The investigation of the alleviated effect of copper toxicity by exogenous nitric oxide in tomato plants

As a bioactive signal, nitric oxide (NO) is involved in multiple plant physiological responses, especially under some abiotic stress. Here, we investigated the effects of exogenous nitric oxide on both the reactive oxygen species (ROS) scavenging metabolism and regulating functions of plasma membrane and tonoplast in tomato plants treated with 50 mu M CuCl2. Copper stress induced significant accumulation of H2O2, led to serious lipid peroxidation, and finally markedly decreased shoot height and fresh weight of tomato plants. The application of 100 mu M sodium nitroprusside (SNP - NO donor) promoted some antioxidant enzymes, reduced accumulation of H2O2, and adjusted the activity of H+- ATPase and H+- PPase in plasma membrane or tonoplast, and significantly alleviated the growth inhibition induced by copper toxicity. On the other hand, the application of sodium ferrocyanide (an analog of SNP) and sodium nitrate or nitrite (the decomposition product of NO or its donor SNP) which did not release NO, did not show the effects of SNP. Furthermore, the effects of SNP were reverted by addition of hemoglobin (an NO scavenger). Therefore, these results indicated that exogenous NO could effectively assuage copper toxicity by physiological and biochemical response so as to maintain normal growth.