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Sucrose non-fermenting-1-related protein kinase 1 (SnRK1) plays a key role in rice germination. The small molecule drug, A-769662, activates AMP-activated protein kinase, a mammalian homolog of SnRK1. However, it is unknown whether A-769662 activates SnRK1, thereby affecting germination. SnRK1 in desalted extracts from germinating rice seeds was strongly activated by adding A-769662 in vitro. Applying 50 or 100 μM A-769662 accelerated germination and increased the root length, shoot length, and seedling fresh weight. 50 μM A-769662 treatment increased the catalytic activity and phosphorylation of SnRK1 during germination. Transcriptome analysis and biochemical validation were performed to investigate the mechanism whereby A-769662 treatment promoted rice germination. A-769662 treatment promoted starch hydrolysis by increasing the expression and activity of amylase and inhibited starch biosynthesis by decreasing the expression of OsAGPL2, OsAGPS2a, Wx, and SSIIa. The abscisic acid (ABA) level and gene expression of ABA-induced transcription factors, including OsNF-YC9, OsNF-YC12, OsWRKY24, OsPYL8, OsMKKK62, and OsMKKK63, which reduced the inhibition of germination by ABA were decreased under 50 μM A-769662 treatment. The increased expression of the OsACO3 and OsACO5 genes and increased ethylene levels under A-769662 treatment, which counteracted the inhibition of ABA on germination and, thus, promoted germination. These results demonstrate the activation of A-769662 on SnRK1 and further reveal the regulatory mechanism of A-769662 in rice seed germination and nutrient remobilization.

Powdery Li+-imprinted manganese oxides adsorbent was widely used to the recovery of Li+, but there are some difficulties, such as poor stability in acid solution, inconvenience of operation and separation. In this work, a useful hydrogel composite based H4Mn3.5Ti1.5O12/reduced graphene oxide/polyacrylamide (HMTO-rGO/PAM) was fabricated by thermal initiation method with promising stable, conductive and selective properties. The resulting materials were characterized by field emission scanning electron microscope, infrared absorption spectrum, X-ray diffraction, X-ray photoelectron spectroscopy and electrochemical techniques. The recovery of Li+ was investigated using HMTO-rGO/PAM from brine by a separated two-stage sorption statically and electrically switched ion exchange desorption process. The adsorption capacity of 51.5 mg·g–1 could be achieved with an initial Li+ concentration of 200 mg·L–1 in pH 10, at 45 °C for 12 h. Li+ ions could be quickly desorbed by cyclic voltammetry in pH 3, 0.1 mol·L–1 HCl/NH4Cl accompanying the exchange of Li+ and H+(NH4+) and the transfer of LMTO-rGO/PAM to HMTO-rGO/PAM.

Elevated levels of atmospheric CO2 (eCO2) promote rice growth and increase methane (CH4) emissions from rice paddies, because increased input of plant photosynthate to soil stimulates methanogenic archae. However, temporal trends in the effects of eCO2 on rice growth and CH4 emissions are still unclear. To investigate changes in the effects of eCO2 over time, we conducted a two-season pot experiment in a walk-in growth chamber. Positive effects of eCO2 on rice leaf photosynthetic rate, biomass, and grain yield were similar between growing seasons. However, the effects of eCO2 on CH4 emissions decreased over time. Elevated CO2 increased CH4 emissions by 48%–101% in the first growing season, but only by 28%–30% in the second growing season. We also identified the microbial process underlying the acclimation of CH4 emissions to atmospheric CO2 enrichment: eCO2 stimulated the abundance of methanotrophs more strongly in soils that had been previously exposed to eCO2 than in soils that had not been. These results emphasize the need for long-term eCO2 experiments for accurate predictions of terrestrial feedbacks.

Straw incorporation is a global common practice to improve soil fertility and rice yield. However, the effect of straw incorporation on rice yield stability is still unknown, especially under high fertilization level conditions. Here, we reported the effect of straw returning on rice yield and yield stability under high fertilization levels in the rice–wheat system over nine years. The results showed that straw incorporation did not significantly affect the average rice yield of nine years. Straw incorporation reduced the coefficient of variation of rice yield by 25.8% and increased the sustainable yield index by 8.2%. The rice yield positively correlated with mean photosynthetically active radiation (PAR) of rice growth season and the effects of straw incorporation on rice yield depended on the PAR. Straw incorporation increased the rice yield by 5.4% in the low PAR years, whereas it did not affect the rice yield in the high PAR years. Long-term straw incorporation lowered soil bulk density but improved the soil organic matter, total N, available N, available P, and available K more strongly than straw removal. Our findings suggest that straw incorporation can increase rice yield stability through improving the resistance of rice plant growth to low PAR.

Melatonin mediates multiple physiological processes in plants and is involved in many reactions related to the protection of plants from abiotic stress. In this paper, the effect of melatonin on the antioxidant capacity of rice under salt stress was studied. Melatonin alleviated the inhibition of salt stress on the growth of rice seedlings, mainly by increasing the dry weight and fresh weight of shoots and roots. Melatonin alleviated the membrane damage caused by salt stress, which was mainly manifested by the decrease of TBARS content and the decrease of leaf and root damage. During the whole salt stress period, rice after melatonin pretreatment showed lower ROS (H2O2, O2•−,OH−) accumulation. In the early stage (1–3 d) of stress, the rice after melatonin pretreatment showed a strong increase in antioxidant enzyme activity, while in the later stage (5,7 d), it showed a strong increase in antioxidant content. During the whole period of salt stress, melatonin had a weak regulatory effect on AsA-GSH cycle. Through the above regulation process, the decreasing effect of melatonin on ROS content of rice under salt stress did not decrease with prolonged stress time in a short time (1-7 d). In conclusion, melatonin improved the antioxidant capacity of rice under continuous salt stress, and rice showed variable antioxidant strategies after melatonin pretreatment.

