Response of growth, yield, and quality of pea shoots to supplemental light-emitting diode lighting during winter greenhouse production

Abstract

Low natural light levels during the winter months are a major limiting factor for greenhouse production in northern regions. To determine the effects of supplemental lighting (SL) on winter greenhouse production of pea shoots, crop growth, yield, and quality were investigated under the treatments of supplemental photosynthetic photon flux density (PPFD) of 50, 80, 110, and 140 μmol m−2 s−1, all with a 16 h photoperiod, plus a no-SL control treatment, inside a Canadian greenhouse from December to March. Light-emitting diodes with a red to blue PPFD ratio of 4:1 and peak wavelengths at 665 and 440 nm were used for the lighting treatment. During the trial period, the average natural daily light integral (DLI) inside the greenhouse was 5.3 mol m−2 d−1 and the average daily temperature was around 13 °C. Compared with the no-SL control, SL of 50–140 μmol m−2 s−1 increased stem length and leaf number before the first harvest and promoted the cumulative yield (kg m−2) of pea shoots throughout the five harvest times. The total yield (kg m−2) of five harvests and weekly average stem extension rate were proportional to supplemental PPFD within the range of 0–140 μmol m−2 s−1; however, SL of 50–80 μmol m−2 s−1, corresponding to total (natural + supplemental) DLI of 8.1–9.8 mol m−2 d−1, resulted in the best integrated quality based on the evaluation of individual fresh mass, soluble solids content, succulence, and firmness. Therefore, a total DLI ranging between 8.1 and 9.8 mol m−2 d−1 can be suggested as a target for winter greenhouse production of pea shoots under conditions similar to this trial.