Articles
Effect of ultraviolet and far-red LED light added to broad spectrum white LED on lettuce production in vertical farm
Article number
1382_13
Pages
101 – 108
Language
English
Abstract
The use of light emitting diodes (LED) as an artificial light source on vertical farms is justified by their improved cost efficiency, heat dissipation and lifetime compared to high pressure sodium (HPS) lamps.
LED have been widely used as potential light sources in leafy green production as well as for the promotion of quantity and quality.
While in the past LED-based light sources were built from monochromatic, usually red and blue LEDs, in recent years the use of broad-spectrum white LEDs (WL) has become increasingly popular in plant cultivation with artificial lighting.
The proportion of secondary metabolic products produced in food crops increases under stress, resulting in a higher antioxidant content and healthier food.
Such stress can also be caused by excessive ultraviolet-A (UV-A) radiation, which can also be produced artificially with an LED light source.
By supplementing the wide-spectrum white LED light source with a far-red (FR) spectrum, the mass of biomass can be increased, and by supplementing with UV-A, the harmful nitrate content of lettuce can be reduced.
The aim of this study was to investigate the effect of broad-spectrum white LED light source supplemented with UV-A or FR spectrum LEDs in a vertical farm.
In this experiment, lettuce was irradiated with a WL for 12 h per day, supplemented with a combination of UV-A and FR, compared to the popular red-blue (RB) LED light source.
The four different light source resulted significant differences among SPAD values of leaves.
The white LED resulted the highest, while WL+FR and WL+UV resulted significantly lower SPAD value.
Also, the biomass result of lighting with WL was the highest, but not significantly different from the WL+FR and BR treatments.
The WL+UV-A treatment caused greater than 50% decrease in plant weight.
Significant differences were observed in the reflectance of the leaves in the near-infrared (NIR) spectra (740-1075 nm). In summary, lettuce was more sensitive to the addition of UV-A light compared to FR; however, the addition of UV-A to WL reduced yields significantly.
LED have been widely used as potential light sources in leafy green production as well as for the promotion of quantity and quality.
While in the past LED-based light sources were built from monochromatic, usually red and blue LEDs, in recent years the use of broad-spectrum white LEDs (WL) has become increasingly popular in plant cultivation with artificial lighting.
The proportion of secondary metabolic products produced in food crops increases under stress, resulting in a higher antioxidant content and healthier food.
Such stress can also be caused by excessive ultraviolet-A (UV-A) radiation, which can also be produced artificially with an LED light source.
By supplementing the wide-spectrum white LED light source with a far-red (FR) spectrum, the mass of biomass can be increased, and by supplementing with UV-A, the harmful nitrate content of lettuce can be reduced.
The aim of this study was to investigate the effect of broad-spectrum white LED light source supplemented with UV-A or FR spectrum LEDs in a vertical farm.
In this experiment, lettuce was irradiated with a WL for 12 h per day, supplemented with a combination of UV-A and FR, compared to the popular red-blue (RB) LED light source.
The four different light source resulted significant differences among SPAD values of leaves.
The white LED resulted the highest, while WL+FR and WL+UV resulted significantly lower SPAD value.
Also, the biomass result of lighting with WL was the highest, but not significantly different from the WL+FR and BR treatments.
The WL+UV-A treatment caused greater than 50% decrease in plant weight.
Significant differences were observed in the reflectance of the leaves in the near-infrared (NIR) spectra (740-1075 nm). In summary, lettuce was more sensitive to the addition of UV-A light compared to FR; however, the addition of UV-A to WL reduced yields significantly.
Authors
Z. Pék, L. Helyes, B. Balázs, S. Takács
Keywords
lettuce, vertical farm, LED, ultraviolet, far-red
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