Plant phenomics is a new avenue for linking plant genomics and environmental studies, thereby improving plant breeding and management. Remote sensing techniques have improved high-throughput plant phenotyping. However, the accuracy, efficiency, and applicability of three-dimensional (3D) phenotyping are still challenging, especially in field environments. Light detection and ranging (lidar) provides a powerful new tool for 3D phenotyping with the rapid development of facilities and algorithms. Numerous efforts have been devoted to studying static and dynamic changes of structural and functional phenotypes using lidar in agriculture. These progresses also improve 3D plant modeling across different spatial–temporal scales and disciplines, providing easier and less expensive association with genes and analysis of environmental practices and affords new insights into breeding and management. Beyond agriculture phenotyping, lidar shows great potential in forestry, horticultural, and grass phenotyping. Although lidar has resulted in remarkable improvements in plant phenotyping and modeling, the synthetization of lidar-based phenotyping for breeding and management has not been fully explored. We identify three main challenges in lidar-based phenotyping development: 1) developing low cost, high spatial–temporal, and hyperspectral lidar facilities, 2) moving into multi-dimensional phenotyping with an endeavor to generate new algorithms and models, and 3) embracing open source and big data.

Plant phenomics (PP) has been recognized as a bottleneck in studying the interactions of genomics and environment on plants, limiting the progress of smart breeding and precise cultivation. High-throughput plant phenotyping is challenging owing to the spatio-temporal dynamics of traits. Proximal and remote sensing (PRS) techniques are increasingly used for plant phenotyping because of their advantages in multi-dimensional data acquisition and analysis. Substantial progress of PRS applications in PP has been observed over the last two decades and is analyzed here from an interdisciplinary perspective based on 2972 publications. This progress covers most aspects of PRS application in PP, including patterns of global spatial distribution and temporal dynamics, specific PRS technologies, phenotypic research fields, working environments, species, and traits. Subsequently, we demonstrate how to link PRS to multi-omics studies, including how to achieve multi-dimensional PRS data acquisition and processing, how to systematically integrate all kinds of phenotypic information and derive phenotypic knowledge with biological significance, and how to link PP to multi-omics association analysis. Finally, we identify three future perspectives for PRS-based PP: (1) strengthening the spatial and temporal consistency of PRS data, (2) exploring novel phenotypic traits, and (3) facilitating multi-omics communication.

Relevant evidence of rice quality responses to increased temperatures under field condition has been obtained in our previous study. Understanding the intrinsic mechanism of increased temperatures and fertilizer treatment in regulating rice quality formation will be contributed to the development of mitigation measures suitable for actual field operations and to cope with climate warming. This study investigated the potential role of nitrogen fertilizer in regulating the rice quality under field warming through identifying starch-related property indicators. Results showed application of nitrogen fertilizer at heading stage effectively delayed the significantly increased accumulation of total starch, amylose and amylopectin, and reduced the starch particle size, chain length distribution, and crystal structure induced by high temperature, which further compensated the deterioration of rice quality caused by elevated temperature.

Due to the sensitivity of chalk formation to high temperatures, the global warming will further threaten the improvement of high chalky grain rate in the southern japonica region of China. There have been many studies reported on the role of starch in the formation of chalkiness, but the relationship between nitrogen metabolites and chalkiness has not been given sufficient attention. In this study, we conducted the open field warming experiment and investigated the effects of temperature increase on grain protein metabolism. Results showed under the warming range of predicted global temperature increase (1.9 °C–4.0 °C), field warming apparently accelerated the development of grain endosperm, and the number of protein bodies were increased in both rice varieties, Furthermore, we clarified that the increased temperature regulated the key regulatory factors in protein synthesis and metabolism pathway, and the synthesis, transport, folding, assembly process of grain protein were further affected, and that further lead the component changes of grain storage protein. In conclusion, chalky traits are closely related to the grain storage materials and in this study, increased temperature induced the changes in the accumulation balance of storage proteins, amino acids and starches, which coordinately controls the formation of grain chalkiness.

In the Taihu region of China, overuse of chemical nitrogen (N) fertilizer is often associated with low nitrogen recovery (NRE) and leads to serious groundwater pollution caused by N leaching losses. Controlled-released nitrogen fertilizers (CRNFs) and mechanized deep placement are promising alternatives to broadcasting urea to increase crop yield and NRE in machine-transplanted rice production. However, their interactions with regard to soil N status, N leaching and crop performance are unclear. A two-year (2015 and 2016) field experiment was conducted in a randomized complete block using two fertilization techniques (broadcast and deep placement by mechanical side-dressing fertilization) and three CRNFs (sulphur-coated urea (SCU), polymer-coated urea (PCU) and a bulk blended mixture (BBF)). Conventional high-yield fertilization (four split applications of urea at 216 kg N ha−1 (CK)) and 0–N treatments were established as controls. The results showed that the variation in NH4+-N concentration in the percolation and surface water varied across the different CRNFs, irrespective of the techniques used. NO3− -N concentration in the percolation water varied with water conditions in the field. Deep placement with CRNF correspondingly increased mineral N concentration in percolation at depths of 20 and 60 cm but reduced it in the surface water compared to that of the broadcast, although the benefits varied depending on the CRNF type and growth stage. Deep placement of SCU and PCU significantly increased N leaching and the mineral N in the 40–60 cm soil layer compared to that of the broadcast, due to the intensive N release during tillering and ineffective stage when the rice plant had a weak N uptake capability. Deep placement of SCU had the highest N leaching of 6.65 and 5.34 kg N ha−1 during 2015 and 2016. In contrast, BBF exhibited the lowest N leaching, regardless of fertilization placement, which apparently synchronized N release rates with rice N uptake patterns. In the present study, BBF obtained higher rice yields and N recoveries, without significantly enhancing mineral N leaching losses, when compared to CK. Our results suggest that the use of BBF is a promising alternative to a conventional high-yield fertilization practice, especially if combined with deep placement.

To evaluate the actual and comprehensive response of rice grain quality to global warming in lower reaches of Yangtze River delta, a 3-year open-field warming experiment was conducted with two japonica rice cultivars using Free-air temperature enhancement (FATE) facility. Ningjing3 and Wuyunjing24 were planted under two temperature regimes (NT: natural temperature; ET: elevated temperature) during grain-filling. FATE facility increased rice canopy temperature by 2.7 °C (daytime 1.5 °C/nighttime 3.9 °C), 2.0 °C (daytime 1.6 °C/nighttime 2.5 °C) and 3.4 °C (daytime 2.0 °C/nighttime 4.9 °C) in 2012, 2013 and 2014, respectively. Compared with NT, head rice rate, occurrence of perfect grains, amylose content, setback and consistency were decreased by ET, while occurrence of chalky grains, breakdown, cool paste viscosity, pasting temperature were increased under ET. Response of different chalky types to warming were unstable among cultivars and years. Based on Wu-Gilbert model, we found that the relative activity of starch branching enzyme (SBE) to starch synthase (SS) was decreased by ET, which may contribute to longer average amylopectin chain length. ET increased protein content of rice grain but performed no influence on the relative proportion of amino acids. These results revealed that low-amplitude warming during grain-filling could deteriorate rice milling, appearance and cooking quality, but improved its nutritional quality.

