Accelerating soybean (Glycine max) leaf growth and stem strength by using natural daylight parameter characteristics

The ratios of red light (R)/blue light (B) and R/far-red light (Fr) stay relatively constant, which is the unique properties of sunlight. It may be a new way to optimise plant development in artificial lighting conditions. We assayed the potential effects of white light (W), 50% R 50% B (RB), and the unique properties of sunlight (N, R/Fr = 1.4, R/Fr = 1.1) under 500 μmol m−2 s−1 on soybean (Glycine max) plant growth. Our results showed that total leaf dry weight under N rapidly increased compared with the W and RB treatments from 30 days to 60 days. Soybean plants under N treatment had higher Rubisco activity and chlorophyll content than the W treatment at 50 days. Stem and petiole dry weight under N treatment grew by 454.3% from 30 days to 60 days. Compared with W and RB treatments, lignin content in the stems was also 26.9% and 34.5% higher at 50 days under N treatment, respectively. N treatment caused 22.9% and 26.2% higher cellulose content than the W and RB treatments at 50 days, respectively. N treatment led to 10.5% higher 13C assimilation than the RB treatment in stems. The spectral combination of sunlight enhanced soybean plant growth and stem strength in artificial light environment.