Intensification of cultivation of Pinus sylvestris L . seedlings with a closed root system in the Southern Urals

. The article presents the results of research on growing seedlings of Pinus sylvestris L. with a closed root system in a greenhouse when sowing in cassettes, on three types of substrates and 7 variants of pre-sowing treatment with various growth stimulants, which affected the energy of seed germination and germination, and also on increasing the total number of germinated seeds during the first month. Good germination results were obtained when seeds were treated with Borogum-M, Bogatyi-Micro, Bionex-Kemi preparations in low-density peat, filled with the starting composition of fertilizers. But in the subsequent period, the development of seedlings was more intense on denser peat with the addition of humic acids and salts, mineral fertilizers, trace elements, strains of soil microflora and mycorrhiza. Biometric indicators of seedlings also turned out to be slightly higher on this substrate. It is proposed to grow pine seedlings during one growing season on low-density peat with the addition of a complex of components.


Introduction
Growing coniferous seedlings with a closed root system in recent years has become quite a common way of growing planting material for the renewal of forests [1][2].At the same time, studies are being conducted to determine the influence of various factors on the acceleration of the cultivation of planting material with the release of healthy plants [3].Various containers for cultivation are being tested [4], natural and artificial substrates [5][6][7].The influence of growth stimulators [8][9], pre-sowing preparation of seeds [10][11][12] fertilizers at different stages of seedling development [13][14][15] and the importance of irrigation [16] are studied.To increase stress resistance, seedlings are grown with the addition of spores and cultures of ectomycorrhizal fungi to the substrate [17][18].
In the Republic of Bashkortostan, several forestry managements are engaged in the cultivation of Pinus sylvestris L. in cassettes for reforestation.It is necessary to develop a standard approach to growing pine seedlings in the conditions of the Republic of Bashkortostan in the Southern Urals.At the same time, it is necessary to intensify the process of growing seedlings.
The purpose of the research is to identify the most high-quality substrates and methods of pre-sowing seed treatment with the use of growth stimulants, the selection of the optimal system of fertilization of seedlings of the first year for the cultivation of high-quality viable planting material.

Materials and methods
In April 2022, Pinus sylvestris seeds were sown after stratification by the method of snowing (February-April 2022).Seeds were collected in the Angasyak forestry of the Dyurtyulinsky district of the Republic of Bashkortostan in November 2021 from mediumaged trees of the I class of Bonitet, the weight of 1000 seeds is 6.26 g.RKL-81 cassettes were used for sowing seeds, the cell size is 4,1x4,1x8 cm, the cell volume is 90 cm3, there are 81 cells in one cassette.
Before sowing, the seeds were soaked in stimulant solutions for 2.5 hours, then in a TMDT fungicide (control) and Phytosporin (1.5 hours, all experiments).

Phytosporin is a symbiotic bacterial culture of Bacillus subtilis strain 26D (2×109 live cells and spores per 1 g).
There were 6 variants of experiments and one control variant.In the numbering of experiments, the first digit is the preparation for soaking seeds, the second digit is the type of substrate.
The seedlings were grown in a greenhouse with an automatic irrigation system.The cassettes were installed on metal frames, at a height of 20 cm. from the greenhouse floor, with air access to the cassette cells.
After the emergence of seedlings, the seed germination energy was determined (the percentage of germinated seeds in 10 days), germination (the percentage of normally germinated seeds on the 14th day after sowing).To control the growth dynamics of seedlings, height measurement was carried out every 10-15 days during the entire vegetative period.Biometric indicators (presence of mycorrhiza, roots length, height of the aboveground part of the seedling, absolutely dry root mass, weight of the aboveground part of the seedling) were determined in September.The degree of mycorrhization of the root system was estimated in points: 1-weak mycorrhization -from 10 to 30% of the root ball of the seedling, 2-mycorrhization from 30 to 50% of the root ball, 3-mycorrhization of more than 50% of the root ball.

Results
The seeds sowing were carried out on April 22.The germination energy was determined on May 2. The germination of seedlings was determined on May 6.In mid-September, a selective biometric study of seedlings was conducted.In 50 seedlings from each variant of the experiment, the height of the aboveground part and the length of the root were measured (Figure 2).
The absolutely dry biomass of the seedling, the biomass of the aboveground part and the biomass of the root were also determined (Figure 3).
The diameter of the Stem was measured, the degree of mycorrhization of the roots was determined and the number of seedlings that developed lateral shoots was revealed (Table 1).

