Abstract:

More attention has been paid to wheat grain falling number (GFN) that is an important index indicating α-amylase activity and quality property of wheat. Limited published information of GFN dynamics and the effects of environmental conditions on it during grain filling are known. In the present paper, the field experiments of N and P application and sowing date in Harbin in 2002 were conducted to investigate the dynamic pattern in GFN and how it was affected by the N and P fertilizer and meteorological conditions during grain filling using three genotypes of spring wheat with high protein-rich gluten (Wildcat), high protein-medium gluten (DN7742) and low protein-poor gluten（NKH9）. The N and P application treatments included F1 (N: 225 kg/ha, P₂O₅: 450 kg/ha)，F2 (N: 300 kg/ha, P₂O₅: 300 kg/ha), F3 (N: 300 kg/ha, P₂O₅: 450 kg/ha) and F4 (N: 300 kg/ha, P₂O₅: 600 kg/ha). The least squares method was used to finish the curve fitting of the dynamic pattern in the grain falling number. The results showed that the dynamic changes in GFN with the increase of days after anthesis could be fitted to a third-order convex curve，i.e. GFN rose in the initial stage and then fell in mid-late stage, and the effects of genotypes and environmental factors on GFN could be expressed by the coefficients and characteristic variables of the curve equation. From the 15th day after anthesis to maturity, with increasing nitrogen in medium phosphorus under high kalium level, GFN and the curve highest value were increased and its corresponding time postponed in high protein-rich gluten genotype, but there were on the contrary in both high protein-medium gluten and low protein-poor gluten genotypes. And GFN in the three genotypes all decreased with increasing phosphorus in medium or low nitrogen and high kalium level, and the characteristic variables of the curve equations varied with different genotypes. The balance fertilization of nitrogen, phosphorus and kalium was the key to get a higher GFN (lower α-amylase activity). Under the condition of moderate rainfall, the interaction of temperature and sunlight was the predominant factor affecting GFN in different genotypes during grain filling, and rainfall was the second one; PAR was the most sensitive meteorological element influencing GFN dynamics. The interaction of higher sunlight and temperature was the basis of higher GFN in different genotypes. Under the precondition of the interaction of higher sunlight and temperature, GFN in high protein-rich gluten genotype was increased with increasing PAR in a certain range while decreased when PAR was beyond the range in both high protein-medium gluten and low protein-poor gluten genotypes. The effects of meteorological conditions and differences among genotypes could be indicated by the dynamic curve changes. High protein-medium gluten and lower proten-poor gluten genotypes were affected more by nitrogen and phosphorus fertilizer but less by meteorological conditions than high protein-rich gluten genotype. Comparatively, high protein-rich gluten genotype was more sensitive to meteorological factors while high protein-medium gluten and lower protein-poor gluten genotypes were more sensitive to nitrogen and phosphorus fertilizer.

Key words: Spring wheat, Grain falling number (GFN), Dynamic formation, Nitrogen and phosphorus fertilizer, Sowing date