Conducting research on the experimental site of the Volgograd region of the Southern Federal District allowed us to identify the most heat- and drought-resistant varieties, despite the extreme conditions of soil leaching along the slope steepness, as well as due to heavy rains (
Kostin, 2018;
Sukhova, 2019).
The soil relief at this experimental site consisted of large fractions of granulometric composition and a humus-depleted fertile layer of 0-10 cm -1.2%. In this regard, field germination was 15 days after sowing, on average 46 to
-52 plants/m
2. Consequently, this number of plants from the seeding rate of 3.5 million pcs/m
2 was due to the factor of an initially critical lack of nutrition at the experimental site (
Perekrestov, 2019).
Considering that the research was conducted with an emphasis on the genetic data of spring barley varieties and on resistance to extreme hot and arid conditions in the spring and summer period of the Volgograd region, studies were conducted on the photosynthetic potential and activity of chloroplasts in barley nutrition elements.
The temperature regime and amount of precipitation in March 2022 (179 mm) made it possible to obtain full shoots two weeks after sowing. At the end of May 2022, heavy rainfall occurred. Unfavorable conditions associated with high temperatures in the first ten days of June 2022, observed during the booting phase, slightly slowed down the development processes of spring barley plants, however, from the second ten days of June (before the start of the flowering phase), short-term precipitation fell, which allowed spring barley plants to form full-fledged grain. In March 2023, positive dynamics of daytime temperatures were established, but negative ones were observed at night, with an average monthly temperature of 2.30ºC. In March, 147 mm of precipitation fell in the form of rain and snow, this replenished the moisture supply in the upper layers of the soil. In April, there was a gradual increase in air temperatures, but at night, recurrent night frosts were recorded. The average temperature for April was +8.40 C and 62.6 mm of precipitation fell. The climatic conditions of the experimental site in the first ten days of May for sowing spring barley were favorable in terms of temperature, but later extreme temperature changes were observed due to prolonged rainfalls. The average monthly air temperature is 15.10ºC. During this period, 51.4 mm of precipitation fell. In June the weather was clear and hot. In the first ten days there were heavy rains, totaling 58 mm. The maximum air temperature reached +32.00ºC. In July the heat increased to +380ºC and there was little precipitation-14.5 mm. Heavy rainfall for 2022-2023. had a positive effect on the development of productive tillering, root mass and shoot mass of each variety of spring Barley (
Guzenko, 2022).
In the process of research site have shown that already at the early stages of ontogenesis, different varieties of spring barley have differences in the size of the leaf apparatus, depending on the characteristics of each variety.
The Kamyshinsky variety 23 with a result of 581.5% had the best indicators in terms of the volume of leaf surfaces in the phase period “tillering-earing”, however, Dmitrievsky 5 also showed itself with a slight difference, the difference was 35-to 48 thousand m
2 day/ha (Table 2).
A concomitant indicator of PP is, as previously indicated, the purest photosynthetic productivity, which is noted on the Kamyshinsky variety 23. Also, from spring barley, there was a slight decrease in NPP from the leading variety, Dmitrievsky 5 - by 0.23 g/m
2 (Table 3).
Further studies have shown that the active accumulation of absolute dry matter occurs in the “exit into the tube” phase and amounts to the maximum amount in Kamyshinsky 23 varieties - 480 g/m
2 (Table 4).
The analysis of chloroplast isolation and optical density measurements in this area between the varieties was also carried out and showed a weightless difference in the lack of elements in plants.
During the development of barley in the “tillering-booting” phase, the movement of chloroplasts in plant leaves and the supply of plant nutrients was studied using a mobile laboratory to carry out functional diagnostics using the express “Ecotest 2020” method.