Split fertilization strategy is popularly adopted in rice to synchronize soil nitrogen (N) supply and crop N demand. Attention has been paid more on mid-season topdressing N, but limited on basal N. A clearer understanding of the basal N fate under split fertilization is crucial for determining rational basal N split ratio to improve the yield and reduce the loss to environment. A two-year field experiment with two N rates of 150 and 300 kg N ha−1, two split ratios of basal N, 40% and 25%, and two rice varieties, Wuyunjing 23 (japonica) and Y-liangyou 2 (super hybrid indica), was conducted. Labelled 15N urea was supplied in micro-plots as basal fertilizer to determine the plant uptake, translocation, soil residual, and loss of basal N fertilizer. The results showed that basal N absorbed by rice was only 1.6%–11.5% before tillering fertilization (8–10 d after transplanting), 6.5%–21.4% from tillering fertilization to panicle fertilization, and little (0.1%–4.4%) after panicle fertilization. The recovery efficiency of basal N for the entire rice growth stage was low and ranged from 18.7% to 24.8%, not significantly affected by cultivars or N treatments. Soil residual basal N accounted for 10.3%–36.4% and decreased with increasing total N rate and basal N ratio, regardless of variety and year. 43.8%–70.4% of basal N was lost into the environment based on the N balance. Basal N loss was significantly linearly positive related with the basal N rate and obviously enhanced by the increasing basal N ratio for both varieties in both 2012 and 2013. The N use efficiency and yield was significantly improved when decreasing the basal N ratio from 40% to 25%. The results indicated that the basal N ratio should be reduced, especially with limited N inputs, to improve the yield and reduce the N loss to the environment.

One of the major challenges facing rice breeding is to produce ideotype or ideal plant architecture (IPA) to improve canopy radiation use efficiency and hence grain yield. The hybrid japonica rice Jiayou Zhongke 6 (JYZK-6) is one of the benchmark cultivars with IPA characteristics, but the physio-ecological foundation of its high yield potential is still imperfectly understood. In this study, two-year field experiments were conducted using four japonica rice cultivars including JYZK-6 with contrasting canopy structures. A dynamic canopy light interception simulating device was constructed to capture canopy images representing the diurnal dynamics of solar angles throughout the grain-filling stage. Subsequently, leaf to panicle ratio (LPR), a newly developed physiological trait indicative of source-sink relations, was exploited to quantify the light distribution pattern within the rice canopy. The LPRs with high spatio-temporal resolution clearly showed the diurnal changes of light interception within the rice canopy. Genotypic differences in diurnal pattern of LPR were detected among the tested cultivars in both growing seasons, with the amplitude varying with grain-filling stages. Notably, LPR of the IPA cultivar JYZK-6 and its analogue WYJ-29, had a pattern of a V-shaped graph, peaking at sunrise and sunset while dropping to the lowest at noon during middle and late stages. Morphological measurement showed that the V-shaped pattern was associated with the height difference between flag leaf and panicle, panicle curvature, ratio of leaf area to panicle area, as well as the changing solar angles along with the progression of growth stage. This distinguishing feature of light pattern indicates that within the canopy of IPA cultivars, the leaf receives more light in the morning and afternoon whereas the panicle harvests more light at noon. It is inferred that such novel characteristics may provide the IPA cultivar with advantages of reducing midday suppression over the conventional cultivars, while more work is needed to verify this hypothesis. In summary, findings of this study offer a deeper insight into the physio-ecological processes underpinning radiation use efficiency at canopy level, and hence are valuable for breeding programs for ideotype cultivars.

This study was conducted to investigate the effects of soilless substrates of hydroponically grown long-mat seedlings (HLMS) on seedling quality and field growth characteristics of transplanted super japonica rice. A widely grown conventional super japonica rice cultivar (Wuyunjing 23) was selected as the test material. The effect of HLMS on seedling quality, mechanical transplantation quality, field growth characteristics, yield, and benefit-cost ratio were compared with seedlings grown in organic substrates and traditional nutritive soil, which was selected as the control. Root number, root twisting power and root activity of seedlings cultivated by HLMS were decreased compared to that of the organic substrates and control. However, seedling root length as well as aboveground growth were increased compared to the organic substrates and control seedlings. In the HLMS, the content of gibberellin acid (GA 3 ) decreased while abscisic acid (ABA) content increased compared to that of the organic substrates and control seedlings. During the early stages after transplanting, the re-greening of HLMS was delayed compared to that of the organic substrates and control seedlings. Nevertheless, there were no significant differences in tiller dynamics and crop yield among the HLMS, organic substrates and control treatments. The effects of HLMS on seedling production were similar to those of the organic substrates and traditional nutritive soil in the present study, suggesting that HLMS have the potential to replace traditional nutritive soil in seedling production without decreasing crop yield. Finally, it is important to reduce organic substrates and topsoil dependence during rice seedling production and worthwhile to consider HLMS popularization and its application on a larger scale.

