Formation of the photosynthetic potential of potato in basic seed production using modern plant growth regulators

Abstract

Purpose. Study of the influence of plant growth regulators on the formation of the photosynthetic apparatus of potato plants in plantings of basic seed material in the conditions of the Forest-Steppe zone of Ukraine. Methods. Field (the experimental part was implemented by setting up a field experiment and performing regulated agrotechnical treatments), statistical – the results were analyzed using the MS Excel data analysis package. Results. The results of studies on the effect of growth regulators Raikat, Radifarm, and the fungicidal-bactericidal agent Farmayod on the photosynthetic activity of the Zhitnitsa potato variety are substantiated. The research was conducted under the conditions of the Forest-Steppe zone of Ukraine within the basic seed production system. The dynamics of leaf area formation, leaf area index and net photosynthetic productivity (NPP) during the growing season were investigated. It was established that the application of the studied products positively influenced leaf apparatus development and the intensity of dry matter accumulation. In different growth stages, various increases in assimilating leaf surface area were observed compared with the control treatment, within the following ranges: leaf development stage – 0.1–0.8 thousand m²/ha (2.0–16.3%); inflorescence emergence stage – 0.5–3.3 thousand m²/ha (2.9–19.5%); flowering stage – 0.5–5.0 thousand m²/ha (1.8–17.8%); haulm senescence stage – 1.0–3.3 thousand m²/ha (4.5–14.7%). The effectiveness of growth regulators in forming the leaf apparatus was lower at the beginning of the growing season compared with the inflorescence emergence and flowering stages. The highest efficiency was demonstrated by the combined application of Radifarm + Farmayod, which ensured the maximum leaf area values at the following development stages: leaf development (BBCH 10–19) – 5.7 thousand m²/ha; inflorescence emergence (ВВСН 50–59) – 20.2 thousand m²/ha; flowering (ВВСН 60–69) –32.8 thousand m²/ha; beginning of haulm senescence (BBCH 80–89) – 25.6 thousand m²/ha. Analysis of net photosynthetic productivity revealed a general trend toward its gradual decline across interphase periods; however, in all experimental treatments the values exceeded those of the control treatment. In particular, during the leaf development – inflorescence emergence stage, the daily increase in dry matter compared with the control treatment ranged from 0.2 to 2.1 g/m² per day; during the inflorescence emergence – flowering interphase period, net photosynthetic productivity (NPP) varied from 0.3 to 2.8; during the flowering – haulm senescence stage, the increase in NPP ranged from 0.8 to 3.7 g/m² per day. The highest NPP values were obtained in the Radifarm + Farmayod treatment, where the increase relative to the control treatment amounted to 2.1, 2.8, and 3.7 g/m² (18.4 %, 24.3 %, and 38.1 %), respectively, across the vegetation stages. It has been mathematically proven that the yield of the basic seed potato variety Zhitnitsa is determined by the development of the assimilation apparatus by 86.1 % (R2=0.86). The regression equation (y=0.2416x-1.0458) confirms that the intensification of photosynthetic activity through the use of growth regulators is a strategically sound measure, as it ensures a predictable increase in yield by optimizing the leaf surface and extending its active functioning period. Conclusions. The combined use of Radifarm and Pharmayod in plantings of basic seed material of the Zhitnitsa potato variety provides a synergistic effect, stimulating the formation of a powerful foliage system and the accumulation of dry matter. An important advantage of such treatment is the prolongation of photosynthetic activity due to the extension of interphase periods, which allows plants to more effectively realize their genetic potential.