| Split plot 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. The experiments were carried out with the combination of field and soil column cultivation. Eight varieties that have been bred from 1980 S to date, Yedan 13(YD), Nongda 108(ND), Zhengdan 958(ZD), Xianyu 335(XY), and Jingke 968(JK), Zhongdan 909(AD), Denghai 605(DHA), Denghai 618(DHB), were used and two nitrogen levels: 236.25 and 0 kg·hm-1 in the field, 4.5(HN) and 1.5(LN) g·plant-1 in the soil column were designed. Regular sampling of root and plant for determination of root system, dry matter and nitrogen accumulation and distribution. Through the study of the response of root architecture and anatomical structure to nitrogen application rate to prove the evolution of root architecture and anatomical structure and its relationship with nitrogen uptake and utilization in the process of maize yield promotion. Therefore, it can provide theoretical basis for improving the yield and nitrogen use efficiency of maize. The main results were as follows: 1. Yield and Biomass per plant increased in modern maize varietiesAll varieties had higher grain yield and biomass per plant under high nitrogen condition. Grain yield was increased and more significantly under low nitrogen condition with the replacement of maize varieties which indicating that the breeding process increase the production, but also improve the grain yield under low nitrogen level. The biomass accumulation of the modern varieties showed an increasing trend, and the dry matter accumulation in post-anthsis was also higher than before cultivars. It showed that the breeding process increased the biomass accumulation which increased the yield significantly. 2. Nitrogen accumulation and Nitrogen use efficiency increased in modern maize varietiesThe amount of nitrogen accumulation in modern varieties was significantly higher than early varieties especially under low nitrogen conditions which indicated that modern varieties can still absorb more nitrogen under nitrogen deficiency. The amount and the proportion of nitrogen accumulation in post-anthsis of the modern cultivars were significantly higher than those in the early varieties, so the breeding process especially increased the accumulation of nitrogen in post-anthsis. Modern maize Nitrogen uptake efficiency and harvest index of modern varieties also showed a significant increasing trend especially in low nitrogen conditions of nitrogen, indicating that the proportion of N uptake by modern varieties to grain transport increased greatly, which was beneficial to the increase of yield. 3. Higher seminal root number, more deep root and optimized root anatomical structure in modern maize varietiesNodal root number, Root dry weight, Root length and root surface area show a trend of decrease in the first and then increase over time with the replacement of varieties, The increase of the root biomass of modern varieties can provide enough nutrients for the yield. The number of seminal root increased gradually with the change of varieties which was conducive to the growth of plants at the seedling stage. The lateral root density decreased of modern varieties which reduced root competition caused by root aggregation, this made it profitable to take nutrients in soil. D95 of the modern varieties increased than before. It showed that the deep root penetration increased. Root cortical aerenchyma(RCA) for root cross-sectional area ratio and cortical cell size(CCS) increased but the number of cell files(CCFN) decreased with the change of varieties in root anatomic structure, these changes can reduce root respiration to avoid the consumption of root metabolism in the process of root weight increase, which is beneficial to increase the efficiency of nitrogen use and increase grain yield. |
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