Insufficient organic carbon in cropland soil limits heterotrophic denitrification, exacerbating nitrate (NO₃⁻) leaching pollution under high nitrogen fertilization. While maize straw return can enhance denitrification, the quantitative relationship between application rates, denitrification performance, and microbial evolution remains poorly understood. Here, we investigated how varying straw application rates regulate nitrogen transformation and microbial mechanisms through experiments on organic carbon release, denitrification potential, and long-term soil column leaching. Maize straw released up to 419.2 ± 14.4 mg/L of organic carbon within 120 h, whereas soil organic matter contributed minimally, confirming straw as the primary electron donor for NO₃⁻ reduction. Straw-amended soils achieved a denitrification efficiency of 96.8% ± 0.3%, which was 5.1 to 13.5 times higher than that of soil alone. Under long-term leaching, a 1% application rate reduced the NO₃⁻ leaching ratio to 6.9%, and to only 0.85% during stable operation (50–90 d), indicating effective NO₃⁻ interception and removal. However, this effect diminished at higher rates. Microbial analyses revealed that moderate carbon inputs enriched denitrifying taxa, whereas excessive straw favored fermentative populations and destabilized nitrogen transformation. Overall, this study not only deepened the understanding of the mechanisms by which maize straw return regulates soil denitrification and microbial evolution but also provided insights for controlling agricultural non-point source pollution.

This study aimed to investigate the effects of substituting different proportions of chemical fertilizer with organic fer-tilizer on sweet corn yield and soil N2O emission characteristics,so as to provide a theoretical basis for establishing a nitrogen application regime that achieves both high crop yield and environmental friendliness in the oasis irrigation area of Northwest China.A two-year field positioning experiment was conducted at the Wuwei Oasis Agricultural Experimental Station.A conven-tional chemical fertilizer treatment(CK)was used as the control,and four organic fertilizer substitution treatments were set:re-placing 10%,20%,30%,and 40%of chemical fertilizer with organic fertilizer(M1,M2,M3,and M4,respectively).By dynami-cally monitoring soil N2O flux,soil ammonium nitrogen(NH4+-N)and nitrate nitrogen(NO3--N)contents,and the activities of nitrate reductase(NR)and nitrite reductase(NiR).we analyzed the effects of partial substitution of chemical fertilizer with or-ganic fertilizer on soil N2O emissions in sweet corn fields and the underlying mechanisms.Based on the mean results of the two-year experiment,compared with the CK treatment,the M2 treatment significantly increased sweet corn biomass yield and fresh ear yield by 12.57%and 4.51%,respectively,while the M3 and M4 treatments significantly reduced yields.All partial or-ganic fertilizer substitution treatments significantly reduced the peak N2O emissions after basal fertilization and the first topdres-sing,as well as the cumulative N2O emissions during the sweet corn growing season.Compared with CK,the M1,M2,M3,and M4 treatments reduced the global warming potential(GWP)of N2O by 2.52%-8.89%and the emission intensity(EI)by 3.26%-10.35%.Among them,the M3 treatment exhibited the lowest GWP,and the M2 treatment had the lowest EI.Mantel test and random forest model analysis revealed that cumulative soil N2O emissions were extremely significantly positively correlated with NH4+-N and NO3--N contents,as well as NR and NiR activities at the sowing stage,and significantly positively correlated with NO3--N content and NiR activity at the jointing stage.Further analysis using a structural equation model indicated that par-tial substitution of chemical fertilizer with organic fertilizer primarily reduced N2O emissions by decreasing the NH4+-N content at the sowing stage,thereby indirectly affecting NO3--N content and NiR activity.In conclusion,substituting 20%of chemical fer-tilizer with organic fertilizer(M2)ensures increased sweet corn yield while significantly reducing soil N2O emissions,and can be recommended as the optimal fertilization regime for balancing production efficiency and emission reduction goals in the oasis irrigation area.

