Assimilation and Partitioning of Photosynthate and Nitrogen in Isogenic Tall, Semidwarf, and Doubledwarf Winter Wheats

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Abstract
Patterns of assimilation and partitioning of photosynthate and nitrogen in isogenic tall, semidwarf, and doubledwarf (Norin 10/5/Pawnee) ‘Pawnee’ hard red winter wheats (Triticum aestivum L.) were studied under controlled environmental conditions and field conditions. The objective of the investigations was to determine reasons for the advantageous harvest index associated with dwarf genes. Plants were sampled at four growth stages and separated into plant parts as they developed. Ribulose bisphosphate carboxylase (RuBPC) and nitrate reductase (NR) activities in leaves differed among growth stages but not among isogenic lines. Fructosan in sheaths, stems, and roots increased from the soft dough stage to maturity, but differed little among the lines. Nitrogen concentrations decreased in leaf blades, stems, and roots as plants developed to the soft dough stage and then stayed nearly constant until maturity. Nitrogen in all plant parts frequently varied directly with the complement of dwarfing genes, being lowest in the tall line and highest in the doubledwarf line. The tall and semidwarf lines had significantly higher grain yield, test weight, total dry matter, spike number, and 1000‐kernel weight than the doubledwarf line under either or both experimental conditions. The dwarf lines, however, had significantly higher kernel number per spike than the tall line. Harvest index was higher for the doubledwarf line (0.58) than for the two other lines (0.54).