氮肥和密度是影响水稻产量和资源利用效率的重要因素，通过合理调控密度可以在不减产的前提下降低氮肥投入并提高氮肥利用效率。不过，对于传统的移栽稻模式，增加种植密度意味着需要投入更多的劳动力。在当前农村劳动力短缺的背景下，这种措施无疑会加剧劳动力的供需矛盾。双季稻双直播模式是一种省工、节本的轻简化栽培措施，在该模式下调整播种密度简单易行。然而，目前关于不同氮肥和密度调控对双季稻双直播模式下超短生育期品种的产量和氮肥利用效率的影响尚不明确。因此，本研究旨在揭示氮肥和密度对产量和氮肥利用效率的影响，并探明这些影响在早、晚季之间的差异。大田试验于2018和2019年分别在湖北省武穴市和蕲春县进行，设置四个氮肥和三个播种密度处理，选用超短生育期水稻品种湘早籼6号为供试材料。结果表明，在施氮处理下，早、晚稻生育期和产量的变化范围分别为85-97天和6.32-8.23 t ha^-1。水稻产量对氮肥的响应高于对播种密度的响应。早、晚稻的最适施氮量分别为100-150 kg N ha^-1和70-120 kg N ha^-1。此外，在双季稻双直播模式中，早稻产量对氮肥的响应比晚稻更大，这主要由于早稻土壤背景氮的供应能力低于晚稻。因此，考虑早、晚季间土壤背景氮供应能力的差异对于优化双季稻双直播模式的氮肥管理策略、提高氮肥利用效率有重要的意义。

再生稻是指头季收获后，采用一定的栽培管理措施使稻茬上存活的休眠芽萌发成穗而再收获一季水稻的种植模式，具有省工、省种、省水、省药、省秧田和米质优等优点。边际效应是作物生产中的普遍现象，指边行植株由于具有更多的光照和养分，相比内行植株往往具有明显的产量优势。边际效应的挖掘与利用，对于构建水稻高产栽培模式具有重要意义。目前有关水稻边际效应的研究主要集中于常规稻作模式，而对再生稻边际效应的报道尚少。再生稻两季的边际效应有何差异，头季边行优势是否会促进再生季边际效应的发挥尚不清楚。因此，本研究在湖北省蕲春县开展为期两年的大田试验，于头季与再生季分别测定边行和中间行的产量及产量相关性状，旨在量化再生稻两季边际效应的差异以及头季边际效应对再生季边际效应的贡献。结果表明：再生稻在头季和再生季均存在明显的边际效应，且头季边际效应大于再生季。头季边际效应高达98.3%，得益于较多的有效穗数、每穗颖花数和干物质积累量。而再生季边际效应为60.9%，其中约一半由头季的边际效应所贡献。进一步分析发现，头季促进再生季边际效应发挥的原因在于头季收获时较高的稻桩干重和碳水化合物含量促进了再生季有效穗数和干物质积累量的增加。因此，增加稻桩的干物质和碳水化合物累积是提高再生季产量的有效措施。

双季稻双直播模式是一种省工、节本的轻简化栽培措施，可有效应对当前双季稻种植面积逐年下降的现状。华中地区温光资源有限，双季稻双直播模式必须选用生育期在95天左右的超短生育期品种才能保障安全生产。此外，因直播稻群体密度大、扎根浅，在实际生产中往往面临着倒伏风险高的问题。然而，目前关于超短生育期水稻品种在双季稻双直播模式下的抗倒性表现和抗倒性提高途径尚不明确。因此，本研究旨在揭示华中地区双季稻双直播模式下超短生育期水稻品种的抗倒机理。田间试验于2017-2018年在湖北省武穴市进行，设置高、低两个氮肥水平，选用四个超短生育期水稻品种为供试材料，于齐穗后15天测定倒伏相关性状。结果表明，超短生育期水稻品种在两个氮水平下的生育期和产量的变异范围分别为85-97天和4.59-7.61 t ha^-1。在该产量水平下，弯曲力矩是造成氮肥处理和品种间倒伏指数差异的主要原因，而抗折力及其他茎秆形态指标并未显著影响倒伏指数。弯曲力矩主要受株高的影响，超短生育期水稻品种的株高从95.4 cm降低至80.5 cm，弯曲力矩降低32.0%，倒伏指数降低22.4%，但是产量没有显著降低。因此，在目前的产量水平下，降低超短生育期品种株高是提高双季稻双直播模式抗倒性的有效措施。但是在未来超短生育期品种产量潜力进一步提升的进程中，育种家们更应该关注增强茎秆抗折力，以进一步提高双季稻双直播模式的产量和稳产性。

