Enhancing Sorghum Productivity with Methyur, Kamethur, 2 and Ivin Plant Growth Regulators †

: Sorghum is one of the most important food, fodder and technical crops grown in the

vironmentally friendly plant growth regulators Methyur, Kamethur and Ivin to improve growth and increase the productivity of sorghum, while reducing the use of environmentally toxic agrochemicals for plant protection and improving the environmental condition of the entire agricultural system.

Introduction
Sorghum (Sorghum bicolor (L.) Moench) is one of the important cereal food, fodder and technical crops grown in many countries around the world [1,2].Sorghum ranks fifth in the world after wheat, rice, corn and barley.Currently, sorghum is grown on almost all continents, over the past 50 years, the sorghum sown areas in the world amount to almost 44 million hectares [2].
The main advantage of sorghum is its high drought tolerance and unpretentiousness to soils, which makes this crop especially important in the context of global climate change [3].However, there are problems with growing sorghum under adverse environmental conditons; for this purpose, plant growth regulators are used to improve growth and increase productivity of sorghum [4,5].This article describes the results of our previous work [6], in which the effect of new plant growth regulators based on pyrimidine and pyridine derivatives, such as Methyur (sodium salt of 6-methyl-2-mercapto-4-hydroxypyrimidine), Kamethur (potassium salt of 6-methyl-2-mercapto-4-hydroxypyrimidine) and Ivin (N-oxide-2,6-dimethylpyridine), synthesized in the Department for Chemistry of Bioactive Nitrogen-Containing Heterocyclic Compounds, V.P. Kukhar Institute of Bioorganic Chemistry and Petrochemistry of the National Academy of Sciences of Ukraine, on growth and productivity of grain sorghum (Sorghum bicolor L.) cv.Yarona, and sweet sorghum (Sorghum saccharatum L.) cv.Favorite was studied in the field.

Materials and methods
The chemical structure and relative molecular weight of new plant growth regulators Methyur and Kamethur (derivatives of sodium and potassium salts of 6-methyl-2-mercapto-4-hydroxypyrimidine) and Ivin (N-oxide-2,6-dimethylpyridine are shown in Figure 1.Field experiments were carried out on grain sorghum (Sorghum bicolor L.) cv.Yarona, and sweet sorghum (Sorghum saccharatum L.) cv.Favorite.Seeds sterilized with 1% KMnO4 solution were treated either with distilled water (control sample) or with solutions of any plant growth regulators Methyur, Kamethur or Ivin, applied at a concentration of 10 -7 M for 24 hours (experimental sample).Each control and experimental sample contained 50 plant seeds.Then the soaked seeds were planted in the soil.The analysis of growth parameters: the average length of root (in mm) and the average fresh weight (in gram) of sorghum grown for 2 month in the field, and productivity parameters: the average panicle length (in cm) and the average fresh weight of grain (in gram) of sorghum grown for 4 month in the field was carried out according to the guidelines [7].Statistical processing of the data of the experiments performed in three replications was carried out according to the Student's-t variance test with a significance level of P≤0.05; the values are average ± SD [8].
The growth parameters (the average length of root (in mm) and the average fresh weight (in gram)) of sorghum grown for 2 month in the field and productivity parameters (the average panicle length (in cm) and the average fresh weight of grain (in gram)) of sorghum grown for 4 month in the field, determined in experimental samples of sorghum plants, were calculated as % in relation to similar indicators determined in control samples of sorghum plants      Summarizing the data obtained, it should be concluded that synthetic plant growth regulators Methyur, Kamethur and Ivin have a high stimulating effect on the growth and development of sorghum shoots and roots in the vegetative phase, as well as on the growth and development of sorghum panicles and grain formation in the reproductive phase.Obviously, their high growth-stimulating effect may be explained by their auxin-like and cytokinin-like effects on the processes of proliferation, elongation and differentiation of plant cells [9 -11].In addition, the composition of synthetic plant growth regulators has a positive effect on plant growth and development.A plant growth regulator Ivin contains the macronutrient nitrogen; Kamethur contains the macronutrients nitrogen, potassium and sulfur, which are necessary for plant growth and metabolism, and plant adaptation to biotic and abiotic stress factors [12,13].Plant growth regulator Methyur, containing the macronutrients nitrogen, sulfur and the chemical element sodium, promotes plant growth and productivity, as well as plant adaptation to salt and osmotic stress [14 -16].

Conclusions
The results of field studies confirmed the possibility of practical application of the new environmentally friendly plant growth regulators based on 6-methyl-2-mercapto-4-hydroxypyrimidine sodium and potassium salts (Methyur and Kamethur) and N-oxide-2,6-dimethylpyridine (Ivin) to improve the growth and increase the productivity of sorghum.Thanks to the use of these environmentally friendly plant growth regulators in a nanomolar, environmentally non-toxic concentration of 10 -7 M to treat seeds before planting in the soil, it will be possible to improve the growth and increase the productivity of sorghum and its adaptation to stress factors, while reducing the use of environmentally toxic agrochemicals for plant protection and improving the environmental condition of the entire agricultural system.

Figure 1 .
Figure 1.Chemical structure and relative molecular weight of plant growth regulators Methyur, Kamethur and Ivin.

Field
studies have shown that the growth indicators of experimental grain sorghum (Sorghum bicolor (L.) Moench) cv.Yarona exceeded that of control plants (Figure2, A, B and C).Root length (in mm) increased: by 15% -in plants treated with Kamethur, by 14% -in plants treated with Methyur, by 29% -in plants treated with Ivin, compared to the control.Plant fresh weight (in gram) increased: by 67% -in plants treated with Kamethur, by 53% -in plants treated with Methyur, by 21% -in plants treated with Ivin, compared to control.

Figure 2 .
Figure 2. Growth indicators of 2-month-old grain sorghum (Sorghum bicolor (L.) Moench) cv.Yarona grown in the field: A -root length (in mm), B -plant fresh weight of (in gram), C -sorghum roots.Growth indicators of experimental sweet sorghum (Sorghum saccharatum (L.) Moench) cv.Favorite exceeded that of control plants (Figure3, A, B and C).Root length (in mm) increased: by 20% -in plants treated with Kamethur, by 40% -in plants treated

Field
studies have shown that the yield indicators of experimental grain sorghum (Sorghum bicolor (L.) Moench) cv.Yarona exceeded that of control plants (Figure 4, A, B and C).Panicle length (in cm) increased: by 7% -in plants treated with Kamethur, by 20% -in plants treated with Methyur, by 17% -in plants treated with Ivin, compared to control.Grain fresh weight (in gram) increased: by 22% -in plants treated with Kamethur, by 26% -in plants treated with Methyur, by 13% -in plants treated with Ivin, compared to control.

Figure 4 .
Figure 4. Yield indicators of 4-month-old grain sorghum (Sorghum bicolor (L.) Moench) cv.Yarona grown in the field: A -panicle length (in cm), B -grain fresh weight (in gram), C -panicles with sorghum grains.Yield indicators of experimental sweet sorghum (Sorghum saccharatum (L.) Moench) cv.Favorite exceeded that of control plants (Figure 5, A, B and C).Panicle length (in cm) increased: by 36% -in plants treated with Kamethur, by 37% -in plants treated with Methyur, by 25% -in plants treated with Ivin, compared to control.Grain fresh weight (in gram) increased: by 24% -in plants treated with Kamethur, by 38% -in plants treated with Methyur, by 35% -in plants treated with Ivin, compared to control.