Limited sample sizes and regional differences in pollution characteristics and soil properties often obscure the characteristic bands of soil heavy metal (SHM), thereby reducing the stability, accuracy, and generalizability of prediction models. These limitations ultimately hinder the engineering application of hyperspectral remote sensing in SHM detection. To overcome this, a Near-standard Soil Spectral Library (NSSL) was innovatively developed by producing near-standard soil samples for cadmium (Cd), lead (Pb), and arsenic (As). Furthermore, the effectiveness of characteristic bands identified from NSSL was assessed through different machine learning models using both laboratory and field in-situ spectra from mining and agricultural scenarios. Additionally, the capability of NSSL as prior spectral knowledge was further examined to enhance the accuracy of prediction models and to improve model transferability. The results indicated the characteristic bands of SHM were identified as 405-501, 769-994, 1130-1142, 1196-1278, 1376-1468, 1670-1782 and 1949-2374 nm for Cd, 409-540, 1813-2060 and 2214-2354 nm for Pb, and 403-578, 1890-1898, 2053-2067, 2263-2266 and 2307-2356 nm for As. As prior spectral knowledge, NSSL significantly improved model accuracy based on field in-situ spectra under limited sample sizes, improving Rv2 values from 0.68 to 0.79 for Cd, from 0.69 to 0.78 for Pb, and from 0.72 to 0.80 for As. The performance (Rv2) of model transferability was enhanced from 0.57 to 0.79 for Cd, from 0.53 to 0.73 for Pb, and from 0.29 to 0.57 for As. These results emphasize the reliability of NSSL in supporting hyperspectral remote sensing for SHM detection and constitute a milestone in advancing the field.

The continuous rise in atmospheric CO₂ concentration and its impact on global climate underscore the urgency of reconciling food security with carbon emission reduction. While leguminous green manure incorporation offers ecological benefits, the synergistic effects of its integration with reduced chemical nitrogen fertilizer application on soil respiration components and underlying mechanisms remain poorly understood. A three-year field experiment (2023 −2025) was conducted in an oasis irrigation area of Northwest China, evaluating five treatments under green manure incorporation: Traditional nitrogen application (N100), nitrogen reduction by 10% (N90), nitrogen reduction by 20% (N80), nitrogen reduction by 30% (N70), and nitrogen reduction by 40% (N60). The results showed that compared with the N100 treatment, the N80, N70, and N60 treatments significantly reduced soil respiration rate (Rs), with reductions ranging from 12.8% to 22.9%, an effect primarily attributed to the suppression of microbial heterotrophic respiration (Rh). In addition, the N80 treatment optimized soil physicochemical properties and increased the relative abundance of key microbial taxa such as Ascomycota and Gemmatimonadota. These synergistic changes provided critical evidence for explaining the observed agricultural carbon mitigation effect. Random forest analysis revealed that soil pH and soil water content (SWC) were key drivers of bacterial communities, while fungal communities were mainly regulated by soil NO₃⁻-N and NH₄⁺-N content. Structural equation modeling (SEM) further confirmed that nitrogen reduction under green manure incorporation affected heterotrophic respiration through a multi-level "physical-chemical-microbial" pathway, ultimately regulating soil respiration intensity. These findings demonstrate that nitrogen reduction by 20% combined with green manure incorporation represents a promising synergistic strategy for reducing soil CO₂ emissions, improving soil fertility, and regulating microbial communities in oasis irrigation agricultural systems.

Water scarcity and high grain yield are the two critical challenges for sustainable agricultural development. An appropriate amount of green manure (GM) incorporation with nitrogen (N) reduction can ensure high and stable crop yields, but it remains unclear whether this approach can enhance soil moisture status and optimize water use characteristics. This study aimed to investigate the effects of different amounts of GM incorporation with N reduction on the grain yield and water use characteristics of wheat. A field experiment was conducted in the arid irrigated area of Northwest China from 2021 to 2023. Seven treatments were established: (i) conventional N application without GM (N100), (ii) 15,000 kg ha- 1 GM + 15 % N reduction (M1N85), (iii) 15,000 kg ha- 1 GM + 30 % N reduction (M1N70), (iv) 22,500 kg ha- 1 GM + 15 % N reduction (M2N85), (v) 22,500 kg ha- 1 GM + 30 % N reduction (M2N70), (vi) 30,000 kg ha- 1 GM + 15 % N reduction (M3N85), and (vii) 30,000 kg ha- 1 GM + 30 % N reduction (M3N70). The results showed that compared with N100, GM incorporation with N reduction had the advantages of increasing soil organic matter (SOM) and total nitrogen (STN) at 0 -120 cm and canopy coverage (CC), root biomass (RB), and dry matter accumulation (DMA) from the anthesis to maturity stage, among which M3N85 had the most significant effect. Meanwhile, this treatment effectively increased soil water storage (SWS) at 0 -120 cm in the three main growth stages (vegetative, concurrent, and reproductive growth stages), reduced soil evaporation (SE) in the three main growth stages, and increased transpiration (T) in the concurrent and reproductive growth stages, finally increasing wheat grain yield (GY) and water productivity (WP) by 28.1 % and 22.7 %, respectively. In addition, structural equation model (SEM) revealed that DMA was the main factor in improving WP. In conclusion, 30,000 kg ha- 1 GM + 15 % N reduction could be an effective agricultural strategy to alleviate the contradiction between high wheat yield and water shortage in this region.

