Identification of genotypic differences in micronutrient concentrations of staple food crops is essential if plant breeding strategies are to improve human mineral nutrition. The concentrations of zinc (Zn), iron (Fe), copper (Cu), and manganese (Mn) in polished grains of 285 rice (Oryza sativa L.) genotypes and the relationship between concentrations of the four micronutrient elements and concentrations of protein and lysine were examined. Significant differences (P<.01) were found in the concentrations of Zn, Fe, Cu, and Mn in polished rice with a fairly normal distribution among rice genotypes. On average, Cu and Zn concentrations of Indica rice were about 2-fold higher than Japonica rice, while Fe concentrations of Japonica rice were slightly higher than Indica rice. Among Indica rice genotypes, red rice contained 1453
Salinity is one of the most important factors affecting the nitrogen-removal efficiency of denitrifying bacteria. A series of different ion combinations and salinity gradients were carried out to clarify the effects of ion types and concentrations on nitrogen removal by halophilic aerobic denitrifying bacteria RAD-2. Nitrate concentrations, nitrite concentrations, TAN concentrations, and OD600 were monitored to investigate their effects on denitrification in each group. The results showed that Na+, K+, and Cl- accelerated the denitrification process and improved nitrogen-removal efficiency at moderate additions, while Ca2+ and Mg2+ showed no significant effect. Na+ was effective alone, while K+ or Cl- needed to be combined with at least one of Na+, K+, or Cl- to achieve similar efficiency. The batch tests of salinity confirmed that the addition of a moderate concentration of NaCl/Na2SO4 could effectively improve nitrogen-removal efficiency, while excessive salinity might hinder denitrification metabolism. In the salinity range of 5~40‰, a 5‰ dosage might be the most economical method for strain RAD-2. Real-time PCR experiments on 17 key nitrogen metabolism-related genes revealed that chloride was widely involved in the nitrogen and carbon metabolism of microorganisms by altering cell osmotic pressure and opening ion channel proteins, thereby affecting the efficiency of denitrification. The results of this study may contribute to a better understanding of the different roles of various ions in aerobic denitrification and highlight the importance of salinity control in highly salted wastewater treatment.
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