Two experiments were conducted in nutrient solutions, in a greenhouse, during the period of October/1982 to February/1983, in the Experimental Station of Campinas, Instituto Agronômico, State of São Paulo, Brazil. The objective was to study the differences among thirty nine corn (Zea mays L.) inbred lines in relation to N uptake and use under low N conditions. At first, five corn inbred lines were grown in 2,8 liter pots with different N levels in the nutrient solutions: 30, 60, 120, 180 and 240 N/liter. In a second trial thirty nine inbred lines were tested in nutrient solutions with 120mg N/liter, in the same growth system and similar growth conditions. The solutions were continuously aerated and the initial pH was 5.0. The pH was readjusted periodically throughout the experiments. The plants were allowed to grow without N reposition up to 30 days of age, when N deficiency symptoms appeared in the leaeves. Differences among lines were observed for top and root dry matter yields, for N concentrations, N contents, and efficiency ratios (dry matter produced per unit N absorbed). The N contents and the effìciency ratios averages followed, proportionally, lhe variation observed for dry matter yields, with correlation coefficients (r) of 0.87 and 0.92, and coefficients of variation of means (CV) of 8.7 and 16.1%, respectivelly. This indicated that both processes, absorption and use, varied among genotypes, but the mechanism of N use, appeared to be the main cause for the differential growth of the genotypes. The inbred lines were ranked and classified based on the plant dry matter data.
nitrogen; corn; efficiency; N uptake; N use; nutrient solution; plant selection