Effect of the Spectral Quality and Intensity of Light-emitting Diodes on Several Horticultural Crops

Abstract

<jats:p>Light-emitting diode (LED) lamps signify one of the most important advances in artificial lighting for horticulture over the last few decades. The objective of this study was to compare the cultivation of four horticultural plants using a conventional white LED tube (T0) light against one with a good spectral fit to the maximum photosynthetic response (T1) at two intensities. The experiment was carried out with two types of young lettuce, tomato, and bell pepper plants. In a controlled environment chamber, six and four lamps per square meter were used to achieve high (H) and low (L) intensity, respectively. We measured the lighting parameters illuminance (lux) and photosynthetic photon flux (<jats:italic>PPF</jats:italic>) intensity (µmol·m<jats:sup>−2</jats:sup>·s<jats:sup>−1</jats:sup>). The dry and fresh weight, leaf area (LA), and specific index were measured to gauge plant growth. The photosynthetic activity and energy efficiency (EE) were recorded for each species over 60 days of cultivation. The results clearly demonstrate that, compared with conventional LED lamps, the specific horticultural LED lamps with an improved light spectrum increased the EE of the evaluated vegetables by 26%. At both the studied light intensities, plant growth was clearly more closely linked to the spectral fit of the light to the maximum photosynthetic response recorded by McCree (1972) than to <jats:italic>PPF</jats:italic> or illuminance (lux). We therefore suggest that a specific, detailed spectral distribution study be conducted to predict the effect of the specific quantity and quality of light used in this study on a single parameter of plant growth.</jats:p>

Effect of the Intensity and Spectral Quality of LED Light on Yield and Nitrate Accumulation in Vegetables

“…In the case of plants cultivated with high light intensity in T1, an average increase of 20% was seen compared with those cultivated under T0, in which the fresh weight of radish increased by 45%. A change in spectrum and intensity was shown previously to improve the parameters of vegetative growth by Yang and Park (2015); by Samuolien_ e et al (2011) in radish; by Urrestarazu et al (2016) in lettuce, to-mato, and pepper; and by Burattini et al (2017) in spinach. T1 produced a significant increase in fresh weight that varied between 12% for lettuce and 45% for radish.…”

“…T1 produced a significant increase in fresh weight that varied between 12% for lettuce and 45% for radish. Working in similar conditions, Urrestarazu et al (2016) found that the vegetative growth doubles and, in some cases, can be greater than 200%, whereas Samuolien_ e et al (2011) achieved significant growth (90% more) in radish.…”

“…Each lamp was 120 cm in length. Spectral specifications, quantitative light values, photon flux density (measured in micromoles per square meter per second) and illuminance (measured in lux) are described in a previous study (Urrestarazu et al, 2016). Photoperiods were 16/8 h (day/night) at a temperature of 28 to 18°C (day/night) and relative humidity of 85% to 80%.…”

“…HPS light. A recent study reported that spectra of the same intensity increases the lycopene content in tomato (N ajera et al, 2018) or contributes to better growth in lettuce, pepper, and tomato plants (Urrestarazu et al, 2016) or pomegranate plants (Bantis et al, 2018). Therefore, the effect of T1 is very significant in decreasing .9 ** P value *** *** L and H represent 4 and 6 lamps/m 2 , respectively.…”

“…In recent years, effective techniques have been developed for the growth and morphological development of plants, especially those grown in a soilless system and in closed and controlled structures under LED lights (Johkan et al, 2012;Urrestarazu et al, 2016). This advance in agriculture can be beneficial for the reduction of nitrate levels in plants that accumulate the most and, above all, in plants that are most consumed in the world.…”