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Background: Nitrogen management of crops, especially when mid-stage nitrogen is applied, is a key factor affecting the yield and grain quality of rice (Oryza sativa). Here, the timing of mid-stage nitrogen application was evaluated for its effect on rice grain quality by assessing the morphological structure and physicochemical properties of starch from two japonica rice cultivars growing in fields (Nangeng 9108 and Nangeng 5055)., Results: The experiment was arranged in a split-plot design, with the two rice cultivars as the main plot factor and three timings of mid-stage nitrogen application as the within-plot factor. Briefly, three applications were made: at the emergence of the top-sixth-leaf (ahead), the top-fourth-leaf (normal), and the top-second-leaf (delayed) of the main stem. Delaying mid-stage nitrogen application caused the starch granule surface to become uneven and significantly reduced its particle size, whereas it increased the polished rice rate, chalkiness degree, and protein content. Furthermore, the apparent amylose content decreased with a delay in mid-stage nitrogen application, thereby resulting in higher relative crystallinity, swelling power, water solubility, gelatinization enthalpy, and low retrogradation. Finally, we also found that delaying this nitrogen application lowered the characteristic values of rice flour viscosities, leading to cooking quality deterioration., Conclusion: These results therefore suggest that delaying mid-stage nitrogen application enhances the processing and nutritional qualities of japonica rice but evidently has an adverse effect upon its appearance and cooking qualities. © 2020 Society of Chemical Industry., (© 2020 Society of Chemical Industry.)

The hydrosilylation of unsaturated carbon-heteroatom (C═O, C═N) bonds catalyzed by high-valent rhenium(V)-dioxo complex ReO2I(PPh3)2 (1) were studied computationally to determine the underlying mechanism. Our calculations revealed that the ionic outer-sphere pathway in which the organic substrate attacks the Si center in an η(1)-silane rhenium adduct to prompt the heterolytic cleavage of the Si-H bond is the most energetically favorable process for rhenium(V)-dioxo complex 1 catalyzed hydrosilylation of imines. The activation energy of the turnover-limiting step was calculated to be 22.8 kcal/mol with phenylmethanimine. This value is energetically more favorable than the [2 + 2] addition pathway by as much as 10.0 kcal/mol. Moreover, the ionic outer-sphere pathway competes with the [2 + 2] addition mechanism for rhenium(V)-dioxo complex 1 catalyzing the hydrosilylation of carbonyl compounds. Furthermore, the electron-donating group on the organic substrates would induce a better activity favoring the ionic outer-sphere mechanistic pathway. These findings highlight the unique features of high-valent transition-metal complexes as Lewis acids in activating the Si-H bond and catalyzing the reduction reactions.

The carbon and nitrogen (N) metabolism of rice under different mid-stage N compensation timings is unclear. Two Japonica super rice cultivars were examined under four N compensation timings (N1-N3: N compensation at mid-tillering, panicle initiation, and spikelet differentiation. N0: no N compensation) and CK with no N application. Mid-stage N compensation increased the N concentrations of various tissues, and N2 showed the highest plant N uptake at both the heading stage, maturity, and the grain filling period. Among the treatments, N2 showed the highest N utilization efficiency. With delayed compensation timing, there was a gradual decrease in soluble sugar and starch concentrations in each tissue, accompanied by a decline in the non-structural carbohydrate (NSC) concentration. Specifically, N2 treatment exhibited the highest NSC accumulation and the remobilized NSC reserve, but NSCs per spikelet decreased with delayed compensation timing. The highest yield was also obtained with N2, exhibiting a 4.5% increase compared to the N0 treatment, primarily due to an improvement in spikelets per panicle. Conclusively, N compensation at the panicle initiation stage is a reasonable N management strategy that can coordinate the improvement of carbon and N metabolism, enhance N accumulation with efficient utilization and NSC accumulation, and ultimately increase the yield. [ABSTRACT FROM AUTHOR]

The production of ammonia (NH3) from nitrogen sources involves competitive adsorption of different intermediates and multiple electron and proton transfers, presenting grand challenges in catalyst design. In nature nitrogenases reduce dinitrogen to NH3 using two component proteins, in which electrons and protons are delivered from Fe protein to the active site in MoFe protein for transfer to the bound N2. We draw inspiration from this structural enzymology, and design a two‐component metal–sulfur–carbon (M−S−C) catalyst composed of sulfur‐doped carbon‐supported ruthenium (Ru) single atoms (SAs) and nanoparticles (NPs) for the electrochemical reduction of nitrate (NO3−) to NH3. The catalyst demonstrates a remarkable NH3 yield rate of ~37 mg L−1 h−1 and a Faradaic efficiency of ~97 % for over 200 hours, outperforming those consisting solely of SAs or NPs, and even surpassing most reported electrocatalysts. Our experimental and theoretical investigations reveal the critical role of Ru SAs with the coordination of S in promoting the formation of the HONO intermediate and the subsequent reduction reaction over the NP‐surface nearby. Such process results in a more energetically accessible pathway for NO3− reduction on Ru NPs co‐existing with SAs. This study proves a better understanding of how M−S−Cs act as a synthetic nitrogenase mimic during ammonia synthesis, and contributes to the future mechanism‐based catalyst design. [ABSTRACT FROM AUTHOR]

