|Budget Amount *help
¥2,600,000 (Direct Cost : ¥2,600,000)
Fiscal Year 1993 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1992 : ¥1,300,000 (Direct Cost : ¥1,300,000)
Fiscal Year 1991 : ¥800,000 (Direct Cost : ¥800,000)
Breeding of crops with efficient use of plant nutrient is one of the goals for low-input crop production. In this study, two kinetic parameters, Km and Vmax, for high affinity nitrate uptake by young seedlings were determined in several crop plants for evaluating the expression of nitrate uptake gene (s). Summary of the results are shown as follows.
1) In twenty Japanese barley cultivars, Km and Vmax were 50.9-111.7 mu M and 2.24-4.99 mu mol/g/h, respectively. IIowever, these results were thought to be underestimated because of experimental procedure. 2) In barley genotypes with different water tolerance at seedling stage, Km and Vmax were 143.0-209.4 mu M and 3.37-7.85 mu mol/g/h, respectively. No relationships between the kinetic parameters and water tolerance was observed. 3) In sixteen rice cultivars including both indica and japonica, Km and Vmax were 75.7-130.3 mu M and 4.30-7.17 mu mol/g/h, respectively. In the cultivars of indica and japonica showing similar level of Km, indica cultivars tended to show lower Vmax than japonica cultivars. 4) Km and Vmax in several genotypes of wheat, rye and Triticale were similar level of those of barley and rice. 5) In four rice mutants affecting nitrate assimilation, M605, a chlorate hypersensitive mutant, showed significantly higher Km than that of the wild type, Norin 8. Furthermore, there was difference in ratio of nitrate uptake ability from 40 mu M KNO_3 to that from 400 mu M KNO_3 in 145 rice genotypes, suggesting variability in the kinetic parameters.