Supplemental LED interlighting on the physiological response and yield of mini-cucumber

• Ano de defesa: 2017
• Autor(a) principal: Quesada Roldán, Gustavo Alberto
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Cucumis sativus; Cucumis sativus L.; Artificial lighting; Cost; Curvas de resposta; Iluminação artificial; Performance; Photosynthesis; Postharvest; Rendimento; Response curve
• Link de acesso: http://www.teses.usp.br/teses/disponiveis/11/11136/tde-22032018-131951/

On the protected horticultural industry, the artificial lighting is a common practice under reduced natural light radiation or self-shading of the leaves at lower canopies. Those conditions affect the photosynthetic activity and the yield is limited. In the last decade, the use of lamps with LED technology for supplemental lighting has increased on high-latitude countries. LED lights are more energy efficient and have lower power consumption. On these lamps is possible to regulate the intensity (quantity) and the radiation (quality) on the ideal range of light spectrum in order to convert the luminous energy into chemical energy. Not reports of use of this technology were found at the tropics. Thus, the objective of this work was to evaluate physiological parameters related with the photosynthetic activity and the yield on mini-cucumber plants grown on protected environment with supplemental LED interlighting. At Piracicaba (Sao Paulo), Brazil, three experiments were conducted on LED interlighting equipped greenhouse, two at winter seasons (2015 and 2016 years) and one at summer season (2017 year) using mini-cucumber hybrid Larino. Through the three stands, was verified an increase on the photosynthesis in the leaves and the commercial productivity of the mini-cucumber due to the LED lighting use. This increase on the commercial yield ranged between 13 and 30%, being higher the effect on the summer season. At the first stand, in addition to the light effect, grafted plants were tested. On this case, the photosynthetic rate increased with grafted plants when treated with LEDs. However, the yield did not increase with grafting. Postharvest parameters as titratable acidity, total soluble solids and long shelf life did not increase as consequence of supplemental LED lighting. Studying the light response curves, it was verified that above a photosynthetic photon flux density of 400 μmol m-2s-1, plants treated with supplemental lighting showed higher values of net CO2 assimilation. The light compensation point was also higher on plants with LEDs. In the case of the CO2 response curve, plants treated with LED lighting verified higher increase on the CO2 assimilation rate when the plant internal CO2 concentration increased. Parameters like Rubisco carboxylase activity, rate of electron transport and leaf dark respiration were also higher on plants under supplemental LED lighting. The lower consumption of electricity and the yield increase on the summer stand allowed registering greater energy and light efficiency on this cycle when compared with the winter stands. For the same reason, the cost analysis revealed that only at the summer stand the LED interlighting was profitable. At that time, the total net income was positive and the benefit cost ratio favorable (1.15).