The response and tolerance mechanisms of lettuce (Lactuca sativa L.) exposed to nickel in a spiked soil system

Nickel contamination may lead to the destruction of food, ecological safety and its toxicity to plants remains to be studied in depth. In our present study, the translocation factors (TFsoil to root and TFroot to shoot) revealed a significant logarithmic decline with the increase of Ni exposure. In lettuce roots, NiHAC played an important protective role against high Ni stress and the ratio of Ni with high activity (NiE and NiW) in root decreased with the addition of Ni. The activities of antioxidant enzymes (CAT, POD and SOD) in the lettuce roots were increased and might be the way for lettuce to adapt Ni stress. CAT and POD can be great indicators of Ni pollution exhibiting better dose-effect relationships with Ni. Under high Ni stress, lettuce roots contained higher levels of MDA suffering greater pressure than shoots. Expression levels of gene GST 23-like indicated a remarkable (P < 0.05) down-regulation and then this trend would be alleviated after high Ni exposure, and it was positively correlated with GST concentrations (R2 = 0.704). We believe that our research would open up the new avenues for effective understanding ecological risks of Ni.