Growth and physiological responses of cherry tomato seedlings under nitrate stress

The effects of nitrate(NO3-)stress with 0,50,100,150,200mmol·L-1 concentrations were studied on growth and physiological and biochemical indexes of cherry tomato(Lycopersicon esculentum Mill.var.cerasiforme Alef.)variety ‘Dahong cherry tomato'using the hydroponic culture test.The results showed that the plant height,fresh weight,dry weight and relative water content decreased with the increasing of nitrate concentration after treated for 6days,while the root to shoot ratio increased first and then decreased.The contents of TBARS,ROS,H2O2and protein carbonyl(PC)of tomato seedlings increased with the increasing of nitrate concentration.The activities and gene expression of SOD,POD,CAT and APX of tomato seedlings decreased with the increasing of nitrate concentration.The contents of proline,soluble sugar and soluble protein of tomato seedlings increased with the increasing of nitrate concentration.Our experiment indicated that the 50mmol·L-1 NO3-had little effect on the plants,while 100 mmol·L-1 NO3-inhibited the growth of tomato seedlings,caused damage to the membrane lipid and decreased the activities of antioxidant enzymes(SOD,POD,CAT and APX);However,the increased osmotic adjustment substance could adjust themselves to avoid nitrate stress,which led to some tolerant ability of tomato to nitrate stress.