A century of soybean breeding increased photosynthetic capacity but not NPQ relaxation.

In a historical panel of 24 soybean genotypes, more than a century of breeding increased photosynthetic capacity but did not consistently improve NPQ relaxation, except AqE during reproduction.

• Why it matters: Breeding may have raised carbon assimilation, but it is unclear whether conventional selection also improved rapid photoprotective recovery needed to match high photosynthetic rates.
• What they did: The study measured NPQ relaxation, gas exchange, xanthophyll-cycle pigments, and expression of VDE, PsbS, and ZEP across vegetative and reproductive stages, alongside seed number and seed weight.
• The result: NPQ relaxation parameters were not linked to release year or seed traits at either stage, while AqE amplitude was negatively correlated with seed number and seed weight during reproduction; release year was positively associated with Amax, Vcmax, Jmax, seed number, and seed weight.

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