Spectral light quality differentially modulates PSII energy partitioning among soybean genotypes

Cultivated soybean is a globally important crop; understanding its responses to different light spectra within the canopy is essential, especially considering the limited agricultural area. Energy flux and spectral quality are key components of the light environment that determine photosynthesis and, consequently, plant growth. These factors influence the composition and structure of photosystem II, thereby affecting energy partitioning between photochemical and nonphotochemical processes. This study evaluated the photosynthetic performance of two soybean genotypes under four light environments with distinct spectral compositions but equal energy flux. Results showed that PSII efficiency improved by the wavelengths outside the PAR range, irrespective of genotype. However, quantum yield parameters revealed genotype-specific responses under blue and red light. Plants exposed exclusively to red light exhibited reduced photosynthetic efficiency and increased photodamage after prolonged exposure, consistent with red light syndrome.