Ecological and biological features of Primula macrocalyx Bunge in nature and culture in the south of the Tomsk region

In Siberia, there is a noticeable decrease in the number and occurrence of Primula macrocalyx, which is mainly associated with increased anthropogenic pressure, leading to the degradation of vegetation cover over large areas and the destruction of its habitats. At the edge of its range, many localities of this species are so fragmented and small that there is a danger of their complete destruction. Therefore, P. macrocalyx is rightfully included in the lists of protected species in the Republic of Buryatia, Irkutsk, Kurgan, Tyumen and Tomsk regions, which determines the relevance of conducting natural and introduction studies of this species. The purpose of this research is to study the ecological and biological characteristics of P. macrocalyx in the south of the Tomsk region in nature and culture in connection with the prospects for practical use and protection. Population studies were carried out on the right bank of the Tom river in the vicinity Anikino town and Blue Cliff (Tomsk region). The study area is part of the Kolyvan-Tomsk folded upland and is located at the junction of the Altai-Sayan mountain region and the West Siberian Plain. Identification of the phytocenotic location of cenopopulations and population studies were carried out using traditional geobotanical approaches and approaches adopted in modern plant population biology. Material for introduction studies was used in the 90s - early 2000s in the form of plants and seeds from natural habitats in the vicinity of Tomsk, plants grown from seeds were planted at the introduction site of the Siberian Botanical Garden, TSU. The study of reproductive biology was carried out in accordance with generally accepted methodological developments. Descriptive analysis was used for statistical processing of the obtained data. Comparison of indicator values for different years was carried out using one-way analysis of variance ANOVA. In the south of the Tomsk region, P. macrocalyx is found in mixed-grass birch and mixed forests confined to well-drained areas on the right bank of the Tom river (See Fig. 1). Among the herbage, individuals are distributed unevenly and do not form dense clusters, standing out noticeably only in the spring during mass flowering. Coenopopulations are characterized by low ecological and effective densities, which are 6.9 (CP 2) - 8.4 (CP 1) ind./m2 and 1.6 (CP 1) - 2.5 (CP 2) ind./m2, respectively (See Table 1). The ontogenetic structure of the coenopopulations is represented by almost all age groups; there are no individuals in the senile state. In the age composition, bimodal and left-sided types of ontogenetic spectra are formed. Coenopopulations are normal, incomplete, young, individuals of the young fraction predominate (66-79%). The significant participation of individuals of the pregenerative period (j-v), constituting 49% (CP 1) - 63% (CP 2), indicates regular seed renewal, which ensures the self-sustainment of the species. There is also a noticeable accumulation of plants of the generative fraction (g1-g3) - from 36% (CP 2) to 47% (CP 1), which is associated with a long period of development of individuals of this age period. In general, the ecological and phytocenotic conditions of the species' habitats on the northern border of its range in the Tomsk region favorably affect the development of individuals of the young fraction. This allows Tomsk coenopopulations to be assessed as stable, but annual monitoring is required to identify the degree of influence of anthropogenic factors. When introduced, P. macrocalyx retains the main biological features characteristic of this species in natural habitats. According to the phenorhythmic type, it is a spring-summer-winter green species, with long flowering and regular fruiting. The average duration of the growing season in Tomsk, based on the results of 25 years of research, is 183 days. The reproductive success of the species is ensured by the effective functioning of a multi-stage system of reproductive structures. Quite large, brightly colored flowers are clearly visible to pollinating insects. The average sizes of pollen of the short-columnar form are 1.5-1.6 times larger than the pollen grains of the long-columnar morph (See Figs. 2 and 5). High quality of mature pollen ensures efficient pollination and production of high-quality seeds (See Figs. 3, 4 and 6). The relatively low year-to-year variability of the real seed productivity (303.6-435.9 seeds per shoot) and productivity coefficient (41.8-65.4%) indicators allows for a stable seed yield under crop conditions (See Table 2). When sown, freshly harvested seeds of P. macrocalyx have a germination rate of 6.7-22.0% or do not germinate at all due to the presence of deep endogenous dormancy. One of the effective stimulators for the release of seeds from dormancy (after 7-8 months of dry storage) is long-term (2.5 months) cold stratification at temperatures from +3 to +5°C, after which the average seed germination was 54.161.4%. Treatment in a 0.1% solution of gibberellic acid effectively increases seed germination to 86.7-97.3%. After 2.5 years of storage, seed germination is reduced by more than half and is already 36.7-45.3%. When stored for 3.5 years, seeds after cold stratification had an average germination rate of only 16.7%. The period of cultivation under cultural conditions in one place without division can be 3-4 years. If cultivation practices are followed, P. macrocalyx is resistant to biotic factors. Signs of fungal diseases may be noted on plant leaves, but they do not have a significant effect on the condition and decorative qualities of introduced plants. The high winter hardiness and stability in culture of P. macrocalyx is associated with its geographical origin and biological characteristics. The results obtained can be used for the purpose of introduction into ornamental and medicinal plant growing, as well as for preserving the biodiversity of the region by reintroducing the species into natural phytocenoses in the Tomsk region. The article contains 6 Figures, 2 Tables, 57 References. The Authors declare no conflict of interest.

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