The Impact of a Six-Hour Light-Dark Cycle on Wheat Ear Emergence, Grain Yield, and Flour Quality in Future Plant-Growing Systems.

Cultivating wheat ( Triticum aestivum ) in a closed environment offers applications in both indoor farming and in outer-space farming. Tailoring the photoperiod holds potential to shorten the growth cycle, thereby increasing the annual number of cycles. As wheat is a long-day plant, a night shorter than a critical length is required to induce flowering. In growth chambers, experiments were conducted to examine the impact of a 6 h light-dark cycle on the timing of wheat ear emergence, grain yield, and flour quality. Under equal daily light-integral conditions, the 6 h light-dark cycle promoted growth and development, resulting in accelerated ear emergence when compared to a 12 h cycle, additionally indicating that 12 h of darkness was excessive. To further stimulate heading and increase yield, the 6 h cycle was changed at the onset of stem elongation to a 14 h-10 h, mimicking spring conditions, and maintained until maturity. This successful transition was then combined with two levels of light intensity and nutrient solution, which did not significantly impact yield, while tillering and grain ripening did increase under higher light intensities. Moreover, it enabled manipulation of the baking quality, although lower-end falling numbers were observed. In conclusion, combining a 6 h light-dark cycle until stem elongation with a 14 h-10 h cycle presents a promising strategy for increasing future wheat production in closed environments. The observation of low falling numbers underscores the importance of factoring in flour quality when designing the wheat-growing systems of the future.