Rice research has always been the top priority in China and China produces the highest number of scientific journal papers on rice, particularly on rice genetics and breeding.  In this study, we used a bibliometric approach to analyze the trends of papers published by Chinese researchers on rice physiology and management.  Data were collected from three major agronomic journals (i.e., Agronomy Journal, Crop Science, and Field Crops Research) by searching in the Web of Science on September 8, 2017.  A total of 186 rice papers were published by Chinese researchers on crop physiology and management in the three journals since their establishment.  Yearly average number of such papers was 1.6, 6.5, and 21.0 for the periods of 1993–2005, 2006–2011, and 2012–2017, respectively.  Their quality in terms of citation performance has also improved significantly in the recent decade.  Huazhong Agricultural University, Yangzhou University, and Nanjing Agricultural University were leading organizations and published 54.4% of all 186 papers.  Huang Min of Hunan Agricultural University and Peng Shaobing of Huazhong Agricultural University published the most number of rice papers on crop physiology and management as the first and corresponding authors, respectively.  Yield potential and nitrogen-related research such as nitrogen use efficiency, nitrogen management, and plant nitrogen diagnosis have been the research focuses for rice crop.  In recent years, research on global warming including high temperature stress, direct seeding, zero tillage, Bt rice, and critical nitrogen dilution curve were becoming popular.  New research is emerging on yield gap, rice ratooning, and simplified and reduced-input practices in rice production.

In 1996, a mega project that aimed to develop rice varieties with super-high yield potential (super rice) was launched by the Ministry of Agriculture (MOA) in China using a combination of the ideotype approach and intersubspecific heterosis.  Significant progress has been made in the last two decades, with a large number of super rice varieties being approved by the MOA and the national average grain yield being increased from 6.21 t ha⁻¹ in 1996 to 6.89 t ha⁻¹ in 2015.  The increase in yield potential of super rice was mainly due to the larger sink size which resulted from larger panicles.  Moreover, higher photosynthetic capacity and improved root physiological traits before heading contributed to the increase in sink size.  However, the poor grain filling of the later-flowering inferior spikelets and the quickly decreased root activity of super rice during grain filling period restrict the achievement of high yield potential of super rice.  Furthermore, it is widely accepted that the high yield potential of super rice requires a large amount of N fertilizer input, which has resulted in an increase in N consumption and a decrease in nitrogen use efficiency (NUE), although it remains unclear whether super rice per se is responsible for the latter.  In the present paper, we review the history and success of China’s Super Rice Breeding Program, summarize the advances in agronomic and physiological mechanisms underlying the high yield potential of super rice, and examine NUE differences between super rice and ordinary rice varieties.  We also provide a brief introduction to the Green Super Rice Project, which aims to diversify breeding targets beyond yield improvement alone to address global concerns around resource use and environmental change.  It is hoped that this review will facilitate further improvement of rice production into the future.

The ecosystem services value (ESV) of rice system has received increasing attention in agricultural policy decision. Over the last three decades, China’s rice production presented an obviously trend that moving towards north locations. However, the impacts of this migration on the ESV of rice production have not been well documented. In this paper, we analyzed the change of the ESV of rice production in China under “north migration” and “no migration” scenarios during 1980–2014 based on long-term historical data. The results showed that both the positive and negative ESVs of rice production were lower under “north migration” than under “no migration” scenarios. The total ESV during 1980–2014 was reduced by 15.8%. “North migration” significantly reduced the area-scaled ESV since the early 1990s; while its impact on yield-scaled ESV was not significant. The effects of “north migration” on ESV showed great spatial variation. The greatest reduction in total and area-scaled ESV was observed in south locations. While the yield-scaled ESVs of most south locations were enhanced under “north migration” scenario. These results indicated that “north migration” has generated adverse effects on the ESV of rice production. An adjustment in the spatial distribution is essential to protecting the non-production benefits of rice ecosystem.

