Effects of red and blue light intensities on the growth, yield, and quality of perennial ryegrass

Facility forage production is an effective approach for solving the problem of insufficient forage grass production capacity. In order to establish suitable light intensity for perennial ryegrass (Lolium perenne) production in plant factory with artificial light, we examined the effects of red and blue LED light intensities 150, 250, 350, 450, and 550 μmol·(m²·s)⁻¹ on the yield and the quality characteristics of the chlorophyll, soluble sugar and amino acid contents of perennial ryegrass. The results revealed that light intensity had a marked effect on yield, with increases in yield being recorded in response to an increase in light intensity. Light intensity was also found to influence the contents of chlorophyll b and total chlorophyll. At the second cutting, we detected significant positive correlations between light intensity and soluble sugar, amino acid, and cysteine contents, as well as DPPH free radical scavenging activity. At a light intensity of 450 μmol·(m²·s)⁻¹, we recorded 7.6 and 9.4 tillers per plant for the first and second cutting, soluble sugar contents were 13.29 and 8.85 mg·g⁻¹ and amino acid contents were 15.65 and 19.48 mg·g⁻¹, respectively, and the DPPH free radical clearance rate was 31.47% and 24.37%, respectively. On the basis of these findings, we established that high-quality ryegrass can be efficiently cultivated under red and blue LED light, with the optimal production conditions being a light intensity of 450 μmol·(m²·s)⁻¹ and red to blue ratio of 4:1.