Abstract: 【Objective】In recent years, the declining trend of global solar radiation has become a limiting factor in crop production, low light is one of the most important stresses to maize growth and yield formation. This study was conducted to investigate the effects of different light intensities on the root growth and yield of summer maize under field conditions. 【Method】In 2012-2014, Denghai 605 (DH605) was used as experimental material. Two treatments of both shading (S) and increasing light (L) from flowering to maturity stage during maize growth period were designed. The field experiment was conducted to explore the effects of different light on dry matter accumulation, root structure characteristics and yields of summer maize. The shading degree was 60% and the illumination intensity of the increasing light on cloudy day could reach 80 000-10 0000 lx. One non-shading and non-increasing light treatment was used as control. 【Result】 Compared to CK, root characteristics and grain yield under shading decreased, while those of L increased. Results showed that grain yields in S treatment were reduced by 79%, 61% and 60% from 2012 to 2014, compared to CK, while the yields in L treatment were increased by 13%, 7% and 15%. Yield, root/shoot ratio, root diameter, root length density, root absorption area and root active absorption area decreased, respectively, after shading from flowering to maturity stage; however, the yield, root/shoot ratio, root diameter, root length density, root absorption area and root active absorption area increased after increasing light from flowering to maturity stage. Shading had a strong impact on the development of roots in the upper soil layer, while roots in lower soil layers were less affected. Shading from flowering to maturity stage clearly decreased the photosynthetic rate, leaf pigments content, dry matter accumulation, root/shoot ratio, root length density, root absorption area and active absorption area. Overall, shading from flowering to maturity stage decreased the root morphologic and activity indices. Increasing light was beneficial to the improvement of the root of the robust growth and root activity. The root absorption areas in the 0-30 cm and 30-60 cm soil layers in L increased by 17%, 18%, 17% and 21%, 27%, 27% at VT+20, VT+40, and R6, respectively, compared to the control. The root active absorption areas increased by 11%, 18%, 17% and 27%, 33%, 28% at VT+20, VT+40, and R6, respectively, compared to the control. Increasing light made the plants could get more water and nutrients from the soil for the growth of the aerial part, increasing grain filling rate and grain yield. 【Conclusion】 In latter growing period, root characteristics and grain yield decreased under shading, while those of L increased. In order to fit rainy weather in latter period, the study suggest that adjusting plant date and optimizing management should be done to mitigate shading in this region.

Key words: summer maize, shading, increasing light, root characteristics, grain yield