Discussion
The highest germination energy (26-41%) and seed germination (41-62%) were revealed in the experimental variants on substrate 2 with pre-sowing seed treatment with preparations Borogum-M, Kornesil, Bogatyi-Micro.Bionex-Kemi.This is also due to the lower density and greater air conductivity of substrate 2, compared to substrates 1 and 3.
In the first month of observation, the highest growth rate (0.14-0.16 cm/day) revealed in the variants of the experiment on substrate 2 and 3 (pre-sowing seed treatment of GUMI-20, Borogum-M, Bogatyi-Micro, Bionex-Kemi).However, in the second month of observations, a higher growth rate was noted already on substrate 3 (0.08-0.1 cm/day).In July and August, this trend continued.The growth rate of seedlings in most variants was similar to the curve of a large period of Sachs ' growth (S-shaped curve) [19]: an intensive start of growth, a slight slowdown, then again intensive growth from mid-June and its slowdown in August.The average growth rate over the entire observation period turned out to be high in the variants of the experiment on substrate 3 (0.09 cm/day).Due to growing in a greenhouse, the development period of seedlings has increased somewhat, since in the open ground there is a cessation of growth in height already in mid-August [19].Analysis of the biometric parameters of seedlings in September showed that the highest average height of the aboveground part of seedlings (12.2-13 cm) was revealed in the experimental variants on substrate 3, the variants on substrate 2 (4.2, 7.2) showed an average height of 12 cm, which also exceeds the recommended height values for two-yearold pine seedlings [20].
To assess the quality of pine seedlings, it is important to take into account the ratio of aboveground and underground biomass [19].The optimal ratio is: 2:1.The lowest ratio of aboveground and underground biomass (1.8:1) was found in the experimental variants on substrate 3 and 2 (1.3, 3.2), the ratio of 2:1 -in variants 5.3 and 6.2., the ratio of 2.55:1 -in Seedlings grown on substrate 3 and most variants on substrate 2 have a stem diameter slightly larger than 0.2 cm.The average value of the diameter of the stems according to the experimental variants showed a positive correlation with the weight (0.87) and height of the aboveground part of the seedlings (0.87), with the degree of mycorrhization of the roots (0.81), with the weight of the roots (0.77), the presence of lateral shoots (0.67).
A high degree of mycorrhization on the roots of seedlings(3 points) was detected on substrate 2 and 3.
A positive correlation of the degree of mycorrhization of the root system with the height of seedlings (0.8), with the biomass of the aboveground part of seedlings (0.72), with the number of lateral shoots (0.7) was revealed.
Thus, the germination and the starting growth rate in May turned out to be higher in the variants of the experiment on substrate 2 when using various growth stimulators in presowing seed treatment.The option 4.2 (pre-sowing treatment of Borogum-M, similarly: 5.2, 6.2, 7.2) stands out especially strongly.The importance of boron for the growth and development of conifers is great [21][22], especially during the period of seedling growth activation, and pre-sowing seed treatment with humates also significantly accelerates the development of seedlings in the first month [12].The rapid growth of seedlings in the first month on substrate 2 is also associated with the optimal amount of nutrients introduced into the peat before sowing, with a lower density and greater air conductivity of substrate 2, compared with other substrates.
However, subsequently, seedlings growing on substrate 3 showed more intensive growth and formation: a greater height of the aboveground part, root length, biomass, stem diameter, the presence of developed lateral shoots.The optimized composition of substrate 3, containing not only mineral and organic fertilizers, sodium humates, trace elements (B, Cu, Mo, Zn, Mn), but also cultures of strains of friendly microorganisms, live mycorrhiza,

Conclusion
The conducted researches have shown that pre-sowing seed treatment of seeds with growth stimulants affects the germination energy, germination ability and growth rate of Pinus sylvestris seedlings in the first month after germination.Pinus sylvestris seedlings germinate especially intensively during pre-sowing seed treatment with Borogum-M, Bionex-Kemi, Bogatyi-Micro preparations on a loose substrate (on peat with a lower density) filled with starting mineral fertilizers (substrate 2).
However, in the subsequent period, from June to September, the composition of the substrate becomes decisive in the development of seedlings.The best indicators of growth and development of seedlings were found on substrate 3.
When sowing stratified Pinus sylvestris seeds in RCL-81 cassettes in substrates 2 and 3, by September seedlings reach the recommended biometric indicators for two-year-old Pinus sylvestris seedlings and slightly exceed them.An important indicator for assessing the quality of seedlings is the ratio of aboveground and underground biomass, which in half of the experimental variants on substrate 2 and 3 turned out to be within 2:1 (2.5:1).
Thus, the intensification of the development of Pinus sylvestris seedlings can be achieved by pre-sowing treatment of stratified seeds with Borogum-M, Bionex-Kemi, Bogatyi-Micro preparations and filling cassettes with looser peat (with a total density of 0.3 g / cm 3 ) with the addition of humic acids and salts, mineral fertilizers, trace elements, strains of friendly soil microflora and mycorrhiza.This will increase the germination energy, seed germination, and with regular foliar and root fertilizing in one season, get high-quality planting material with a well-formed root system with a high degree of mycorrhization, stems with optimal height forming lateral shoots.

Fig. 2 .
Fig. 2. The average height of the aboveground part and the root length of seedlings of Pinus sylvestris 15.09.2022.

Fig. 3 .
Fig. 3. Average weight of the aboveground and underground parts of Pinus sylvestris seedlings 15.09.2022.

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010 (2023) BIO Web of Conferences CIBTA-II-2023 https://doi.org/10.1051/bioconf/2023710100303 71 contributed to more intensive growth and development of seedlings from June to the end of August.

Table 1 .
, 2.2, 4.2, 2.3, 4.3, 3.3.In the variants of experiment 6.3, 7.3, 7.2, a ratio of 3:1 was revealed, which indicates a lag in root growth relative to the above ground part.Stem diameter, the degree of mycorrhization of the roots and the presence of lateral shoots in Pinus sylvestris seedlings.