Far-red light enhances mesophyll conductance and photosynthesis in tomato on short timescale below sunlight far-red fraction only.

Far-red light at levels found in direct sunlight enhances mesophyll conductance and photosynthesis in tomato leaves, but further increases do not produce additional effects.

• Why it matters: Understanding how different fractions of far-red light influence photosynthesis can improve crop productivity and light management strategies, especially under natural sunlight conditions.
• What they did: Researchers exposed tomato leaves to varying R:FR ratios (10.5, 1.1, and 0.48) under controlled light regimes, measuring gas exchange and carbon isotope ratios to assess changes in mesophyll conductance, stomatal conductance, and CO2 assimilation.
• The result: Increasing FR from low levels to those in direct sunlight boosted both mesophyll conductance and net CO2 assimilation, but further FR increases did not enhance these parameters, suggesting a saturation point for short-term photosynthetic response.