Recently, a novel controlled-release N fertiliser (CRNF) application method using basal CRNF combined with urea top-dressing at the tillering stage has been proposed to enhance rice yield and N use efficiency (NUE). However, its effect on ammonia volatilisation (AV) loss and the yield and NUE of blanket-seedling machine-transplanted rice are unknown. A field experiment was performed to investigate the effect of three types of CRNF (slow-release blending fertiliser (BSRB), polymer-coated urea (PCU) and sulphur-coated urea (SCU)) and two fertilisation regimes (a single basal application (B) and a basal CRNF application combined with urea top-dressing at the tillering stage (BT)) on grain yield, NUE and AV loss from paddy soil of blanket-seedling machine-transplanted rice. Conventional high-yield fertilisation (four split applications of urea at 270 kg N ha −1 (CK)) and 0-N treatments were established as controls. The results demonstrated that the AV flux values from paddy soil varied in distinct patterns for the different CRNF treatments. The cumulative AV loss in the urea treatment during the basal (the first week) and tillering fertiliser (the second week) comprised the majority of the total AV loss, both accounting for 87.2% in each year. Compared with CK, B-BSRB significantly reduced AV loss during the first two weeks and the total AV loss by 24.7% and 27.9% in 2013 and 2014, respectively. B-SCU and B-PCU generally showed no benefits for reducing AV loss relative to urea. Compared with B-PCU and B-SCU, B-BSRB met the N demand of rice, substantially mitigated N loss via AV in paddy fields, and improved yield and NUE of Blanket-seedling Machine-Transplanted rice. The effect of BT for each CRNF on AV loss was not consistent. The BT-BSRB and the BT-SCU correspondingly mitigated AV loss to a certain extent in each year, mostly due to the relatively lower AV loss during the first week, and no significant increase in AV loss at the second week. The BT-BSRB incurred not only the lowest AV loss of 39.7 kg N ha −1 and 37.8 kg N ha −1 but also the highest yield of 11.6 t ha −1 and 10.1 t ha −1 and an NRF of 48.8% and 52.4% in 2013 and 2014, respectively. Our results suggested that combining BSRB and BT optimised rice yield and nitrogen use efficiency while decreasing ammonia volatilization from paddy soil of blanket-seedling machine-transplanted rice.

Storage of non-structural carbohydrates (NSC) in internode parenchyma before anthesis functions as a major carbon source for rice grain filling. In this study, two-year field and pot experiments with three japonica cultivars and two nitrogen (N) fertilization modes were performed, and dynamics of dry matter (DM) in internodes were quantified from 21 day before anthesis (DBA) to 60 day after anthesis (DAA; maturity). Results showed that in comparison to leaves and sheaths, DM in internodes varied dramatically, with a clear pattern of increasing at 21 DBA, peaking at 10 DAA, then dramatically dropping until 20 or 30 DAA, and finally refilling at maturity. The sharp reduction of dry matter in the internodes corresponded with the fastest rate of grain filling, indicating the importance of internode reserves for yield formation. On the other hand, the high rate of refilling in internodes at late stage implies the excess production of leaf photosynthetic assimilates. Similarly, starch content in internodes showed a pattern of decreasing at 20–30 DAA. To clarify the indicative meaning of internode reserves, we calculated their remobilization rate at 20 DAA and refilling rate at 60 DAA. Genotypic variations existed for the three cultivars, with a range of 15.17 %–36.37 % for remobilization rate and 54.36 %–104.33 % for refilling rates in 2018. Overall, N topdressing significantly increased the translocation of internode reserves for all three cultivars. Furthermore, our calculation showed that only about 10 % of the grain yield was formed during the second month of rice grain filling, indicating this period is less important for grain yield. Our findings help to clarify the significance of internode DM dynamics for rice management and should be beneficial to enhance our knowledge of source and sink relations, the fundamental component of crop yield formation.

Salinity stress is one of the most serious factors limiting the productivity of crops. Rice at the seedling stage is extremely sensitive to salt. Studies have shown that melatonin can improve plant resistance to a variety of abiotic stresses, including salt stress. In this study, the mechanism of melatonin in regulating Na+/K+ homeostasis in rice seedlings was explored. The results showed that melatonin pretreatment increased rice dry weight and salt tolerance indices under salt stress. This is because melatonin inhibited the increase of Na+ content and the decrease of K+ content induced by salt stress and increased the ratio of K+/Na+. Melatonin increased the selective absorption indices of rice under salt stress, which indicated that melatonin pretreatment improved the ability of rice to absorb K+ and exclude Na+. The results of root Na+/K+ flux also confirmed this point. Rice pretreated with melatonin showed stronger roots Na+ efflux and K+ influx after salt stress. As signaling molecules, the content of nitric oxide increased in the roots of rice pretreated with melatonin, but the content of hydrogen peroxide decreased. Rice roots Na+/K+ transporters pretreated with melatonin were more sensitive to nitric oxide and hydrogen peroxide, which manifested as the Na+ efflux and K+ influx were stronger after being shocked by nitric oxide and hydrogen peroxide. This was due to melatonin pretreatment increasing roots’ ATP content and H+-pump activity. These results indicated that exogenous melatonin could improve root Na+/K+ transporters' response to reactive oxygen species/reactive nitrogen species as well as increase ATP content and H+-pump activity to maintain Na+/K+ homeostasis in rice under salt stress.

Rice (Oryza sativa L.) productivity is greatly affected by soil salinity and melatonin (MLT) has long been recognized as a positive molecule that can alleviate the damage caused by salt. Here, the role of nitric oxide (NO) in the regulation of salt tolerance by MLT was investigated in rice. MLT pretreatment increased the fresh and dry weight of rice seedlings under salt stress. Its beneficial effects include less relative electrolyte leakage (REL) and better K+/Na+ homeostasis. MLT increased the activity of nitric oxide synthase (NOS). The polyamines (PAs) content and the utilization of arginine were also increased, thereby increasing NO content in salt-stressed rice seedlings. Pharmacological approach showed that NO, as a necessary downstream signaling molecule, was involved in the regulation of MLT on the K+/Na+ homeostasis of rice. Under salt stress, MLT improved the H+-pumps activities in plasma membrane (PM) and vacuole membrane (VM) in roots, MLT also increased the ATP content of rice roots by increasing the NO content of rice. Thus, the efflux of Na+ and the influx of K+ were promoted. When endogenous NO was scavenged, the regulation of K+/Na+ homeostasis by MLT was blocked. Therefore, MLT mediated K+/Na+ homeostasis of rice under salt stress by mediating NO.

