Effects Of Solar Radiation And Density On Root Morphology, Root-Shoot Relationship And Yield Of Different Spring Maize Cultivar

Crop production is a system of synergistic action between aboveground plant and underground root system.Solar radiation is an important environmental factor affecting maize growth,development and yield formation.The root system,as a fixed organ and a transport pathway for water and nutrients,is closely related to plant growth and development.Exploring the mechanism of the influence of solar radiation changes on the maize root system growth and development,and revealing the matching rule between the underground and light resources of high-yield maize populations areconducive to the coordinated realization of high-yield and high-efficient utilization of light resources.The experiments were conducted in Qitai and Yinchuan,in 2018 and 2019.The maize cultivars Xianyu 335?XY335?,Zhengdan 958?ZD958?,and Denghai 618?DH618?were used.The shading period begun at the three-leaf stage and lasted till maturity.Shading levels were15?S1?,30?S2?,and 50%?S3?of natural light,and natural light was used as a control?CK?.The planting densities were 7.5×10⁴?D1?and 12×10⁴?D2?plants/ha.In this study,the effects of solar radiation on maize yield and root growth were studied in order to provide the improvement measures for maize planting adaptability in different radiation areas and provide a theoretical basis for the selection and cultivation of maize cultivars with coordinated root and shoot.The main results were as follows:1.Effects of solar radiation on growth period and yield of maizeThe growth process of maize was affected by shading in the whole growth period.The silking period of all cultivars was postponed with the decrease of solar radiation.XY335 and ZD958 were postponed for 7 days,DH618 was postponed for 10 days.Under the same density and different light levels,the grain yield was CK>S1>S2>S3,and the yield decreased degree was S3>S2>S1>CK.With the increase of density,the decrease of maize yield of each shade treatment was further increased.Analysis based on yield level,DH618 showed better shade-resistance,followed by ZD958 and XY335.2.Effects of solar radiation on root morphology of maizeMaize root morphology indicators?root length,root surface area,root volume and root diameter?significantly decreased with the decrease of solar radiation and the decrease was larger under high density.The effect of shading on the root of shallow layer?0-20cm?was greater than that of deep layer?40-60cm?.Under low light conditions,the root lengths of the thicker root?L>4 mm?of XY335 and ZD958 and the root lengths of DH618?L?1 mm?were mainly affected.The quantitative analysis showed that for every 1 MJ m^-2 decrease in photosynthetically active radiation,the root length,the root surface area and the root volume decreased by 0.3049 m,0.0004 m² and 0.0543×10^-6 m³,respectively.The effect of the shading on root morphological was the highest for XY335,followed by ZD958 and DH618.3.Effects of solar radiation on root and shoot relationship of maizeChanges in solar radiation affected the root and shoot dry weight of maize,and the effect of solar radiation intensity on the root was greater than that on the shoot,thus affecting the root-shoot relationship.After decrease of solar radiation,the root dry weight,shoot dry weight and root:shoot ratio all decreased with the increase of shading degree.The quantitative analysis results showed that for every 1 MJ m^-2 decrease in photosynthetically active radiation,the root:shoot ratio decreased by 0.0103×10^-2.The root system of XY335 and ZD958 showed better shade-resistance,and the shade-resistance of shoot was poor,while DH618 showed the opposite trend.