ABSTRACT
To provide a theoretical reference to nitrogen fertilizer management for maize and eco-enviromental protection in the irrigated area of Ningxia, we established the critical nitrogen concentration (Nc) dilution curve of maize under drip-irrigated condition. The nitrogen nutrition index (NNI) was deduced from the established Nc curve model, to diagnose feasibility of nitrogen nutrition. Six levels of nitrogen application rates including 0, 90, 180, 270, 360 and 450 kg·hm-2 were conducted in field with maize variety 'Tianci 19'. During two-year field study, the Nc dilution curve and NNI model of maize were established based on leaf dry matter (LDM). The results showed that: 1) There was a negative power function relationship between LDM and Nc, which presented as two parts, if LDM<1.15 t·hm-2, Nc=3.2%, while if LDM≥1.15 t·hm-2, Nc=3.29LDM-0.29. 2) The root mean square error (RMSE) and standardized root mean square error (n-RMSE) of the model were 0.203 and 8.0%, respectively, with fine stability among years. 3) The NNI ranged from 0.47 to 1.44 with different nitrogen application rates. In addition, NNI was positively correlated with yield and negatively correlated with agronomic utilization efficiency of nitrogen fertilizer at different growth stages of maize. Therefore, NNI could be used to explain maize yield changes with and without nitrogen limit under drip-irrigated system. In conclusion, the critical nitrogen dilution curve established from leaf dry matter could be applied to accurately estimate nitrogen nutrition status throughout the whole growing stages from the jointing stage to silking stage of maize under drip irrigated system.
Subject(s)
Nitrogen , Zea mays , Biomass , Fertilizers , Plant LeavesABSTRACT
<p><b>OBJECTIVE</b>To study the effect of ozonized saline on the activation of the Keap1-Nrf2-ARE signaling pathway in rat liver cells.</p><p><b>METHODS</b>Twenty male Sprague-Dawley rats were randomly divided into ozonized saline (OS) group, model group, ozonized saline control (OSC) group and normal control (NC) group. The rats in OS group and model group were intravenously administered with OS or oxygen saline (5 ml/kg) respectively, once a day for 15 days, and then intraperitoneally injected with CCl4 dissolved in oliver oil. The rats in OSC group were pretreated with OS for 15 days. The rats in NC group were fed normally for 15 days. On the 16th day, the rats in OSC group and NC group were intraperitoneally injected with oliver oil (2 ml/kg) without CCl4. After 24 hours of CCl4 or olive oil intraperitoneal injection, the serum levels of alanine transaminase (ALT) and aspertate aminotransferase (AST) were measured. The liver tissues were also collected for detection of total anti-oxygen capability (TAOC), glutathione (GSH), catalase (CAT), Glutathione peroxidase (GPx). Western Blot was used to detect Nrf2 and immunofluorescence staining assay to display intracelluar distribution of Nrf2.</p><p><b>RESULTS</b>Compared with the rats in model group,the serum ALT and AST levels of rats in OS group were significantly lower (P < 0.01) ,which were (1240.4 ± 188.2) U/L and (1245.4 ± 176.9) U/L vs (539.8 ± 175.3) U/L and (546.0 ± 130.2) U/L, and the TAOC, CAT, GPx and GSH activity of rats in OS group were significantly higher, which were (0.72 ± 0.24) U/mg, (1.05 ± 0.21) mg/g, (676.9 ± 115.1) U/mg and (45.2 ± 14.3) U/mg vs (1.37 ± 0.19) U/mg, (2.23 ± 0.55) mg/g, (1024.6 ± 162.9) U/mg and (68.2 ± 9.9) U/mg, respectively. In contrast with NC group, pretreatment of OS in OSC group elevated TAOC, CAT, GPx and GSH activity (P < 0.01 or P < 0.05). Ozonized saline can strengthen the Nrf2 expression in liver cells.</p><p><b>CONCLUSION</b>Preconditioning injection of ozonized saline can reduce rat's liver injury induced by CCl4. The ozonized saline, as a novel Nrf2 activator, can reduce the oxidative damage of radical oxygen species (ROS) and the deleterious substance by activating the Keap1-Nrf2-ARE signaling pathway and its downstream genes expression.</p>