The purpose of the invention is to rank the level of nutritional elements required by the plant - the “response” of the wavelength of chloroplasts to the studied nutrients of spring barley varieties. Using dispersion quantitative analysis of each diagnosed element, the significance and amount of nutrient reserves during the movement of chloroplasts are assessed (
Dolgopolova, 2019). The value (percentage) of the response is determined by the difference in the photochemical activity of the chloroplast suspension when diagnosing nutrients in the finished chloroplast suspension. This method made it possible to adjust the need for plant nutrients responsible for drought resistance of spring barley varieties: phosphorus, potassium, nitrogen, zinc, copper and others. For analysis, we used 3-4 leaves (from the top) of adult plants in the tillering phase (April 29, 2022 and May 6, 2023).
The study of the movement of chloroplasts by nutrition elements in the varieties of the Federal Research Center of Agroecology of the Russian Academy of Sciences showed that a high percentage of deviation from the control measurement “K2 - K3 - K4 - K4 - K5” was in Medicum 139 and Medicum 200 within ± 9
-to 14%. The smallest deviation in the range of 4
-5% for all food elements was in the grades Kamyshinsky 23 and Dmitrievsky 5 - on average 3-5% (Fig 2).
Based on the data obtained on the content of nutrients in extreme soil and climatic conditions with a small supply of humus, the following varieties proved to be the most stable: Kamyshinsky 23, Novonikolaevsky and Dmitrievsky 5 (Fig 2).
Summing up the leaf diagnostics, further research at the experimental site in the Kamyshinsky district allowed us to identify the most heat- and drought-resistant varieties, despite extreme conditions and soil relief consisting of large fractions of granulometric composition and depleted with humus, these are: Kamyshinsky 23 and Dmitrievsky 5 (Table 5).
The productive stem growth by varieties was on average in the range of 147-152 pcs/m
2, but the most progressive number of stems was calculated by varieties: Kamyshinsky 23-178 pcs/m
2 (Table 5). Other varieties had a lower productive stem from the two previous varieties by an average of 8-12% (Table 5). Based on the data obtained on the content of nutrients in extreme soil and climatic conditions with a small supply of humus.
As in the previous above-mentioned indicators, the leading varieties in yield are Kamyshinsky 23 (1.23 t/ha) and Dmitrievsky 5 (0.93 t/ha). The lowest values were obtained from Medicum 139-0.65 t/ha (Table 6).
Based on the verification of spring barley in the tillering phase for the potential of chloroplast activity in plant leaves (3-4 leaves), a trend model of cultivated varieties in the soil-climatic zone of chestnut soils with a humus content of 1.2% (Variable-X) was developed. The actual yield (Variable-Y) was taken as the main indicator of the potential of spring barley varieties. The reliability of the obtained trend line equations is confirmed by the approximation value (R
2), or the so-called coefficient of determination, which shows the degree of compliance of the trend model with the initial data. When conducting an approximation analysis, Kamyshinsky 23 varieties (R
2=0.63) obey the polynomial equation (Table 7), which shows the instability of the movement of chloroplasts in plant leaves, the stability of further development of barley in the phases of vegetation, which can lead to average yield stability of this variety (Table 7).
Based on data on other varieties, such as: Dmitrievsky 5 (R
2 = 0.74) and belongs to the exponential form of the equation - y = 23,322e
0202x (Table 7), which shows an increase in the movement of chloroplasts due to the nutrients contained in spring barley plants. It shows the presence of high activity of the green matter of spring barley plants due to the genetic characteristics of the variety and resistance to this area of the climatic zone.
This has also been demonstrated in a variety of substrates (hydroponics, growing pots and limestone soil). those old varieties of Scottish barley (Bere barley), which are better at absorbing and accumulating Mn, are better able to maintain the state of the photosynthetic apparatus compared to modern elite lines
(Schmidt et al., 2019). Given that increasing the efficiency of photosynthesis is now considered a key strategy for increasing yield
(Parry et al., 2013; Long et al., 2015), the effectiveness of microelements on other CO
2 indicators is also determined by the application of various root and foliar fertilizers, but genetic resistance in our studies showed a huge role in the drought resistance of plants to high hot temperatures.
