Controlled- or slow-release urea can improve crop nitrogen use efficiencies and yields in many agricultural production systems. The effect of controlled-release urea on the relationships between levels of gene expression and yields has not been adequately researched. We conducted a 2 year field study with direct-seeded rice, which included treatments of controlled-release urea at four rates (120, 180, 240, and 360 kg N ha–1), a standard urea treatment (360 kg N ha–1), and a control treatment without applied nitrogen. Controlled-release urea improved the inorganic nitrogen concentrations of root-zone soil and water, functional enzyme activities, protein contents, grain yields, and nitrogen use efficiencies. Controlled-release urea also improved the gene expressions of nitrate reductase [NAD(P)H] (EC 1.7.1.2), glutamine synthetase (EC 6.3.1.2), and glutamate synthase (EC 1.4.1.14). With the exception of glutamate synthase activity, there were significant correlations among these indices. The results showed that controlled-release urea improved the content of inorganic nitrogen within the rice root zone. Compared with urea, the average enzyme activity of controlled-release urea increased by 50–200%, and the relative gene expression was increased by 3–4 times on average. The added soil nitrogen increased the level of gene expression, allowing enhanced synthesis of enzymes and proteins for nitrogen absorption and use. Hence, controlled-release urea improved the nitrogen use efficiency and the grain yield of rice. Controlled-release urea is an ideal nitrogen fertilizer showing great potential for improving rice production.
A reproducible stationary improved confinement mode (I-mode) has been achieved recently in the Experimental Advanced Superconducting Tokamak, featuring good confinement without particle transport barrier, which could be beneficial to solving the heat flux problem caused by edge localized modes (ELM) and the helium ash problem for future fusion reactors. The microscopic mechanism of sustaining stationary I-mode, based on the coupling between turbulence transition and the edge temperature oscillation, has been discovered for the first time. A radially localized edge temperature ring oscillation (ETRO) with azimuthally symmetric structure (n = 0,m = 0) has been identified and it is caused by alternative turbulence transitions between ion temperature gradient modes (ITG) and trapped electron modes (TEM). The ITG-TEM transition is controlled by local electron temperature gradient and consistent with the gyrokinetic simulations. The self-organizing system consisting with ETRO, turbulence and transport transitions plays the key role in sustaining the I-mode confinement. These results provide a novel physics basis for accessing, maintaining and controlling stationary I-mode in the future.
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