Abstract:

Nitrogen fertilizer is one of the most important factor to influence the carbon and nitrogen metabolism as well as the growth and development of crops. The objective of this study was to compare the fructan accumulation and translocation as well as their heterosis in different organs at various growth stages using six hybrids of wheat and their seven parents grown by a split plot design with two replications under two levels of nitrogen applications 0 kg/hm² and 200 kg/hm². Above-ground plant parts were harvested at 75, 90, 105, 120, 140, and 160 d after sowing, corresponding with stages of stem elongation, flag leave emergence, heading, flowering, milk-ripe and maturity, respectively. The samples were partitioned into leaf, stem and sheath, stalk and chaff of spike, and grain, then microwaved for 4 min, and dried in oven at 60℃. Fructan content of the hammermill-ground sample and grain nitrogen content were determined by Near Infrared Reflectance spectrometry.
Significant differences between nitrogen application levels in fructan accumulation and content were observed in all vegetative organs at most sampling dates. Genotypic differences were found at heading stage, flowering stage and milk-ripe stage. The patterns of fructan accumulation in stem and sheath and total straw were similar under two nitrogen application levels. The most fructan, about 63%–87% of the fructan accumulation of total straw, was stored in stem and sheath, and the maximum fructan accumulation was at anthesis (Fig.1). Fructan translocation of stem and sheath, which accounted for more than 85% of that of total straw, showed the highest contribution to grain yield (9.42%–19.39%) (Table 2). Fructan accumulation in leaf was reduced, but that in stem and sheath and total straw were increased under nitrogen deficiency. The heterosis of fructan accumulation (4.7%–51.7%) of stalk and chaff of spike, stem and sheath, and total straw, were appeared at flag leaf emergence, heading stage and flowering stage (Table 1). Also, there were high heterosis for fructan translocation and fructan translocation efficiency of leaf, stem and sheath and total straw. The heterosis of fructan translocation was enhanced in leaf, while decreased in stem and sheath and total straw for nitrogen application (Table 3). In conclusion, the fructan capacity translocation from vegetative organs to grain is stronger in hybrid wheat than in their parents, and the fructan accumulation and translocation as well as their heterosis in stem and sheath were restrained by nitrogen application.

Key words: Hybrid wheat, Fructan, Accumulation and translocation, N application, Heterosis, Stem and sheath