Amber LEDs outperform red, blue, and red-blue-amber LEDs for lettuce

Abstract

ABSTRACT Debate persists on light in controlled environment agriculture. To dissect the effects of conventionally used wavelengths on a crop and provide new information to this expanding food production sector, this study investigated the effects of monochromatic and combined red, blue, and amber light on lettuce growth with increasing light intensities (up to 1300 µmol·m−2·sec−1) for 18 days with a 16 h·d−1. Under amber light at PPFDs ranging from 500 to 700 µmol·m−2·sec−1, fresh mass displayed a 33.3% greater yield when compared to red light at the same PPFD. Suppressed growth was observed with either red or amber alone at high PPFD (>800 µmol·m−2·sec−1). Blue light was the least productive of the four treatments, yet lettuce plant growth was not suppressed at high intensities. No growth suppression was observed for lettuce plants grown under combined red-blue-amber light at high intensities, and these plants exhibited greater biomass yield than blue light alone. Varied degrees of pigmentation occurred under each light treatment, yet bleaching was only observed in plants grown under amber light alone at PPFD above 1000 µmol·m−2·sec−1. Findings present novel plant responses to high intensity light, setting precedence for future experiments aimed at expanding the use of LEDs in horticulture.