The Selection Of Low-Nitrogen-tolerant Variant In Maize

Nitrogen is one of the important elements to the growth of maize. In our country the nitrogen content descended quickly with the yield increasing. The lower content of nitrogen has different some influence on the growth and yield of maize. There was only 0.02%-0.2% content of nitrogen in soil, and only 30%-40% utilizing rate in the present season of nitrogenous fertilizer. So it is practical significance for barren area to select and breed new nitrogen-tolerant varieties about germ plasm of maize. The calli were induced from the immature embryos of maize in our lab, screening was carried out by somatic cell culture.Calli were induced with immature embryos of maize. the calli were continually selected in N6 medium with lowering nitrogen concentrate four times, the tolerant calli were maintained on natural medium for restoration culture three times, the variant of tolerant calli were obtained. R(?) plants were regeneration from tolerant calli variant, cultivated several days in greenhouse, then transplanted to field. R₁ seeds were obtained by self-pollination.Two kind of screening measures were adopted in somatic cell selection: equal concentration and gradient selection. In the procedure of somatic cell selection the growth amount of callus was determined and the type of callus was observed among selection. The 1000-kernel weight and the quality of R₁, the nitrate reductase and glutamine synthetase activity of R₁ young seedling were determined. The experimental results showed that the growth amount and quality of callus descended with the concentration of nitrogen reducing. With the nitrogen concentration decreasing, type II calli decreased, type III calli increased. The lower was the concentration, the slower was the growth. According to the comparison with the influence on calli between N, T and X series concentration, we thought that reducing...