The study evaluated how light, vapor pressure deficit, and temperature affect carbon assimilation in four Brazilian Saccharum officinarum varieties over a 530‑day field trial, using diurnal measurements and statistical modeling. Polynomial and multiple linear regression models accurately predicted photosynthetic rates, identifying optimal conditions (PAR ~1800 µmol m⁻² s⁻¹, VPD 2.34 kPa, temperature ~32.5 °C) and explaining up to 60% of the variability.