Rice (Oryza sativa L.) and wheat (Triticum aestivum L.) are two stable food crops that play a vital role in national food security. Summer rice-winter wheat double-cropping rotation is the dominant crop rotation practice used in the middle-lower Yangtze River region of China. However, excessive application of nitrogen (N) fertilizer in this region has led to low nitrogen use efficiency (NUE). To our knowledge, no studies have investigated the effects of reducing N fertilizer applications during both the rice and wheat seasons on crop yield, NUE, and soil fertility. In this study, we conducted a two-year field experiment using N fertilizer rates of 180, 240, and 300 kg N ha−1 during the rice growing season and 135, 180, and 225 kg N ha−1 during the wheat growing season. No differences in yield were observed among the treatments during the rice growing season; however, reduced N fertilizer application significantly affected yield during the wheat growing season. Reducing the amount of N fertilizer applied during the previous season and current season and the interactions between these seasons (R × W) had no effect on rice yield but did affect wheat yield. In addition, the N application rates significantly influenced N uptake and NUE. During the rice growing season, the N agronomic efficiency (NAE), N physiological efficiency (NPE), N partial factor productivity (NPF), and N recovery efficiency (NRE) increased by 20.6–42.5%, 11.1–15.8%, 23.9–40.2%, and 4.8–28.2%, respectively. During the wheat growing season, the NAE, NPE, NPF, and NRE increased by 20.4–54.9%, 8.2–16.5%, 21.8–58.3%, and 11.6–24.4%, respectively. We applied 15N-labelled urea in the remainder of the soil N fertilization treatments, which indicated that the addition of 15N fertilizer resulted in no difference in the 0–60 cm soil profile after rice harvest. Collectively, reducing N fertilizer application rates can effectively improve NUE and decrease N losses, and short-term reductions in N fertilizer application do not affect soil fertility.

This study investigated the chain length distribution (CLD) of two japonica rice cultivars under six nitrogen (N) treatments by high performance size exclusion chromatography, with the aims to elucidate the effect of N on rice quality and its biological mechanism. Results showed significant influence of N on CLD. In comparison with low N rate, high N lowered the percentage of short amylopectin branches. Fitting with the CLD model of Wu-Gilbert, it suggested that relative activity of SBE to SS was lower at high N rate, thus producing fewer short amylopectin branches. Comparison of CLD between N rates and between cultivars revealed that decrease in short amylopectin branches or the relative ratio of short to long amylopcetin branches correlated with increase in flour gelatinization temperatures (To, Tp, and Tc) and decrease in pasting values (except PaT) and amylose-lipid gelatinization temperatures. In addition, quality traits of Wuyujing3, a cultivar with premium eating quality, expressed stably across N treatments compared with the high-yielding cultivar Wuyunjing7.

Using white-belly and white-core mutants of a japonica rice cultivar Wuyujing3, this study was conducted to compare the physicochemical properties of grains differing in chalkiness type. Chalky grains were larger in length, width, and thickness than the translucent grains, and consequently had higher weight. The notable differences were observed for chemical compositions, with chalky grains showing lower contents of starch and protein than the translucent. Similar trends were noted in the majority of the 17 amino acids examined and contents of manganese (Mn), potassium (K) and magnesium (Mg), suggesting the important role of storage compounds in chalkiness formation. White-belly grains differed from white-core grains in chemical components, with the former having higher amylose contents and lower Zn content. Additionally, white-core grains exhibited markedly lower contents of amino acids derived from oxaloacetate and phosphoenolpyruvate like phenylalanine, aspartate and threonine. However, no noticeable differences were detected between white-belly and translucent grains. Our results indicate different underlying mechanisms of white-belly and white-core, suggesting the necessity of comparing white-belly and white-core in the studies on chalkiness. In addition, future study should focus on interpreting the active role of protein accumulation in chalkiness formation from perspective of interactions of carbon and nitrogen metabolism.

Lodging is an important factor limiting rice yield and quality by bending or breaking stem in japonica rice ( Oryza sativa L.) production. The objectives of this study were to determine the mechanism of lodging resistance in japonica rice as affected by carbohydrate components, especially its related arrangement in culm tissue and response to top-dressing nitrogen (N) fertilizer. Field experiments were conducted in Danyang County, Jiangsu Province, China, by using two japonica rice varieties Wuyunjing 23 (lodging-resistance variety) and W3668 (lodging-susceptible variety) with three top-dressing N fertilizer rates (0, 135 and 270 kg N ha −1 ) in 2013 and 2014. Lodging related physical parameters, morphological characteristics and stem carbohydrate components were investigated at 30 d after full heading stage. Results showed that with increasing N fertilizer rates, the lodging rate and lodging index increased rapidly primarily due to significant reduction of breaking strength in two japonica rice varieties. Correlation analysis revealed that breaking strength was significantly and positively correlated with bending stress, but negatively correlated with section modulus, except for significant correlation at W3668 in 2014. Higher stem plumpness status and structural carbohydrate contents significantly enhanced stem stiffness, despite of lower non-structural carbohydrate. With higher N fertilizer rate, the culm wall thickness was almost identical, and culm diameter increased slightly. The structural carbohydrates, especially for lignin content in culm, reduced significantly under high N rate. Further histochemical staining analysis revealed that high N treatments decreased the lignin deposition rapidly in the sclerenchyma cells of mechanical tissue, large vascular bundle and small vascular bundle region, which were consistent with reduction of bending stress, especially for W3668 and thus, resulted in poor stem strength and higher lodging index. These results suggested that structural carbohydrate plays a vital role for improving stem strength in japonica rice. N rate decreased lodging resistance primarily due to poor stem stiffness, by reducing structural carbohydrate content and lignin deposition in the secondary cell wall of lower internode culm tissue.

To optimize both grain yield and quality of low-glutelin rice cultivars under N-fertilizer strategies, two-year field experiments involving three low-glutelin rice cultivars (W1240, W1721, W025) and an ordinary rice cultivar (H9405) with five N treatments were carried out to determine the effects of N application rate and genotype on protein fractions contents and Glutelin/Prolamin ratio (Glu/Pro). The difference of protein fraction concentrations affected by N application rate existed in genotypes. Ordinary rice cultivar had a larger increase in glutlein concentration affected by N application rate than low-glutelin rice cultivars did. Glutelin in H9405 had a increase of 30.6 and 41.0% under the N4 treatment (360 kg N ha–1) when compared with N0 treatment (no fertilizer N) in 2010 and 2011 respectively, while all the low-glutelin rice cultivars showed relatively smaller increases for two years. Variance analysis showed no significant effect of N application rate on glutelin in W1240 and W025 while the effects on albumin, globulin and prolamin were significant in low-glutelin rice. What's more, N treatment had no significant influence on Glu/Pro ratios in low-glutelin rice cultivars while a significant increase in Glu/Pro ratio was observed in ordinary rice cultivar. So low-gultelin rice cultivars showed a different pattern from ordinary rice cultivars when influenced by N application rate.

