PLANT NITROGEN DISTRIBUTION IN WHEAT CULTIVARS

Five wheat cultivars were examined for patterns of nitrogen uptake and distribution to the aboveground plant parts at 10 different stages throughout growth up to ripeness. Patterns in the proportionate allocation of total plant nitrogen in the mature plant of each cultivar were found to differ significantly. Significant differences existed between cultivars in the nitrogen percentages of culm, glume and rachis tissue in the mature plant. Translocation efficiency, expressed as the proportion of total plant nitrogen in the head, ranged from c. 36 to 60% in the cultivars, while the proportion of total grain to total plant nitrogen ranged from c. 25 to 52%. Within-head translocation efficiency, as total grain nitrogen to total head nitrogen, ranged from c. 75 to 94%. The cultivars Argentine IX and Petit Rojo possessed comparatively high values for all three translocation estimates. Their very high values for within-head translocation of nitrogen to grain could have been due, partly at least, to more complete translocation of glume nitrogen to grain than in the other cultivars. Speculations are made on how the wheat phenotype might be structurally modified through breeding to bring about a greater efficiency of nitrogen translocation to the grain. © 1979 CSIRO.