Abstract
The effect of multicolor pulsed light-emitting diode (LED) irradiation on lettuce “Defender” growth, photosynthetic performance and antioxidant properties was studied. The experiments were designed to compare the continuous and pulsed lighting (0.5, 1 kHz; 50% duty ratio) effects of B450, G520, R660 and FR735 lighting components, maintaining total diurnal integral light quantity (DLI 14.4 mol m−2 day−1) constant during the 16-h photoperiod. The results showed that lettuce grown under pulsed irradiation displayed superior growth performance, including a significant enhancement of fresh (~32%) and dry biomass (~36%) and leaf area (~48%). Lettuce cultivated in both pulsed light treatments was characterized by the higher photosynthetic rate, chlorophyll (a,b) and carotenoid concentration. However, the total phenol and antioxidant properties in lettuce were more dependent on the specific pulsed light frequency. Only treatment with 1 kHz frequency was effective for higher phenol content, 2,20-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) free radical scavenging activity and Fe2+ reducing antioxidant power (FRAP). Thus, our results propose the role of pulsed LED light in improving the photosynthetic efficiency and antioxidative properties of lettuce plants cultivated indoors. In the future, pulsed lighting techniques should be included in the development of artificial lighting systems in controlled environment agriculture (CEA) to produce high-quality crops with the possibility to save electricity.
Highlights
Light is a crucial factor in the life cycle of plants and its quality and quantity, as well as the photoperiod, have significant effects on plant growth, development and metabolism
Manipulation of light for plant cultivation is an important issue that is studied in controlled environment agriculture (CEA), where several different artificial lighting conditions are commonly used in plant factories, growth chambers and greenhouses
Our experiments and research results show that pulsed Light-emitting diode (LED) lighting significantly promotes plant growth in terms of leaf area and fresh and dry weight
Summary
Light is a crucial factor in the life cycle of plants and its quality and quantity, as well as the photoperiod, have significant effects on plant growth, development and metabolism. Manipulation of light for plant cultivation is an important issue that is studied in controlled environment agriculture (CEA), where several different artificial lighting conditions are commonly used in plant factories, growth chambers and greenhouses. Light-emitting diode (LED)-based horticultural lighting systems have increasingly been used in CEA to research the physiological responses of plants to light as well as for commercial production of horticultural crops [1]. Blue and red LED light combinations are most commonly used, as these wavelengths are predominantly absorbed by photosynthetic pigments and are sufficiently effective for plant growth and photosynthesis of various crops [6,7,8]. In closed CEA systems, where artificial lighting is the only source of light, the lighting strategies have changed from simple red and blue combinations to a multicomponent lighting spectrum, mimicking the wide spectrum of the sun
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