Effects of light quality on plant development and fruit metabolism and their regulation by plant growth regulators in tomato

Irradiation with artificial lighting in greenhouses and plant factories is mainly used to promote photosynthesis in tomato cultivation. In addition to photosynthesis, the light effects on morphology, flowering, and metabolism are also crucial as plant responses. Light period and quality have been studied for a long time in relation to the flowering of cut-flowers, strawberries, and many leafy vegetables. Light quality, such as red, far-red, and blue, should be considered with their photoreceptors containing phytochrome, cryptochrome, and flavin-binding kelch repeat, F-box 1. Light quality may also affect plant morphogenesis and the accumulation of valuable metabolites, and plant growth regulators (PGRs) are understandably related to them. However, the effects of PGRs, light quality, and photoreceptors on morphogenesis and metabolite accumulation have been only reported individually and have not been comprehensively discussed. In this review, the information on tomatoes, which are important both industrially and academically, was mainly summarized and discussed. Effects of light quality on plant growth, fruit ripening and metabolite accumulation, and biotic and abiotic stresses, as well as the involvement of gibberellin, auxin, ethylene, abscisic acid, jasmonic acid, and salicylic acid, are discussed here with the roles of the photoreceptors of each light quality and light signal integrators. There is no safety problem for light quality use with appropriate wavelength and intensity, and it is environmentally friendly to use light-emitting diodes as an energy-saving light source. Therefore, once their effect is clear with scientific evidence in relation to PGRs, light quality control technology can be used and contribute to the improvement of production and quality of tomatoes with the usage of PGRs.