| Canopy structure and photosynthesis of winter wheat grown in Northern Henan province were studied under limited irrigation conditions(only irrigation at elongation).Five nitrogen(N) treatments: N4(120+210 kg·hm-2, means pre-sowing N and top-dressed N at elongation), N3(120+150 kg·hm-2), N2(120+90 kg·hm-2), N1(120+0 kg·hm-2) and N0(0+0 kg·hm-2) were conducted, and the N rate of N4 treatment was traditional N application rate during wheat growing season.Results showed that the decrease of N rate reduced leaf area per stem, the area of top three leaf blades, and the area of non-leaf organs above flag leaf node by 9.7%-28.0%, 10.6%-30.3% and 5.2%-16.8%, respectively, indicating leaf area per stem and the area of top three leaf blades were decreased more than the area of non-leaf organs above flag leaf node with decreased N application.Moreover, the decrease of N rate reduced the proportion of green leaf organs area to total green area but increased the proportion of green non-leaf organs area to total green area, and also increased the proportion the area of non-leaf organs above flag leaf node to the area of top three leaf blades.The decrease of N rate reduced the length and width of top three leaf blades by 4.4%-8.8% and 11.8%-15.6%, respectively, while the length and width of top four leaves were not affected by the decrease of N rate, suggesting the decrease of leaf area per stem was mainly attributed to the decrease of the area of top three leaf blades, whilst the decrease of the area of top three leaf blades was mainly contributed to the decrease of leaf length and width and also related to leaf width.The average specific leaf weight of top three leaf blades was increased with the decease of N application, which indicted that low nitrogen application may improve the quality of top three leaf blades.After anthesis, light transmission rate in each leaf layer was increased with the decrease of N rate.From anthesis to 20 days after anthesis, the light transmission rate of top 4th leaf layer, top 3rd leaf layer, top 2nd leaf layer, and flag leaf layer were increased by 39.0%, 38.0%, 23.8%, and 9.4%, respectively, under lower N treatments compared to those under N4 treatment, indicating the light distribution in lower and middle canopy was improved by lower nitrogen application.Photosynthetic rate of top three leaf blades first increased slightly then decreased with the decrease of N rate after anthesis, and the photosynthetic rate of flag leaf and top 2nd leaf were greater under N4, N3, and N2 treatments than those under other N treatments during grain filling period, while from anthesis to 18 days after anthesis, the photosynthetic rate of top 3rd leaf under N3 and N2 were increased by 38.7% and 24.7%, respectively, in comparison with that of N4, which indicated that lower nitrogen application did not decline the photosynthetic rate in top leaf blades, but also increased the photosynthetic rate in lower leaf blades, which were associated with enhanced light distribution in lower canopy under lower nitrogen application.The results indicated that lower nitrogen application reduced leaf area per stem and increased the percentage of non-leaf area to total green area in stem.Meanwhile, higher light transmission ratio in the lower canopy was achieved with decreasing N rate, which were mainly attributed to smaller size and high quality top leaf blades.Moreover, lower nitrogen application increased the photosynthetic rate in lower leaf blades, which was associated with enhanced light distribution in lower canopy under lower nitrogen application. |
基本信息