To compare the grain yield and growth behaviors of hybrid rice, field experiments were conducted in a subtropical environment in Changsha, Hunan Province, China, and in two tropical environments in Gazipur and Habiganj in Bangladesh during 2009 to 2011. Three hybrid rice cultivars were grown under three nitrogen (N) management treatments in each experiment. The results showed that grain yield was significantly affected by locations, N treatments and their interaction but not by cultivars. Changsha produced 8-58% higher grain yields than Bangladesh locations. Sink size (spikelet number per unit land area) was responsible for these yield differences. Larger panicle size (spikelet number per panicle) contributed to greater sink size in Changsha. Aboveground total biomass was greater in Changsha than in Bangladesh locations, whereas harvest index was higher in Bangladesh locations than in Changsha. Crop growth rate (CGR) was greater at Changsha than Bangladesh locations during vegetative phase, while the difference was relatively small and not consistent during the later growth phases. Higher leaf area index and leaf area duration were partly responsible for the greater CGR in Changsha. Real-time N management (RTNM) produced lower grain yields than fixed-time N management in more than half of the experiments. Our study suggested that further improvement in rice yield in the tropical environments similar to those of Bangladesh will depend mainly on the ability to increase panicle size as well as CGR during vegetative phase, and the chlorophyll meter threshold value used in RTNM needs to be modified according to environmental conditions and cultivar characteristics to achieve a desirable grain yield.

Poor nitrogen use efficiency in rice production is a critical issue in China. Site-specific N managements (SSNM) such as real-time N management (RTNM) and fixed-time adjustable-dose N management (FTNM) improve fertilizer-N use efficiency of irrigated rice. This study was aimed to compare the different nitrogen (N) rates and application methods (FFP, SSNM, and RTNM methods) under with- and without-fungicide application conditions on grain yield, yield components, solar radiation use efficiency (RUE), agronomic-nitrogen use efficiency (AEN), and sheath blight disease intensity. Field experiments were carried out at Liuyang County, Hunan Province, China, during 2006 and 2007. A super hybrid rice Liangyou 293 (LY293) was used as experimental material. The results showed that RTNM and SSNM have great potential for improving agronomic-nitrogen use efficiency without sacrificing the grain yield. There were significant differences in light interception rate, sheath blight disease incidence (DI) and the disease index (ShBI), and total dry matter among the different nitrogen management methods. The radiation use efficiency was increased in a certain level of applied N. But, the harvest index (HI) decreased with the increase in applied N. There is a quadratic curve relationship between grain yield and applied N rates. With the same N fertilizer rate, different fertilizer-N application methods affected the RUE and grain yield. The fungicide application not only improved the canopy light interception rate, RUE, grain filling, and harvest index, but also reduced the degree of sheath blight disease. The treatment of RTNM under the SPAD threshold value 40 obtained the highest yield. While the treatment of SSNM led to the highest nitrogen agronomic efficiency and higher rice yield, and decreased the infestation of sheath blight disease dramatically as well. Nitrogen application regimes and diseases control in rice caused obvious effects on light interception rate, RUE, and HI. Optimal N rate is helpful to get higher light interception rate, RUE, and HI. Disease control with fungicide application decreased and delayed the negative effects of the high N on rice yield formation. SSNM and RTNM under the proper SPAD threshold value obtained highyield with high efficiency and could alleviate environmental pollution in rice production.

Behaviours of urediospore germtube in Melampsora larici-populina on the leaf surface of Populus purdomii were studied by light microscope, scanning electron microscope (SEM), transmission electron microscope (TEM), and fluorescence microscope. Crab-like fusion cells on leaf surface, intercellular hyphal cells in leaf tissues, as well as nucleus states, were observed and counted up in this study. Under unsaturated humidity, 32% of germinated tubes fused into a distinguishable swollen crab-shaped cell at the merging site, and 10.5% of observed crab-like cells had more than three nuclei. Wedge-shaped mycelia developed and then penetrated the leaf surface directly, or indirectly through stomata. Tips of germtube passed through the intercellular cells of poplar leaves directly were found in TEM. Aniline blue dyeing also showed that the infecting hyphae could invade into the cuticle and epidemic cell wall directly. For the case of infection through stomata, there were two different situations. Short branches and wedge hyphae usually penetrated the leaf surface via opened stomata, whereas, some germtube branches and wedge hyphae penetrated leaves through the guard cell walls or stoma lips. In the latter case, the stomata were always closed. The samples from wild forestlands had the same fused cells and wedge hyphae, but the occurrence rate was much higher than that in the chamber. Even under the saturated air humidity, germtubes could roll back and formed fusion structure, or merged together with their tips. The fusion cells might centralize the plasma of merged germtubes and have a strong survival capacity to protect germtubes from dying under arid circumstances, and provide a chance of genetic variation as well.