Faster and greater wheat production governed by LED light in controlled environment agriculture

Wheat (Triticum aestivum L.) is a major food crop grown worldwide. However, field-grown wheat is generally restricted to only one generation per year and has a fluctuating yield, which limits wheat improvement and will fail to meet future food demands. To minimize the generation time and increase total annual wheat production, five light regimens with varying day lengths and spectral distributions - 12 h light/12 h dark+white light (P12W), 17 h light/7 h dark+white light (P17W), 22 h light/2 h dark+white light (P22W), 22 h light/2 h dark+red:green:blue light at 6:3:2 (P22RGB), and 22 h light/2 h dark+red:blue light at 6:1 (P22RB) - were developed by adjusting the light-emitting diodes (LEDs) in a controlled environment. The results showed that controlled wheat cultivation under LED lighting with varying day lengths and spectral distributions can potentially provide “faster” and “greater” grain production. Prolonging the day length (from 12 to 17 h and then to 22 h) accelerated wheat development, particularly shortening the duration before flowering, and the longer the prolonged time, the earlier the flowering. However, a 22 h day length (e.g., the P22W treatment) affected plant morphological traits, reduced dry matter accumulation, and resulted in a loss of yield-related components due to increased stress and disrupted pollen development. Surprisingly, regulating the spectral distribution toward the red-light region under long-day conditions (e.g., the P22RB treatment) could partially restore the grain yield of wheat. The light regime with a rich red-light region contributed to greater dry matter accumulation, carbohydrate flow to reproductive tissues, and sporopollenin biosynthesis, resulting in improved plant morphology and grain yield. Collectively, the optimized light regimes represented by the P17W and P22RB treatments in controlled environment agriculture can produce 5–6 generations of wheat per year, yielding 3.16–5.87 kg m^–2 yr^–1, which is 3.59–6.68 times higher than field cultivation. Thus, using appropriate LED light regimens is a favorable way to achieve rapid generation cycling and high productivity in controlled wheat cultivation.