One-time fertilization with controlled-released fertilizer (CRF) is a promising way for reducing labor cost, increasing nitrogen use efficiency (NUE) and alleviating environmental pollution in winter wheat (Triticum aestivum L.) cultivation. However, CRF release characteristics are related to various factors such as soil properties, temperature and precipitation, and further study is needed in developing suitable fertilizer formulas adapting to local conditions. In this study, five types of CRF were used for a one-time application in a two-year field experiment conducted at two sites with two wheat cultivars. Their effects on soil inorganic nitrogen (SIN) content, nitrogen uptake, wheat growth and grain yield were investigated. The results indicated that nitrogen supply in the CRF-60/80 treatments not only ensured the tiller differentiation at the early growth stage, but also provided adequate SIN after the jointing stage, thereby facilitating the dry matter accumulation and improving post-anthesis photosynthates accumulating in grains. When compared with conventional split fertilization, the CRF-60 and 80 treatments improved the NUE by 9.7–12.1%, and boosted farmers' economic efficiency by 282.4–327.2 CNY ha−1. According to our research, a one-time application of CRF-60 and CRF-80 could meet the needs of the two-peak nitrogen demand of wheat in Jiangyan and Yanghzou respectively, therefore increasing NUE and having low labor costs for wheat fertilizer application. [ABSTRACT FROM AUTHOR]

A one-off application of bulk blend urea (BBU), which includes a controlled release urea formula and conventional urea, has been recommended to simplify fertilisation management for direct-seeded rice. However, the effects of different basal application ratios of controlled-release urea formula and conventional urea on yield and nitrogen (N) use efficiency remain unknown in direct-seeded rice. This study set up three BBU treatments in which the controlled-release urea formula provided 50% (BBU1), 60% (BBU2), and 70% (BBU3) of the total N. This study measured their effects on grain yield and N use efficiency of direct-seeded rice. Split fertilisation with conventional urea was used as the control (CK). The study concluded four key points: (i) the grain yield of direct-seeded rice decreased as the proportion of controlled-release urea formula increased, (ii) BBU1 increased grain yields by 8.1–8.6% and 10.2–10.6% compared to BBU2 and BBU3, respectively, as well as a greater number of panicles and spikelets per m2, and post-anthesis dry matter accumulation, (iii) the N recovery efficiency and N agronomic efficiency of BBU1 were significantly higher than those of BBU2 and BBU3 treatments, and the nitrogen accumulation was also found to be more, and (iv) compared with the CK, BBU1 achieved considerable grain yield and nitrogen use efficiency while reducing the amount of fertilisation. In conclusion, the appropriate reduction of the basal application ratio of the controlled-release urea formula for direct-seeded rice increased grain yield and nitrogen use efficiency. [ABSTRACT FROM AUTHOR]

Fertilization is an important practical measure in agricultural production. As an important nutrient element of plants, nitrogen (N) has a significant impact on the plant productivity and microbial function. Rhizosphere microorganisms affect plant growth and development, nitrogen uptake and utilization, and ecological adaptability. The interaction mechanism between plant and rhizosphere microorganisms is one of the hotspots in life science research and the key program of agricultural microorganism utilization. In this article, the relationship among plant root morphology and physiology, rhizosphere microorganisms, and nitrogen is reviewed, summarized, and prospected. [ABSTRACT FROM AUTHOR]

The main purpose of the present study was to explore the optimum timing for mid-stage nitrogen (N) application to improve fragrant rice performance. The field experiment was conducted in 2019 and 2020 with two fragrant rice cultivars, i.e., YNX28 and NG9108, and five timings of mid-stage nitrogen application: at the emergence of the top-fifth-leaf (TL5), the top-fourth-leaf (TL4), the top-third-leaf (TL3), the top-second-leaf (TL2), and the top-first-leaf (TL1) of the main stem. The control condition received no mid-stage nitrogen application (CK). The results revealed that the TL5, TL4, TL3 and TL2 treatments significantly increased grain yield of both varieties in 2019 and 2020, compared with CK. Grain yield reached a maximum value under the TL3 treatment of YNX28 and the TL4 treatment of NG9108. Moreover, the TL4, TL3 and TL2 treatments significantly increased the brown rice rate, milled rice rate, head rice rate and protein content of both varieties in 2019 and 2020, compared with CK, whereas the TL2 and TL1 treatments of YNX28 and the TL3, TL2 and TL1 treatments of NG9108 significantly increased the chalky rice rate and chalkiness. Further, appropriate mid-stage nitrogen application timing also improved the grain 2-AP content due to regulation of the contents of synthesis-related precursors (proline, GABA) and enzymatic activities (ProDH, OAT, P5CS, BADH2). Compared with CK, the TL4 and TL3 treatments of YNX28 significantly increased the 2-AP content in the rice grains by 21.8–27.4%, while the TL5 and TL4 treatments of NG9108 significantly increased the 2-AP content in the rice grains by 15.6–31.6%. These results suggest that the TL3 treatment of YNX28 and the TL4 treatment of NG9108 are the optimum timings of mid-stage nitrogen application for fragrant rice production. The optimal mid-stage nitrogen application timing of NG9108 is earlier than that of YNX28. • Delayed timing of mid-stage nitrogen application deteriorated the appearance quality of rice. • Appropriate mid-stage nitrogen application timing also improved the grain 2-AP content. • In terms of 2-AP and its synthesis-related parameters, TL4 of NG9108 and TL3 of YNX28 differed most from CK treatment. [ABSTRACT FROM AUTHOR]