CARBON AND NITROGEN FLOWS IN HYBRID WHEAT S AND THEIR PARENTS DURING GRAIN FILLING

Carbon and nitrogen flows were studied between anthesis and maturity o n 29 hybrid wheats and their 23 parents examined in a complete block d esign, the basic plot measuring 7 m(2). Heterosis expressed not only f or grain yield but also for nitrogen yield. With the same nitrogen fil ling rate per m(2), F1 had a greater duration of grain filling for nit rogen than inbred lines. For the hybrids and their parents, 65% of gra in nitrogen was already in the plant at anthesis, when only 18% of gra in glucides came from water-soluble carbohydrate remobilization. There was no difference between hybrids and inbred lines for remobilization , but post-anthesis assimilation of nitrogen was greater for the Fl hy brids than for their parents. Some assumptions regarding carbon-nitrog en relationships are proposed to explain the more favorable 'sink-sour ce' relationship demonstrated for the hybrids.