Screening For N Efficiency Rice And Research On The Mechanism Of N Efficiency

To get the different N efficiency rice varieties, 485 varieties were screened at soil cultural and solution conditions. 3 N levels (N₁ 0.075gN/kg Soil, N₂ 0.125 gN/kg Soil, N₃ 0.25 gN/kg Soil) were treated in the soil cultural experiments. To indentify the indicators evaluating N efficiency in rice, the ratios between N₁ and N₃ such as relative dry weight, relative SPAD, relative tillers, relative shoot height were investigated. The results showed: relative dry weight and relative SPAD changed from 0.13 —0.96, 0.35 — 0.93 respectely, so the differency in N efficiency could been indicated, relative tillers, relative shoot height were changed in varieties also,but the range were small. So the relative dry weight and relative SPAD were used to evaluate the N efficiency in rice , and 3 N efficiency varieties (4^#, 33^#, 65^#)and 3 N inefficieny varieties(41^#, 160^#, 169^#) were gotten.To identify the results screened in soil experiment, variety 4 and 160 were cultivated in nutrition solution at 2 N levels (40mg.L^-1, 7mg.L^-1). Results showed that N efficiency in variety 4^# was higher than that in variety 160^#.The mechanism for N efficiency was studied with variety 4^# and 160^#, the results showed that:in lower N level, varietiy 4^# had better root morphology; higher N content, higher affinity for ammonium-N, higher protein ,free ammonia acid content,less N-loss from plant.