[Canopy light distribution and its correlation with photosynthetic production in super-high yielding cotton fields of Xinjiang, Northwest China].

Taking the super-high yielding cotton fields (lint yield > or = 4000 kg x hm(-2)) in Xinjiang as the objects, this paper studied the canopy light distribution, photosynthetic rate, and dry matter accumulation at different growth stages, as well as the relationships between the characteristics of canopy light environment and the photosynthetic production. From full flowering stage to late full bolling stage, the light absorption proportion in the upper, middle and lower canopy layers in the super-high yielding cotton fields was 2:2:1, and the canopy transmission coefficients for radiation penetration and diffuse penetration were 0.20-0.55 and 0.22-0.56, respectively, being at reasonable level. The leaves in the middle and lower canopy layers could well accept light, and the leaf photosynthetic rate had little difference among different canopy layers. Compared with high yielding (3500 kg x hm(-2)) and generally high yielding (3000 kg x hm(-2)) cotton fields, super-high yielding cotton field had higher leaf area index and the highest canopy photosynthesis rate at early full boiling stage, and slowly decreased leaf area index, higher canopy photosynthesis rate, increased contribution of non-foliar organs to photosynthetic production, and larger dry matter accumulation from early boll-opening stage to full boll-opening stage. In cotton cultivation, to adjust the canopy structure for the equidistribution of light and canopy photosynthesis capacity in vertical direction could be the important strategy for the efficient utilization of absorbed light energy and the realization of super-high yielding.