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Light-emitting diode (LED) lamps signify one of themost 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 (PPF) intensity (mmol·m·s). 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 PPF 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. Fluorescent lamps are widely used in horticulture, particularly in in vitro culture. However, LED lighting systems have several beneficial properties, including their spectral composition, durability, long operating lifetime, wavelength specificity, relatively cool emitting surface, and high EE. Therefore, LED lighting is both energy efficient and beneficial to plants (Li et al., 2013; Massa et al., 2008; Ouzounis et al., 2015; Urrestarazu, 2013). Morrow (2008) suggests that solid-state lighting LED is one of the leading advancements in horticultural lighting in the last decade. Light intensity is one of the most important environmental factors for plant growth (Naoya et al., 2008). In contrast with highintensity light, low-intensity light is frequently reported as a factor for photoinhibition (Long et al., 1994). In addition, the effect of low light levels on plant growth and photomorphogenesis is well known; for example, they can lead to increased specific leaf area (SLA) and plant height (Fan et al., 2013; Steinger et al., 2003). In PPF, blue and red light have 90% absorption, and green light has 70 to 80% absorption (Terashima et al., 2009). The proportions of both red and blue light PPF have been studied by several authors (Li et al., 2013). Johkan et al. (2012) suggest that high-intensity green LED light promotes lettuce growth, and in particular, shortwavelength green light (510 nm) is available for active plant growth. On the other hand, the use of illuminance, a measure of radiation expressed as the PPF intensity from 380 to 780 nm [the photosynthetic radiation spectrum (PAR)], is often used in horticulture for determining the sufficiency of light intensity for proper plant cultivation. Multiple studies have been conducted with blue and red light (e.g., Fan et al., 2013), with different combinations of them (e.g., Li et al., 2013) and with the addition of a very specific section of the green spectrum (Johkan et al., 2012). Little information on continuous-spectrum LED lamps fit to a theoretical model of the maximum photosynthetic response has been recorded since McCree’s (1972) experiments on cultivated plants. The objective of this study was to evaluate the agronomy and EE of LED lamps manufactured for horticultural usewith a continuous spectrum fit to the maximum photosynthetic response vs. conventional white lighting at two different light intensities. Materials and Methods Plant material and growth conditions. The experiment was carried out at the University of Almeria (Spain) in an 1800 mm wide · 800 mm deep · 2200 mm high growth chamber. The light racks were spaced 50 cm apart, and the plants were exposed to a 16/8 h photoperiod (day/night) at a temperature of 28 to 18 C (day/night) and 85% to 80% relative humidity. Lettuce [cv. Astorga (Lettuce 1) and cv. Cervantes (Lettuce 2)], tomato (cv. Simona), and pepper (cv. Dulce italiano) plants with six true leaves were transplanted to a 0.750-mL pot containing coir substrate. The physical characteristics of the coir substrate have been previously described by Morales and Urrestarazu (2014). The fertigation was replenished if 10% of the readily available water was consumed (Rodrı́guez et al., 2014; Urrestarazu, 2004). The nutrient solution used was similar to that recommended by Sonneveld and Straver (1994). Five plants per species and five cultivars per replicate were considered after 35 d of treatment. The total LA was determined using the AM350 portable LA meter (ADC BioScientific Ltd., Hertfordshire, United Kingdom). The plants were separated into leaves, stems, and roots, immediately weighed to determine their fresh weight, dried at 75 C for 48 h, and reweighed. The SLAof each young plant wasmeasured using the following equation:

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