H₂S Promotes Assimilation Of Nitrate Nitrogen Under Low-Nitrogen Condition In Wheat

Wheat is one of the most important grain crops in world. As an effective way of promoting wheat production, nitrogen fertilization also caused a series of environmental pollution especially when it was misused. People have been trying to find out the best amount of nitrogen for wheat growth in order to improve its nitrogen use efficiency. In terms of this, it will not only increase wheat yields and economic returns, but also reduce the use of nitrogen and thus save costs. H2S is thought as the third gaseous signaling molecule discovered after nitric oxide (NO) and carbon monoxide (CO), and its role has been widely studied in animals. Recently the physiological mechanisms of H2S in plants is becoming a hot topic. Here, the effect of exogenous H2S on nitrogen utilization efficiency in wheat was studied, which could provide new insights into nitrogen utilization efficiency.In this study the common wheat (Triticum aestivum cv Yangmai 16) was used. After treatments with five different concentrations (0,0.01,0.1,0.5,1 mmol·L-1) of NaHS (H2S donor) dissolved in Hogland nutrient solution, we found the optimum concentration of NaHS for the growth of wheat seedlings by assaying chlorophyll content, net photosynthetic rate (Pn) and dry weight. Then the effects of optimum NaHS on low (2 mmol·L-1), medium (7.5 mmol·L-1) and high (15 mmol·L-1) concentrations of nitrate nitrogen in Hogland nutrient solution culture were examined on the aspects of photosynthesis and nitrate nitrogen assimilation in wheat.The results indicated:(1) H2S was able to promote the absorption of nitrate nitrogen in wheat seedlings, and increase the biomass by 15.5%; (2) The soluble proteins, total nitrogen and chlorophyll contents in the leaves of wheat seedlings increased significantly; (3) After the treatment with NaHS, the activities of nitrate reductase (NR), glutamine synthetase (GS) and glutamate dehydrogenase (GDH) increased under low and medium concentrations of nitrate nitrogen culture, and increased significantly under low concentration of nitrate nitrogen culture; (4) Under high concentration of nitrate nitrogen culture, the activities of NR and GS reduced by 22% and 13% respectively compared with control, while the activity of GDH changed insignificantly in comparison with control. Above results suggest that H2S could promote the assimilation of nitrate nitrogen in wheat seedlings under low concentration of nitrate nitrogen culture.