Rice yield remains limited by trade-offs between effective panicle number, grain number per panicle, and grain weight. However, the molecular mechanisms linking auxin transport to panicle formation in rice remain largely unknown. In this study, we conducted genome-wide association studies and identified Suppressor of Effective Panicle 1 (SEP1), which encodes a basic helix-loop-helix transcription factor that negatively regulates effective panicle number and yield. SEP1 directly activates OsPIN1a and OsPIN1b, two auxin efflux carriers that modulate auxin transport and distribution in tiller buds. Natural variation in SEP1 alters the transcriptional activation capacity of SEP1, and the SEP1Hap2 allelic variant exhibits weaker transcriptional activation of OsPIN1a and OsPIN1b, correlating with its prevalence in Xian cultivars with relatively higher panicle numbers. Furthermore, we discovered that Gnp4/LAX PANICLE 2, a RING finger and WD40-associated ubiquitin-like domain-containing protein, destabilizes SEP1 via ubiquitin-proteasome degradation, fine-tuning auxin transport and tiller bud elongation. Notably, knockout of SEP1 in Xian/Geng cultivars significantly increases yield in field trials. Collectively, our study reveals a molecular mechanism for regulating rice yield and provides a practical strategy for breeding high-yield rice.

The growing demand for cereal production has led to increasing agrochemical inputs; therefore, evaluation and adjustment of current practices are required to maintain and improve sustainable cropping systems. A Four-years study of multiple practices with reduced agrochemical application for rice farming was conducted and investigated in southern China to assess impacts on food safety and ecological resilience. A 30 % reduction in total pesticide use resulted in a 20 % decrease in ecological risk to earthworms, primarily due to reduced application of key pesticides: pymetrozine, pretilachlor, difenoconazole, propiconazole, thifluzamide, tricyclazole, and hexaconazole. A 22 % reduction in total mineral fertilizer use had a slight impact on soil fertility; however, certain practices involving partial replacement of chemical fertilizers with organic manure enhanced soil enzyme activity. This improvement was also linked to changes in the soil bacterial community, particularly the enrichment of Gemmatimonadetes, Actinobacteria, and Cyanobacteria, which contributed to enhanced soil fertility. Additionally, reduction in agrochemical application was accompanied by a declining trend in heavy metal accumulation; however, exposure risks of arsenic and Cd still require consideration. Our study demonstrates that progressive reduction of agrochemical inputs can mitigate pollutant risks and reactivate soil self-restoration processes, thereby enabling the design of adaptable sustainable cropping systems with optimized ecological trade-offs.

Panax ginseng as a perennial herb of Araliaceae,exhibits pharmacological effects such as central nervous system stimulation,anti-tumor properties,and cardiovascular and cerebrovascular protection.The B3 gene family plays a crucial role in growth and development,antioxidant activity,stress resistance,and secondary metabolism regulation of plants and has been extensively studied in various plants.However,the identification and analysis of the B3 gene family in P.ginseng have not been reported.In this study,a total of 145 B3 genes(PgB3s)with complete open reading frames(ORF)were identified from P.ginseng and classified into five subfamilies based on domain types.Through correlation analysis with ginsenoside content,SNP/InDels analysis,and interaction analysis with key enzyme genes,15 PgB3 transcripts were found to be significantly correlated with ginsenoside content and exhibited a close interaction network with key enzyme genes involved in ginsenoside biosynthesis,which indicated that these genes may participate in the regulation of ginsenoside biosynthesis.Additionally,this study found that PgB3 genes exhibited induced expression in response to methyl jasmonate(MeJA)stress,which aligned with the presence of abundant stress response elements in their promoters,confirming the important role of the B3 gene family in P.ginseng in stress resistance.The results of this study revealed the potential functions of PgB3 genes in ginsenoside biosynthesis and stress response,providing a significant theoretical basis for further research on the functions of PgB3 genes and their regulatory mechanisms.