The effects of four levels of panicle nitrogen fertilizer on the grain filling characteristics of three rice ( Oryza sativa L.) varieties (super japonica rice Ningjing 3, three-line japonica hybrid rice Changyou 3 and three-line indica–japonica hybrid rice Yongyou 12) were analyzed. The results showed that difference in time of maximum filling rate ( T max ) was the smallest between the superior and inferior spikelets of Ningjing 3, bigger between those of Changyou 3, the biggest between those of Yongyou 12. Ningjing 3 was of the synchronous grain-filling type, Yongyou 12 the asynchronous type, and the Changyou 3 the medium type. The grain filling rate, the initial filling power ( R 0 ), the maximum filling rate ( G max ), and the average filling rate ( G ) of the superior and inferior spikelets of the three varieties under the treatment of panicle N with the amount of 120 kg ha −1 (middle panicle N, shortened as NM) treatment were higher than those of other treatments. NM treatment led to the highest increase in grain weight at the middle stage of filling for all the three varieties. The treatment shortened the early and late stages of grain filling, but extended the middle stage when the filling rate was the highest. However, the middle stage of grain filling of Changyou 3 and Yongyou 12 was much more extended than that of Ningjing 3, indicating a better effect of N on hybrid rice varieties.

Heat induces spikelet sterility during flowering in rice. Spikelet sterility in heat-stressed plants is associated with poor pollination due to insufficient pollen grain deposition and unsatisfactory fertilization from reduced pollen germination on the stigma. Measures aimed at facilitating pollen shedding and pollen germination will help to address the adverse effects of heat stress on spikelet fertility in rice during the flowering stage. Intensified pollination by artificially assisted pollen shedding combined with intensified fertilization by promoting pollen germination through chemical application (pH=8.0, 10 % sucrose, 0.1 mM spermidine, 0.01 % myo-inositol, 0.01 % boric acid, 1 μM 24-epibrassinolide, 1 mM KCl, 1 mM CaNO3, 1 mM CaCl2, 0.03 % casein enzymatic hydrolysate, 0.01 % ferric ammonium citrate, 10 mM γ-aminobutyric acid, and 1–2 drops of Tween 20) increased spikelet fertility significantly compared with that without intensified measures under heat treatments in controlled greenhouse conditions. Intensified pollination increased the percentage of anther dehiscence and the number of pollen grains on the stigma, and the chemical application increased the number of germinated pollen grains on the stigma, thus increasing the spikelet fertility and ultimately the grain yield. In open-field conditions, intensified pollination and fertilization measures increased the spikelet fertility, grain weight and quality significantly under elevated temperatures. The proposed methods of enhancing pollination and fertilization are simple and effective for ameliorating the adverse effects of heat stress on the grain yield and quality in rice. This study provides strategies for sustainable rice production under the high temperatures expected with future global warming.

Background The impact of aging on cerebrovascular function and tissue oxygenation during graded hypoxemia is incompletely known. This study compared the age effect on these variables during cyclic hypoxemia-reoxygenation. Methods Hypoxia-induced changes in arterial (SaO2) and cerebral tissue (ScO2) O2 saturation, middle cerebral arterial flow velocity (VMCA), estimated cerebral vascular conductance (CVC), heart rate (HR) and ventilation were compared between 12 elderly (71 ± 2 yr, 7 women) and 13 young (24 ± 3 yr, 5 women) adults during the first and fifth 5-min exposures to 10% O2. Results Although pre-hypoxia SaO2 did not differ between the groups, ScO2 was lower (P Conclusions The elderly adults safely tolerated cyclic, moderate hypoxemia which lowered SaO2 by 20–25%, despite dampening of cerebrovascular and cardiac responses to hypoxemia.

Background and aims The main objectives of this paper were to investigate the absorption and utilization of nitrogen applied at the panicle stage in rice for promoting and protecting spikelet and the effect of residual nitrogen on the utilization of nitrogen in the succeeding wheat crop in the rotation system. Methods A field experiment was combined with a mini-plot experiment with 15 N labelled urea applied at the panicle stage in rice. The experiments included three nutrient management treatments: F, S1 and S2. 126 kg N ha −1 , 120 kg N ha −1 , 72 kg N ha −1 labeled with 30 atom% excess 15 N were applied in rice, respectively. Results (1) Compare to conventional fertilizer management (F), the optimized fertilizer management (S1&S2) reduced the amount of nitrogen applications, whereas the rice and wheat yield did not decrease, and nitrogen use efficiency was improved. (2) At rice harvest, 4.7–10.7% of the fertilizer 15 N was found in the 0–20 cm profile. The fertilizer 15 N absorbed by the wheat during the period from jointing to heading accounted for 37.0%-51.1% of the total 15 N absorbed. (3) The sum of the ratio of nitrogen absorption from the rice panicle fertilizer applied to the crops (rice and wheat) and ratio of soil residue nitrogen in the wheat field were ordered S2 > S1 > F. Conclusion The optimized fertilization management reduced the loss of the rice nitrogen in the rice–wheat rotation system through improved recycling of rice panicle nitrogen applied in the crop-soil system.

The main objectives of this paper were to explore effective ways of improving the lodging resistance of high-yield rice populations and the lodging resistance capacity responses of different rice populations to nitrogen. Field experiments were conducted at the following two eco-sites: Taoyuan (a special high-yield eco-site) in Yunnan province and Danyang (representative eco-site of the middle and lower Yangtze) in Jiangsu province, China in 2011 and 2012. A super indica hybrid rice called ‘Y Liangyou 2’ was grown at each eco-site under different N levels. The lodging index at Taoyuan was significant lower than that at Danyang. The heavier dry weight per cm of leaf sheath and higher proportion of cellulose and lignin in the basal stems enhanced the stem strengths at Taoyuan, in spite of the smaller culm diameter and thinner wall thickness. The shorter elongated internodes of the basal stems were responsible for the lower plant height and the height of center of gravity. In addition, the lodging index at Taoyuan was affected significantly by nitrogen. With increasing nitrogen, the plant height, the height of the center of gravity, dry weight per centimeter (cm) of basal stems (culms and leaf sheaths), bending stress and carbohydrate content were more susceptible to nitrogen. At Danyang, the responses of morphological and physiological parameters to nitrogen tended to level off, the lodging resistance was primarily related to the morphological characteristics of the basal stem. These results suggested that an improvement in the lodging resistance of high-yield rice populations could be achieved by the suitable plant height with the optimum configuration of internodes, namely, shorter basal stems and a longer peduncle, and by increasing stem stiffness, which was primarily attributed to higher proportions of structural carbohydrates (e.g., cellulose and lignin) and greater plumpness of the leaf sheaths.

