Chromatic Effects of Supplemental Light on the Fruit Quality of Strawberries

Abstract

Supplemental light is widely applied in greenhouses to promote the production and flavor of strawberries in global markets. The present selections of colored lights are, however, quite empirical or qualitative, from the perspective of photometry or colorimetry, which lacks precision. The accurate control of chromatic parameters of supplemental light and their chromatic influences on fruit quality have been under-studied. In this study, color parameters including ten groups of correlated color temperatures (CCTs-2250 K, 2400 K, 2600 K, 2800 K, 3000 K, 3500 K, 4000 K, 4500 K, 5000 K, and 6000 K) and two groups of illuminances (600 lx and 1000 lx) of supplemental lights were precisely controlled using a digital color-coding method applied to LED supplemental lights, and the strawberry was irradiated with the LED supplemental light from December 2021 to March 2022 in facilities cultivation (greenhouse). Moreover, the irradiation time was 6 h per day (4:00 a.m.–7:00 a.m., 5:00 p.m.–8:00 p.m.). We systematically investigated the chromatic effects of supplemental light on five parameters of strawberries: plant height, single weight, fruit hardness, soluble solids, and titratable acids. The results showed that the supplemental light generally lowered the single weight by 14% and fruit hardness by 6%, and increased plant height by 21%, the contents of soluble solids by 7.4%, and titratable acids by 27%. The chromatic dependences of the five parameters were different and might be strengthened, weakened, or shifted by light illuminance. Our results demonstrated the beneficial roles of supplemental light in accelerating maturation and enhancing the flavor of strawberries in greenhouse cultivation. These results provided valuable guidance for the effective cultivation of strawberries. Moreover, the controlling method for accurate colors was ready for the implementation of supplemental lights in other fruits or plants.