Selecting high-yielding rice cultivars with superior quality under a changing climate is of particular importance for ensuring future food security. In this field experiment, japonica rice Wuyunjing27 (WYJ27) and indica rice Yangdao6 (YD6) displaying low and high yield enhancement at elevated CO2 (eCO2), respectively, were compared in their grain quality responses to free-air CO2 enrichment (FACE). Grains located at apical primary rachis (superior spikelets, SS) and at proximal secondary rachis (inferior spikelets, IS) were separately investigated in their responses to eCO2 because of the asynchronous grain development in rice panicles. Significant quality declines were found in SS of WYJ27, including increased chalky grains and decreased protein and amino acid concentration; in contrast, YD6 was less affected by eCO2 in these traits. Grain quality of IS of both cultivars was less affected by eCO2, which might be associated with improved grain ripening, as shown by the reduced proportions of immature grains at harvest. Gel consistency and peak, hot, and final viscosities in the starch rapid visco analyzer profile were increased by eCO2 when averaged across SS and IS of the two cultivars, indicating enhanced stickiness of cooked rice. For nutrient compositions, only grain sulfur concentration was reduced by eCO2, while the concentrations of other mineral elements and phytic acid were unchanged when averaged across SS and IS of the two cultivars. These results indicate that indica rice with higher yield increase from eCO2 displayed less quality deterioration, but the underlying mechanisms need further investigation in order to breed rice with both high yield and good quality in eCO2 environments.

Green manure (GM) incorporation combined with nitrogen reduction can promote crop quality improvement. However, the mechanisms by which GM incorporation combined with nitrogen reduction enhances crop quality remain unclear. This study aimed to investigate the effects of GM incorporation amount combined with nitrogen reduction amount on wheat grain protein (GP) and starch (GS) content, and their mechanisms. A field experiment was carried out in an arid oasis region in northwestern China from 2022 to 2023. The seven treatments were as follows: (i) no GM incorporation + conventional nitrogen application (N-100), (ii) 15,000 kg ha(-1) GM incorporation + 15 % nitrogen reduction (G(1)N(85)), (iii) 22,500 kg ha(-1) GM incorporation + 15 % nitrogen reduction (G(2)N(85)), (iv) 30,000 kg ha(-1) GM incorporation + 15 % nitrogen reduction (G(3)N(85)), (v) 15,000 kg ha(-1) GM incorporation + 30 % nitrogen reduction (G(1)N(70)), (vi) 22,500 kg ha(-1) GM incorporation + 30 % nitrogen reduction (G(2)N(70)) (T), (vii) 30,000 kg ha(-1) GM incorporation + 30 % nitrogen reduction (G(3)N(70)). Results showed that compared with N100, all GM incorporation amount combined with nitrogen reduction amount treatments significantly increased wheat grain yield (GY), nitrogen use efficiency (NUE), GP and GS. Among them, G(3)N(85) exhibited the greatest improvements, enhancing GY by 26.5 %-42.6 %, NUE by 15.4 %-28.9 %, GP by 10.3 %-14.9 %, and GS by 8.1 %-15.5 %. In addition, compared with N-100, the GM incorporation amount combined with nitrogen reduction amount treatments increased soil organic carbon (SOC) and soil mineral nitrogen (SMN), optimized wheat root biomass (RB), flag leaf net photosynthetic rate (P-n), transpiration rate (T-r), and promoted the nitrogen transport and distribution in various organs of wheat, enhancing sucrose phosphate synthase (SPS) activity, sucrose synthase (SS) activity, sucrose content, grain amylopectin content, and amylose content, with G(3)N(85) showing the most significant effects. Structural equation modeling revealed that an increase in wheat RB promoted T-r and activated SS, thereby enhancing GS through the direct synthesis of amylose and sucrose-dependent amylopectin. The increase in GP was attributed to enhanced nitrogen translocation from vegetative organs to the grains and the subsequent rise in grain nitrogen content. Therefore, under the G(3)N(85) treatment, wheat yield can be maintained while simultaneously increasing GP and GS content, making it the optimal approach for combining GM incorporation with nitrogen reduction in arid oasis irrigation areas.

