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Postanthesis Nitrate Assimilation in Winter Wheat ¹

In Situ Flag Leaf Reduction

United States Department of Agriculture, Agricultural Research Service, University of Kentucky, Lexington, Kentucky 40546-0091, Department of Agronomy, University of Kentucky, Lexington, Kentucky 40546-0091

When adequate levels of soil NO₃^– are available, concurrent NO₃^– absorption and assimilation, and mobilization of vegetative N reserves accumulated prior to anthesis, may be used to supply N to developing wheat (Triticum aestivum L.) kernels. Vegetative wheat components (stems, leaves, spike) are known to possess NO₃^– reductase activity, but the in situ utilization of NO₃^– translocated to the shoot has not been studied. Assimilation and partitioning of ¹⁵N was determined in winter wheat `Doublecrop.' At 7 days after anthesis, the stem immediately above the peduncle node was heat girdled to block phloem export from the flag leaf. Control plants were not girdled. One day later, 50 micromoles of ¹⁵NO₃^– (98 atom percent ¹⁵N) was injected into the penultimate internodal lacuna, after which ¹⁵NO₃^– utilization was determined sequentially over a 5 day period. Based on differences in spike accumulation of reduced ¹⁵N excess between treatments and the amount of reduced ¹⁵N excess remaining in the flag leaf, it was estimated that the flag leaf contributed 37% of the total reduced ¹⁵N excess in the injected shoot. The lower shoot contribution was 18% and that of the peduncle plus spike was 45%.

This article has been cited by other articles:

				C. T. MacKown and B. F. Carver Nitrogn Use and Biomass Distribution in Culms of Winter Wheat Populations Selected from Grain-Only and Dual-Purpose Systems Crop Sci., February 6, 2007; 47(1): 350 - 358. [Abstract] [Full Text] [PDF]