Glutenin macropolymer particles distribution in wheat grain in relation to nitrogen topdress stage

Glutenin macropolymer (GMP) particles distribution of wheat is an important characteristic that can affect its chemical composition and functionality. Nitrogen fertilization has been studied extensively; however, little is known about the effect of nitrogen application stage on GMP particles distribution in wheat. In the present study, two wheat cultivars, Jinan 17 (strong gluten winter wheat) and Lumai 21 (weak gluten winter wheat), were used to investigate the effects of nitrogen topdressing stage on the size distribution of GMP in grains. The nitrogen fertilizer rate during the whole growth period was 225 kg ha -1 , of which a half was applied as base fertilizer and the other half was topdressed at returning green (RE), jointing (JT) or booting (BT) stage. Results showed that the contents of GMP and the percentage of large GMP particle volume in Jinan 17 were higher than that in Lumai 21, which indicated that more glutenin is accumulated in the strong gluten cultivar than in the weak gluten cultivar. At maturity, the contents of GMP in Jinan 17 showed decreasing trends with the delay of topdressing practice, and the highest values were observed in the RE treatment. In Lumai 21, compared to the RE and BT treatments, the JT treatment significantly accelerated the GMP accumulation. For both cultivars, delay of nitrogen topdressing enhanced the percentages of volume and surface of GMP particle with diameter less than 12 µm, but reduced those of GMP particle with diameter larger than 100 µm. The percentage of GMP particle number with diameter larger than 12 µm was increased in Jinan 17 with the delay of nitrogen topdressing but decreased in Lumai 21.