Effect of Caffeic Acid on Growth and Reducing the Destructive Effects of Salinity on Greenhouse Cucumber (Cucumis sativus var. Super daminos)

To investigate the effect of different levels of salinity and caffeic acid on growth and physiological characteristics of cucumber (Cucumis sativus var. Super daminos), a factorial experiment was conducted in a completely randomized design with salinity treatments 0, 50, 100, 150 mM NaCl and caffeic acid 2, 4 and 6 mg / L with three replications in research greenhouse of Isfahan University of Technology. The results showed that shoot dry weight at a concentration of 6 mg/L reduced. In all salinity levels, treatments lacking caffeic acid showed the lowest amount of photosynthesis that the lowest amount observed in 50 mM NaCl × 4 mg/L caffeic acid treatment. Relative water content in lacking saline treatments decreased significantly with increasing caffeic acid concentration, but at the highest salinity level, 4 mg/L caffeic acid application increased the relative water content. Caffeic acid application increased salinity levels of 100 and 150 mg/L and increased antioxidant activity than control so that the highest amount was observed in 150 mM NaCl × 2 mg/L caffeic acid (0.27 %) and 100 mM NaCl × 6 mg/L caffeic acid (0.25 %) treatments. It seems that caffeic acid at low concentrations improves the growth and physiological characteristics of cucumber, but has a toxic effect in high concentrations.