Genotypic response and selection pressure on nitrogen-use efficiency in rice under different nitrogen regimes.
1995
Wu P. | Tao Q.N.
Eight rice genotypes including hybrid rice, semidwarf rice, and tall varieties were studied under greenhouse condition with three levels of nitrogen (N) applied at 0.50, 1.00, and 1.50 g N/plant. Grain dry weight, straw biomass (including root), grain, and straw N concentration (GN% and SN%) were measured at maturity. Harvest index (HI), physiological N-use efficiency (PE), defined as a ration of grain yield to total N absorbed (Nt), uptake efficiency (UE), defined as a ratio of Nt to applied nitrogen (Na), and agronormcal N-use efficiency as a product of PE and UE were calculated based on the measurements. Chlorophyll content (Chl), soluble protein (SP), and photosynthetic N use efficiency (CER/N) of flag and the last second leaves were also measured. There was a significant variation among genotypes, N rates, and the interaction between genotype and 29 rate for all measured parameters, except GN% among genotypes. Similar selection pressure on PE and UE as the components of AE was observed at low N rate. At moderate N rate, the selection appeared favorable to PE but to UE at high N rate. The effects of measured parameters on PE and UE were different at different N rates, which may explain the difference in selection pressure on PE and UE under different N conditions.
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