Effect Of Cutting Root Vertically At Different Horizontal Distance On Grain Development And Yield Of Summer Maize

The experiments were conducted in 2014-2015 at the Technological Innovation Center of Maize in Huang-Huai-Hai Region(N36°18', E117°12') and the State Key Laboratory of Crop Biology, located at Shandong Agriculture University in Taian. Two summer maize cultivars, ZD958(shallow root type) and DH661(deep root type) were planted in the field. At the bugle stage, we cut root vertically at different horizontal distance of 10 cm, 20 cm and 30 cm in a 60 cm deep, remember to respectively as ZDCK, ZD10, ZD20, ZD30 and DHCK, DH10, DH20, DH30. The regulation effects of roots at different positions on grain develop and yield of summer maize were studied to providind the theory basis for further improve the grain yield of summer maize through adjusting the root system distribution and function. 1. Effect of cutting root vertically at different horizontal distance on rootThe root of ZD958 and DH661 reduced 24.81%, 11.69% and 16.82%, 7.52%, respectively, after cutting root vertically at distance of 10 cm and 20 cm, cutting root changed the distribution of root, especially the ratio of deep root. The ratio of deep root of DH661 significantly higher than ZD958, and the impact degree of DH661 on growth and ecological function of aboveground part was lower than ZD958. 2. Effect of cutting root vertically at different horizontal distance on yieldYield of two cultivars deduced significantly after cutting root vertically at distance of 10 cm and 20 cm, and the decreased magnitude of ZD958 was higher 3.28%, 4.46% than DH661, Low grains per ear and 1000-grains weight is the reason which reflect the decline in yield. Grain setting rate and grain sink also had different decrease, with the distance narrowed, it become exacerbate. 3. Effect of cutting root vertically at different horizontal distance on dry matter and nitrogen accumulationCutting root vertically at distance of 10 cm and 20 cm significantly reduced the plant assimilation capacity, especially dry matter accumulation after flowering, ZD10, ZD20 and DH10, DH20 decreased 7.75%, 2.98 and 4.64%, 2.17% respectively. Nitrogen absorption capacity of summer maize declined after cutting root, the amount of nitrogen of vegetative organs to transport grain sink increased, the values of ZD958 and DH661 are 12.75%, 7.41% and 10.19%, 5.95%, it had a greater impact on ZD958.4. Effect of cutting root vertically at different horizontal distance on grain endosperm cells proliferation and grain fillingGrain weight increase depends not only on how many summer maize endosperm cells, but also on the substance of the endosperm cells that is enriched grain filling. After cutting root at different distance, the trend of the number of endosperm cells is CK>T-20>T-10. Endosperm cell proliferation rate and active period declined after cutting root, with the distance narrowed, it become exacerbate, and ZD958 had a greater impact. Tmax, Wmax, Gmax and P also declined after cutting root, leading to weight decline of grain, and had a significant impact on ZD958. 5. Effect of cutting root vertically at different horizontal distance on grain endogenous hormoneCutting root vertically at distance of 30 cm had no effect on grain endogenous hormone, others had significant effect. Cutting root declined content of IAA and ZR, the trend is CK>T-20>T-10, this is also be the cause of low grain filling and endosperm cell proliferation rate. The trend of ABA is CK>T-20>T-10 in early grain filling after cutting root when late grain filling had a contrary trend. With the increase of days after anthesis, the content of GA had down trent, showed T-10>T-20>CK, higher content of GA in early grain filling is harmful to grain filling of T-10 and T-20.