| This study investigated the effects of different nitrogen topdressing levels on the photosynthetic characteristics, grain quality, and yield of the strong gluten wheat cultivar 'Shangyou 1'. Five nitrogen application levels were tested: N30, N60, N90, N120, and N150 (kg/hm2). The results showed that the SPAD values of leaves at anthesis, grain filling, and maturity stages initially increased and then decreased with higher nitrogen rates, peaking at N120. Within the range of 30~120 kg/hm2, increasing nitrogen significantly enhanced the net photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate (Tr), while further increases beyond this range led to declines in these parameters. Conversely, intercellular CO2 concentration (Ci) decreased with increasing nitrogen, reaching its lowest value at N120. Grain protein content, bulk density, and dough stability time improved significantly with increasing nitrogen rates, while wet gluten content and water absorption were not significantly affected. However, excessive nitrogen application (N150 kg/hm2) had a negative effect on grain quality. Plant height, spike number per unit area, and kernel number per spike increased with nitrogen input, whereas 1,000 grain weight and overall yield showed an initial increase followed by a decline, again peaking at N120. Overall, considering photosynthetic efficiency, yield, and grain quality, a nitrogen topdressing rate of 120 kg/hm2 is optimal for achieving high yield and superior quality in 'Shangyou 1'. |