Rice production is challenged by asymmetric rise in day and night temperatures. Efforts are required to improve our understanding about the impact of climate change induced asymmetrical fluctuations in temperature extremes. This paper presents first effort to investigate effect of post-anthesis asymmetric daytime, nighttime and diel warming, as predicted under low emission scenario (B1) of Intergovernmental Panel on Climate Change (IPCC), on yield and milling quality of two indica rice hybrids, Teyou-559 (susceptible) and Shanyou-63 (resistant), differing in response to temperature. Four canopy warming regimes, ambient reference (AT), daytime warming (HDT, +1.3 °C), nighttime warming (HNT, +2.7 °C), and diel warming (HDNT, +1.3/2.7 °C), were imposed through free-air temperature enhancement (FATE) facility using infrared heaters. Both hybrids responded differentially to daytime, nighttime and diel warming and shortened grain filling duration (1–2 days), reduced grain yield and 1000-grain weight were determined. Nighttime warming caused more deleterious impact than daytime or diel warming. These results indicate that the daytime (−4%), nighttime (−7%) and diel (−6%) warming under low emission scenario will have differential effects on rice production. This reduction is mainly due to differential decrease in grain weight. Resistant Shanyou-63 proved to be more susceptible to daytime warming, while susceptible Teyou-559 was affected more by nighttime and diel warming. Diel warming had significantly negative influence on head rice recovery of both cultivars, with slight inter-annual variation, followed by nighttime and daytime warming. Reduction in head rice recovery indicated the breakage of rice kernels. Daytime warming had greater effect on grain yield 1000-grain weight than nighttime warming considering per 1 °C warming. Effect of warming on yield and quality can be attributed to reduction in translocation of photosynthates during grain filling, resulting in reduced grain filling, grain weight and development of chalky kernels. Further studies are required to elucidate mechanism underlying differential response to asymmetric warming and to suggest appropriate management practices to minimize yield loses.

This study was carried out to explore the molecular mechanism for down-regulation of TRPC6 expression in the reactive oxygen species (ROS)/PKC signaling in kidney cells. In cultured human mesangial cells, H2O2 and TNF-α inhibited TRPC6 mRNA expression in a time-dependent manner. Inhibition of NF-κB reversed both H2O2- and phorbol 12-myristate 13-acetate (PMA)-induced decrease in TRPC6 protein expression. Activation of NF-κB by knocking down IκBα using siRNA could mimic the suppressive effect of ROS/PKC on TRPC6. a Ca(2+) imaging study showed that activation and inhibition of NF-κB significantly decreased and increased the TRPC6-mediated Ca(2+) entry, respectively. Further experiments showed that PMA, but not its inactive analog 4α-phorbol 12, 13-didecanoate (4α-PDD), caused phosphorylation of IκBα and stimulated the nuclear translocation of NF-κB p50 and p65 subunits. The PMA-dependent IκBα phosphorylation was significantly inhibited by Gö6976. Electrophoretic mobility shift assay revealed that PMA stimulated DNA binding activity of NF-κB. Furthermore, specific knockdown of p65, but not p50, prevented an H2O2 inhibitory effect on TRPC6 protein expression, suggesting p65 as a predominant NF-κB subunit repressing TRPC6. In agreement with a major role of p65, chromatin immunoprecipitation assays showed that PMA treatment induced p65 binding to the TRPC6 promoter. Moreover, PMA treatment increased the association of p65 with histone deacetylase (HDAC) and decreased histone acetylation at the TRPC6 promoter. Consistently, knockdown of HDAC2 by siRNA or inhibition of HDAC with trichostatin A prevented a H2O2-induced decrease in TRPC6 mRNA and protein expressions, respectively. Taken together, our findings imply an important role of NF-κB in a negative regulation of TRPC6 expression at the gene transcription level in kidney cells.

Bardoxolone methyl, a synthetic triterpenoid, improves the estimated glomerular filtration rate (GFR) in patients with chronic kidney disease and type 2 diabetes. Since the contractile activity of mesangial cells may influence glomerular filtration, we evaluated the effect of the synthetic triterpenoid RTA 405, with structural similarity to bardoxolone methyl, on GFR in rats and on mesangial cell contractility in freshly isolated glomeruli. In rats, RTA 405 increased basal GFR, assessed by inulin clearance, and attenuated the angiotensin II–induced decline in GFR. RTA 405 increased the filtration fraction, but did not affect arterial blood pressure or renal plasma flow. Glomeruli from RTA 405–treated rats were resistant to angiotensin II–induced volume reduction ex vivo . In cultured mesangial cells, angiotensin II–stimulated contraction was attenuated by RTA 405, in a dose- and time-dependent fashion. Further, Nrf2-targeted gene transcription (regulates antioxidant, anti-inflammatory, and cytoprotective responses) in mesangial cells was associated with decreased basal and reduced angiotensin II–stimulated hydrogen peroxide and calcium ion levels. These mechanisms contribute to the GFR increase that occurs following treatment with RTA 405 in rats and may underlie the effect of bardoxolone methyl on the estimated GFR in patients.

The objective of this study was to understand the relationship between cooking quality and lipid content and components in milled rice of different cultivars, and the regulation of nitrogen on lipid quality in japonica rice (Oryza sativa L.). Under 7 nitrogen conditions with 4 total nitrogen levels and 2 split ratios, the RVA parameters and contents of crude lipid, lipid components, and amylose were assayed in 6 cultivars. Genotype significantly affected the content and components of lipid in milled rice. The milled rice of small-panicle cultivars had higher contents of crude lipid and starch lipid and lower non-starch lipid in milled rice than that of the large-panicle cultivars. The effect of nitrogen on lipid content and components in milled rice was smaller than that of genotype, and varied among genotypes. The content of crude lipid was significantly and negatively correlated with breakdown value, and the content of starch lipid was significantly and negatively correlated with amylose content, setback value, and consistency viscosity. The results indicate that rice cooking quality can be promoted through cultivar improvement aiming at increasing starch lipid content in milled rice.

