This work was carried out under greenhouse conditions during two successive seasons 2017 and 2018, at the Farm of
Faculty of Agriculture, Menoufiya University, Shibin El-Kom to study the effect of three antioxidants i.e; salicylic acid,
ascorbic acid and boric acid with two concentrations (15 and 30 mg/l) on tomato early blight disease incidence, disease
severity, some growth characters, water relations and chemical compositions of tomato plants. All treatments of
antioxidants significantly reduced disease incidence and disease severity, in as much as, increased significantly plant
height, leaf area fresh and dry weight, total water content (TWC), bound water, free water, relative water content (RWC)
and transpiration rate. Also, application of antioxidants increase in chlorophyll A, chlorophyll B, carotenoids, total
carbohydrates, total sugars, protein and prolien on tomato plants. Salicylic acid (30 mg/l) was the best treatment followed
by the (30 mgl/l) of ascorbic acid While, boric acid (15 mg/l) recorded the least effect on disease severity, disease
incidence, growth characters, water relations parameters and chemical compositions.