Exogenous Melatonin and CaCl2 Alleviate Cold-Induced Oxidative Stress and Photosynthetic Inhibition in Cucumber Seedlings

Melatonin (Mel) and CaCl 2 have been demonstrated to play significant roles in plant cold tolerance. However, studies on their mechanisms of action are relatively limited. In this study, the effects of Mel and CaCl 2 on the growth of cucumber seedlings under low-temperature stress (10 °C/6 °C, day/night) and the possible interplay between Mel and CaCl 2 in this process were investigated. The results indicated that Mel and CaCl 2 at different concentrations inhibited low-temperature-induced reactive-oxygen species burst and decreased lipid peroxidation levels when compared with low-temperature stress alone, with the most significant effects being observed in the treatment with 100 μM Mel and 10 mM CaCl 2 ( P