the outer integument, while tegmen is formed by inner integument. In the cross-section, the aerenchyma is 28-40 mm thick; other layers get squished and flatten by full ripeness. At the convex side of seeds, aerenchyma is 5-8 mm thick and tegmen - 4-7 mm. Cross-section of ripe seeds shows a vertical hollow in the center of each exotesta cell. The hollow is 2-5 mm wide in its narrowest part and air fills it in the process of cellular protoplast withering away, which takes place usually at the wax ripeness stage. The spermoderm analysis by electron microscopy was conducted in longitudinal section as well. The description of seed coat sculpture by scanning electron microscopy (SEM) was carried out according to W. Barthlott (1981). Additionally, there are described cross-sections and the average scheme of the structure is given. The spermoderm surface morphology is represented by the primary sculpture in T. apertus and T. ranunculinus species. The tertiary sculpture is observed as a discontinuous wax coating in T. asiaticus and T. sibiricus, and as a complete one in T. riederianus. In all the species under the study, wax coating does not obscure the primary sculpture traits. In all Trollius genus representatives, the seed coat secondary sculpture is not expressed. We have refined the specific terms which describe the seed coat of Trollius species. The common consistent patterns of the genus have also been revealed. Significant polymorphy of seed coat structure characters was established in T. asiaticus plants from different regions; and their variability was evaluated in samples collected from the same populations in 2017-2020 years. The study of seeds from natural populations of the Sakha Republic and the Altay Republic allows to conclude that plants growing in the most remote from each other geographic regions range mostly in the entirety of the characters. The difference is found maximum in plants from the edges of the species area. Most seed coat structure characters appear to possess rather high plasticity not only within population sampling but even in one single seed, thus they cannot be applied for species diagnostics. SEM shows the form of exotesta cells as the most variable. It depends on the seed ribbing, so we recommend to describe the cells of the convex surface only. To characterise the seed coat in Trollius species we highlight more or less stable traits which demand further study in other representatives of the genus. Relatively constant characters of the spermoderm surface are presence or absence of axial strands formed by exotesta cells due to their flattening in one direction, and the colour and budge of the structural element center. By the cross-section there should be checked the shape of the air hollow and the air bubble presence above it.