*2.7. Hydrogen Peroxide (H2O2) Measurement*

H2O2 was quantified via a colorimetric method [34]. Briefly, a 300 mg sample of frozen and ground tissue per tomato was extracted in a solution containing of 0.75 mL 0.1% (*w*/*v*) trichloroacetic acid (TCA), 0.75 mL 10 mM phosphate buffer (pH 7) and 1.5 mL 1 M KI. The homogenate was centrifuged (15,000× *g*, 4 ◦C, 15 min) and the supernatant transferred to a new tube and allowed to sit at RT for 20 min before obtaining the absorbance at 390 nm using a Varian CARY 4000 spectrophotometer (Agilent, Santa Clara, CA, USA). Measured absorbances were converted into H2O2 concentrations using a calibration curve constructed with a commercial H2O2 solution (Sigma Aldrich, St. Louis, MO, USA).
