The chlorophyll fluorescence induction kinetics or Kautsky effect, in dark‑adapted leaves upon a sudden irradiation, was detected in 1931 by Hans Kautsky. Measurements of chlorophyll fluorescence in vivo were made to responses and degrees of salt stress in leaves of three citrus rootstocks without grafting and their combinations. Citrus macrophylla Wester' (Mc), 'Cleopatra mandarin' (Cl) and 'Carrizo citrange' (Cz) and the combinations: Cl/Mc, Cz/Mc, Mc/Cl, Cz/Cl, Mc/Cz, and Cl/Cz. They were grown in three differents sodium chloride levels in the nutrient solutions: T₀ (0 mmol/L), T₁ (25  mmol/L) and T₂ (50 mmol/L). The chlorophyll fluorescence parameter measured decreased when the sodium chloride level increased.