Nadezhda Igorevna Uyutova

Spring rapeseed is one of the most important oilseed crops worldwide. Currently, one rapeseed development cycle takes about five to six months. Shortening the growing season can significantly reduce the growing period and speed up the realization of breeding and research projects. This could allow up to four generations of rapeseed instead of two or three under greenhouse conditions. Our research was conducted in 2023–2024 in a two-section climatic chamber developed at Federal Scientific Agroengineering Center VIM. The aim of the study was to study the effect of accelerating the growing season of rape by increasing the photoperiod and using different spectral composition of light. The experiment was conducted in 4 variants: Variant 1(22/2 RB) — photoperiod 22 h day / 2 h night and spectral composition R:40/B:60 (red-blue spectrum only); Variant 2 (22/2 FS) — photoperiod 22 h day / 2 h night and full spectrum FS (UV0.5: B37: G6.5: Y3: R49: FR4); Variant 3 (16/8 RB) — photoperiod 16 h / 8 h night and spectral composition R:40/B:60 (red-blue spectrum only); Variant 4 (16/8 FS) (control) — photoperiod 16 h day / 8 h night and full spectrum (UV0.5: B37: G6.5: Y3: R49: FR4). We achieved a reduction in growing season by 14 days using an extended photoperiod (22-hour daylight hours) and full spectrum radiation (UV0.5: B37: G6.5: Y3: R49: FR4). It was found that variants 1 and 2 used in the experiment could be used to obtain rape seeds of proper quality. The best was variant 2–22/2 FS using 22 hour daylight hours and full spectrum radiation (UV0.5: B37: G6.5: Y3: R49: FR4).

Lighting conditions are an important controller of plant growth and development, and they affect secondary metabolite synthesis. In this research, we explored the effect of additional UV irradiation of various ranges in addition to the main one at PPFD 160 µmol m⁻² s⁻¹ on the accumulation of some secondary metabolites of stevia (Stevia rebaudiana Bertoni). The fresh weight of leaves was slightly higher under additional UV-A and UV-B irradiation compared with the control variant, and the leaf surface area was significantly larger, respectively, by 23.3 and 20.7% than in the control variant, while the rate of photosynthesis did not decrease. Plants under additional UV-B and UV-C irradiation were under the greatest light stress, as evidenced by a decrease in antioxidant capacity by an average of 30% compared to the control and UV-A. The total flavonoid content was significantly higher (by 74%) under UV-B irradiation. The highest concentration of steviol glycoside was observed during budding and flowering under UV-B and UV-C irradiation (by 13.2 and 11.3%, respectively). Analysis of hyperspectral images, chlorophyll fluorescence, and vegetation indices showed light stress increasing under UV-C irradiation, which caused an increase in the relative chlorophyll content, scorches, leaf morphology changes, a CO₂ absorption rate decrease, and plant growth inhibition. UV-B irradiation can be used as an optimal type of irradiation based on a set of indicators.

The present study has been carried out to determine the effects of four different illuminators with red, far-red, blue, and white light-emitting diodes (LEDs) on the growth, morphology, pigment composition, and chlorophyll fluorescence of spinach (Spinacia oleracea L.) of the ‘Zhirnolistny’ cultivar. We investigated these variants in two photon flux densities, 400–800 nm (PFD) 120 µmol m⁻² s⁻¹ and 180 µmol m⁻² s⁻¹. The studies were carried out in a climate chamber. Plant measurements were carried out on the 30th and 45th days of cultivation. The results showed that during the period of active growth, on the 30th day, spinach plants accumulated 2.6 and 2.4 times more fresh weight in the variant with a higher PFD (180 µmol m⁻² s⁻¹). At the end of the growing season, only a decrease in PFD had an effect on the fresh and dry weight of plants. The highest concentration of chlorophyll on both the 30th and 45th days of vegetation was found when spinach plants were grown under red-blue (RB) LEDs in a spectrum proportion of R70:B30. It was found that the variants had a higher proportion of green radiation in the spectrum of illuminators with PFD 180 µmol m⁻² s⁻¹, and the nitrate content in spinach was slightly lower than in other variants.