Comprehensive insights into the influence of supplemental green light on the photosynthesis of ginger (Zingiber officinale Roscoe)

Although green light is not considered to contribute to the photosynthesis of plants, the photosynthesis of ginger, a dual-purpose vegetable used as a medicine and food, is affected by the green wave band. In this study, the supplementary green band of sunlight (SG) increased the net photosynthetic rate (Pn), maximal photochemical efficiency of PSII (Fv/Fm), and actual photochemical efficiency of PSII (Y(II)) compared with the sunlight treatment (S). The Pn and Fv/Fm of the SG treatment were higher than those of the white light (W) treatment, while the Pn and Fv/Fm of the green light (G) treatment alone were lower than those of the W treatment. Further analysis found that the minimal fluorescence (Fo) of the S treatment increased, especially at noon, while the Fo of the SG treatment decreased. Similarly, the Fo of the W treatment increased significantly, while the Fo of the white–green mixed light (WG) treatment decreased. The relative fluorescence values of the K-J-I bands in the SG and WG treatments were lower than those in the S and W treatments, respectively. The photochemical quenching (qP) of the WG treatment was higher than that of the W treatment, while the primary thermal losses corresponded to the sum of nonregulated heat dissipation and fluorescence emission (Y(NO)) of the WG treatment was lower than that of the W treatment. The SG treatment reduced the accumulation of plastoglobules but increased the accumulation of starch granules and leaf thickness. Moreover, the green band supplemented with white light significantly increased the biomass of the aboveground plant parts and promoted the active growth of the aboveground parts. Supplementing green light plays a regulatory role in ginger based on the following four points. First, it effectively promotes the transfer of electrons between the acceptor side of photosystem II; second, it optimizes ginger photosynthesis; third, it alleviates strong light stress by reducing the accumulation of reactive oxygen species; and fourth, it promotes heat dissipation and reduces the rapid burst of active oxygen in the chloroplast caused by excess energy. In summary, green light can significantly optimize the photosynthetic characteristics of ginger.