Effects of Melatonin Treated Radish on the Growth of Following Stubble Lettuce under Salt Stress

The effects of melatonin (MT) treated the previous stubble radish seedlings on the growth of following stubble lettuce seedlings under salt stress were studied by pot experiment. The results showed that MT increased the biomass, root volume, root length, plant height, chlorophyll content and carotenoid content of following stubble lettuce, but the effect was not significant. When the does of MT was 50 mu mol/L, these indexes got the maximums. With the increase of MT concentrations, the activities of SOD and CAT reduced, but the activity of POD improved first and then reduced. The maximum of POD activity was at 50 mu mol/L of MT, which improved by 16.48% compared with the control. MT significantly increased the soluble protein content of following stubble lettuce compared with the control, and the maximum was at the concentration of 50 mu mol/L of MT. Therefore, only 50 mu mol/L of MT treated the previous stubble radish could promote the growth of following stubble lettuce under salt stress.