Grain filling, a crucial stage of grain yield formation in rice, is usually affected by the panicle nitrogen (N) fertilization. Field and pot culture experiments were conducted to explore the underlying mechanisms of N effect. Two rice cultivars with high lodging resistance were grown in the field and pot. Four panicle N fertilization treatments were conducted in 2006 and repeated in 2007. The result showed that medium level of panicle N fertilization treatment (NM) enhanced the accumulation and translocation of non-structural carbohydrate (NSC) in the stem and sheath. Compared with non-nitrogen treatment (N0), NM promoted the translocation of labeled 13C from stem and sheath to grain. But, low level of panicle N fertilization treatment (NL) and high level of panicle N fertilization treatment (NH) showed the negative effect. The endosperm cell, grain length, and grain width of NM increased more quickly than that of N0 from 4 to 10 d after anthesis. During the early period of grain filling, sucrose-phosphate synthase (EC 2.4.1.14, SPS) activity were significantly higher for the NM treatment than those of the NL and NH treatments. Sucrose synthase (EC 2.4.1.13, SuSase) activity in the grains was substantially enhanced by NM, with the duration of higher activity being longer than those of the other treatments. At maturing stage, NM significantly increased the filled grain number, the seed-setting rate, and the grain weight compared with NL and NH. The results suggest that NM have a positive effect on the activities of enzymes of physiological importance, thereby increasing the grain size and promoting grain filling.

Thirty-one japonica cultivars with contrasting agronomic traits were used and 5 nitrogen (N) fertilizer treatments of level and timing were performed to determine the effects of N application on grain phytic acid and proteins including albumin, globulin, prolamin, and glutelin. Variance analysis showed a large effect of N and a smaller effect of cultivar on grain phytic acid and proteins. With increased N level, grain phytic acid concentrations progressively reduced whereas concentrations of the 4 proteins and ratios of glutelin to total protein increased, indicating that N level has a beneficial effect on rice nutritional quality. In addition, substantial genotypic differences in response of grain phytic acid and proteins to N treatments were detected. Some cultivars such as Xiushui09, Zhendao10, and Yanjing5 exhibited more stability of grain proteins under contrasting N treatments, and the significance of this stability is discussed in regard to its use in rice quality improvement.

A number of field studies have reported very high rice yields in Taoyuan, Yunnan province, China, and the physiological and ecological factors associated with high yield have been explored. However, little attention has been paid to differences in plant type. The main objective of this study was to reveal the plant type characteristics associated with the high rice yield through the comparison of two sites: Taoyuan, Yunnan province and Nanjing, Jiangsu province, China. The physiological and environmental factors were also discussed. Field experiments were conducted at two sites in 2006 and 2007. Three Indica F 1 hybrid varieties, Eryou 107, Xieyou 107 and Eryouhang 1 in 2006, Eryou 107 and Xieyou 107 in 2007 were grown at two sites under optimum crop management to achieve maximum attainable yields. Leaf area, leaf length, leaf width, leaf angles, specific leaf weight (SLW) and specific leaf nitrogen (SLN) at heading, yield and yield components at maturity were determined. Daily radiation, air temperature and relative humidity (RH) were monitored. The highest yield of 18.5 t ha −1 was achieved by Eryou 107 at Taoyuan in 2006, and average yield of all varieties at Taoyuan was 96% and 85% higher than Nanjing in 2006 and 2007, respectively. The higher yield at Taoyuan was attributed primarily to the larger sink size, which was mainly caused by the greater number of panicles per m 2 . Biomass production was greater at Taoyuan than at Nanjing in 2006 and 2007, while differences in harvest index were very small. Compared with Nanjing, the rice planted in Taoyuan has greater leaf area index about 10 with smaller area per stem, shorter, wider and thicker leaves and smaller leaf angles. These results indicate that in addition to the higher biomass accumulation (main physiological factor) and the intense solar radiation with the large diurnal temperature range (main environmental factor), the greater leaf area index (LAI) with smaller area per stem, may be an important morphological factor contributing to the high yield in Taoyuan.

Based on the experiment of measuring panicles and leaves, air temperature, and humidity above the canopy of rice cultivars after heading in 2005 and 2006, we investigated the temperature difference (TD) between the air and organs of rice plant and its relationship with spikelet fertility. The results showed that TDs between the air and organs of rice varied with air temperature, air humidity, and plant type. For similar air humidity, TDs were lower at the air temperature of 28.5℃ than at higher temperature of 35.5℃, whereas for the same air temperature, the TDs decreased as the air humidity increased. TDs were also affected by plant type of the cultivars. Erect panicle cultivars showed higher TDs than those with droopy panicles under similar climatic conditions, and cultivars with panicles above flag leaf (PAFL) had higher TDs than those with panicles below the flag leaf (PBFL). Cultivars grown in a location with lower air humidity and higher temperature, such as Taoyuan, China, had higher spikelet fertility than those in higher humidity under the similar air temperature during the grain filling stage. This is partially attributed to the larger TDs under the lower humidity. Row- spacing and the ratio of basal-tillering to panicle-spikelet fertilizer showed a significant influence on TD and subsequently on spikelet fertility, suggesting the possibility of increasing spikelet fertility by agronomic management.

Summary Background Cardiac complications have been demonstrated as a major cause of morbidity and mortality in the diabetic population. However, the mechanisms underlying diabetes-induced cardiomyopathy remain unclear. We tested the hypothesis that endothelin-1 (ET-1) plays an important role in diabetes-induced pathogenesis of ventricular myocyte dysfunction. Methods Diabetic rat was induced by an intravenous injection of streptozotocin (STZ). The potential contribution of endothelin to diabetic cardiomyopathy was determined by chronic treatment of rats with the ET-1 receptor antagonist, bosentan. Myocyte contractility and intracellular calcium homeostasis were compared using an edge detection/micro-fluorescent system. Results Ventricular myocytes isolated from diabetic rats exhibited significant depression in cell contractility and altered intracellular Ca2+ ([Ca2+]i) transient. On the other hand, L-type Ca2+ channel activity in diabetic myocytes was not altered. Bosentan treatment successfully prevented myocyte contractile dysfunction and [Ca2+]i depression in diabetic rats without affecting myocyte function from control rats. Bosentan had no effect on Ca2+ channel activity in myocytes obtained from both control and diabetic rats. Conclusion These data demonstrate that elevated ET-1 in diabetic animals plays an important role in the diabetes-induced cardiac myocyte dysfunction. Blockade of ET-1 receptor may be a potential therapeutic strategy in the treatment of diabetes-induced heart failure.