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

Abstract

<jats:p>At present, trends exist in the production of food for the benefit of human health. The negative effect of an excessive intake of nitrates accumulated in vegetables is well known, causing worldwide concern. Light plays an important role in the accumulation of this ion. The objective of this work was to evaluate the effect of light-emitting diode (LED) spectra used in artificial lighting for horticulture on the accumulation of nitrates in leafy and root vegetables compared with the effects with white LED lights. Two independent experiments were carried out in the culture chamber. In Expt. 1, six species of nitrate accumulators were used: arugula, spinach, lettuce, endive, radish, and beetroot. In Expt. 2, four lettuce cultivars were used. In both experiments, the treatments were two spectra—T1 = AP67 Valoya<jats:sup>®</jats:sup> and the control (T0) = white Roblan<jats:sup>®</jats:sup>—at two illumination intensities [high (H) and low (L)] with a 16/8-hour (day/night) photoperiod. The fresh biomass and the concentration of nitrates were measured at 35 days of treatment posttransplantation. An important and significant increase of 50% of the mean fresh weight was obtained in all the species when the light intensity increased. Except for spinach in the low-intensity treatment, all nitrate content values were less than the maximum limits of European regulation. The nitrate content generally decreased with increasing intensity, and this benefit was greater in the T1 treatment. T0 showed a reduction in the nitrate content compared with T1 in only one case, which was the H in beetroot. A large and significant reduction was observed in the nitrate content in T1. For L in Expt. 1, the nitrate decrease was 18%, whereas for H, it was 35%. In Expt. 2, the decrease in the nitrate content was 10% for L and 21% for H. A greater benefit was derived when using the photosynthetic spectrum in the growing chambers under low light intensity.</jats:p>

Fertigation Temperature Adjustment Enhances the Yield and Quality of Saffron Grown in a Soilless Culture System

“…This was accomplished by placing the material in a convection oven (Heratherm; ThermoScientific, Waltham, MA) at 75 C until a constant weight was achieved. This was measured using an OHAUS Adventurer Analytical Precision Analytical Balance (model AX 124/E; OHAUS, Parsippany, NJ), with a precision to four-tenths of a gram (N ajera and Urrestarazu, 2019;Urrestarazu et al, 2016).…”

Optimization of Artificial Light for Spinach Growth in Plant Factory Based on Orthogonal Test

“…Under our experimental environment, in the preliminary experiments, when the light intensity was higher than 150 µmol•m −2 •s −1 , the spinach plant appeared burnt and died; when the lighting time exceeded 14 h per day, the plant showed early bolting. According to the preliminary experiments and the relevant researches before [16,17], the intensity of planting light for spinach growth should be set lower than 150 µmol•m −2 •s −1 , and the lighting time should not exceed 14 h/day. Thus, the experiment used the L 4 (2 3 ) orthogonal table [28] regardless of interaction to analyze.…”

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The Effect of Plant Growth Compensation by Adding Silicon-Containing Fertilizer under Light Stress Conditions

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