The influence of different light sources on photosynthetic performance and productivity of Cucumis sativus L. hybrid Tristan F1 in aeroponic phytotron facilities

Global climate change and anthropogenic pollution of the environment pose serious problems for agricultural producers. Drought or flooding of fields, the emergence of new diseases and pests, and reduction of agricultural land pose serious problems in providing food for the growing population. Moreover, more than half of the world’s population lives in cities, and this proportion is expected to increase to 67 % at 2050. To meet the growing needs of the population of megacities, new non-standard approaches and technologies are needed to increase the production of fresh vegetables, fruits, and berries. Vertical plant growing in the so-called “city farms” is a promising resource-saving method of compact multi-tier cultivation of various plants, especially greens, vegetables, medicinal and ornamental plants. The use of hydroponics and aeroponics allows a new type of agriculture that combines biotechnology, industrial architecture, design and successfully integrates into urban infrastructure. A significant increase in the production and yield of basic food vegetable crops, especially in “city farms” necessitates understanding needs of plants for light, mineral nutrition and other equally important factors, e.g., temperature, humidity, CO2 content. Under the conditions of a phytotron that imitates a “city farm” model, we compared the effects of high-pressure sodium lamps (HPSLs) DNaT-600 traditional for greenhouse plant lighting and alternative light-emitting diode phytolamps (LEDs) on photosynthesis and, ultimately, the production process in Cucumis sativus L. Tristan F1 hybrid as a cucumber crop usually cultivated in greenhouses. In treatments 2 and 3, LED irradiators and DNaT-600 lamps at a radiation intensity of 305 and 413 mmol photons∕m-2∕s-1 and a temperature of 25 and 26 °С, respectively, provided formation of an effective photosynthetic apparatus capable of performing at an increase in light intensity up to 1200 mmol photons∕m-2∕s-1. The LEDs of treatment 2 can serve as a single light source when growing cucumbers in a “city farm”. These irradiators are characterized by a smaller proportion of blue (λmax = 450 nm) and far red (λmax = 730 nm) light and a larger proportion of red (λmax = 660 nm) light in the spectrum. However, for early harvesting, the DNaT-600 lamps with the standard plant lowering method are preferable. The period of growing plants under DnaT-600 irradiation in the “city farm” simulating aeroponic phytotron with a limitation of the phytolamp height of 1.5 m without plant lowering, ended 12 days earlier than under LED irradiators. Nevertheless, the yield during the growing season was higher for DNaT-600 than for LED irradiators with the same energy consumption. The data obtained are helpful in the design and creation of modern biotechnological enterprises, such as vertical “city farms” for the food production and biotechnological enterprises for production of biopharmaceuticals.