Ozone pollution decreases rice yield and quality in general, but how ozone stress changes grain-filling capacity is unclear. A chamber experiment was conducted to compare the effects of ozone exposure during the rice growth season on the grain-filling capacity and quality of spikelets located on the upper primary rachis (superior spikelets, SS) and the lower secondary rachis (inferior spikelets, IS). Ozone stress significantly decreased filled grain percentage by 41.4% and grain mass by 10.2% in IS, but had little effect on grain-filling capacity in SS. Consistent with the reduction in grain mass, ozone stress decreased grain volume, mainly due to reduced grain thickness, and IS was reduced more than SS. After removing the hull, brown rice obtained from ozone treatment exhibited higher proportions of immature and abnormal kernels, resulting in a substantially lower proportion of perfect kernels. Under ozone stress, the proportion of perfect kernels was only one-third in IS, compared with two-thirds in SS. Ozone stress affected the pasting properties of brown rice for both SS and IS, as shown by the decreased amylose content, and the increased maximum viscosity, minimum viscosity, final viscosity, setback, and peak time of the rapid visco analyzer profile. Out of fourteen traits related to nutritional quality of brown rice, only five showed significant increases under ozone stress, and they were the concentrations of albumin, prolamin, sulfur, copper, and manganese. The differential ozone responses between SS and IS were rather small for rice pasting properties and chemical compositions as shown by very few significant interactions between ozone and grain position. It is concluded that ozone stress during plant growth imposed more adverse effects on IS than SS in terms of grain-filling capacity and appearance quality, suggesting an enlarged asynchronous grain-filling pattern in rice panicles under ozone pollution. Strategies to improve the grain-filling capacity of IS are needed to mitigate ozone-induced damage to rice production.

Wheat-maize rotation is a widely used planting pattern in oasis-irrigated areas in Northwest China. Although this planting pattern has the advantage of breaking the barrier of continuous cropping to some extent, it also presents some problems, such as large evaporation and prominent soil degradation during the fallow period, which seriously restricts the improvement of crop yield. Planting green manure (GM) after wheat and returning it to the field can effectively improve soil physicochemical properties, regulate the photosynthetic characteristics of subsequent crops, and promote crop yield. However, the photosynthetic physiological mechanism of crop yield improvement under different green manure return methods (GMRM) remains unclear. Therefore, by exploring the relationships among soil moisture and temperature environment, maize root structure, photosynthetic characteristics, fluorescence characteristics and yield under different GMRM, this study aims to provide a theoretical basis for clarifying the photosynthetic physiological mechanism of GMRM to improve maize yield. A three-year field experiment was conducted at a research station in the Shiyang River Basin (Gansu, China). Five treatments were involved in this study: (i) conventional tillage without GM (CT), (ii) no-tillage with total GM mulching (NTG), (iii) no-tillage with removal of aboveground GM (NT), (iv) tillage with total GM incorporation (TG), and (v) tillage with only root incorporation (T). Results showed that the NTG and TG significantly increased soil water content (SWC) in 0-110 cm soil layer, soil temperature (ST) of maize seedlings (V3) to jointing stage (V6), canopy cover (CC), leaf stay-greenness (SG), root length (RL), net photosynthetic rate (Pn), transpiration rate (Tr), actual photochemical efficiency of PSII (Phi PSII), maize biomass, and grain yield (GY) compared with CT. In addition, NTG and TG significantly decreased the ST of maize from the big trumpet stage (V12) to the blister stage (R2), and the dissipation of excess energy (NPQ), compared with CT. GM's return to the field could improve root structure and canopy coverage of maize mainly by improving soil water content. The optimization of maize root structure and canopy coverage increased the maize chlorophyll content (SPAD) value and promoted Pn. The increase in Pn inhibits the increase in NPQ, thus promoting the activation of Phi PSII. The increase in Phi PSII promoted the increase in maize biomass, ultimately leading to an increase in maize GY.

Elevated atmospheric CO2 concentration (eCO2) is a key driver of climate change, influencing crop yield and quality. However, its effects on the cooking and eating quality (CEQ) of hybrid rice remain unclear. This study investigates eCO2's effect on CEQ by conducting a field experiment from 2015 to 2017 with three popular varieties grown in a free-air CO2 enrichment platform. eCO2 enhanced the volume and surface area of starch granule due to the formation of additional dents and holes on its surface upon eCO2, thereby altering its morphology and potentially influencing starch-protein interplay. It also induced significant changes in starch molecular structure, including increases in blue value (22.4 %), iodine binding power (5.7 %), and amylose content (5.5 %), while protein concentration decreased. These changes led to improvements in pasting (11.0 % increase in breakdown) and thermal properties (ΔHgel increased by 15.6 %), ultimately enhancing the rice taste by 8.5 %. Statistical analysis indicates that these improvements were primarily driven by eCO2-induced changes in starch granule structure. Indica-hybrid rice exhibited a greater response to eCO2, which was influenced by environmental conditions. This study provides valuable insights into how eCO2 affects hybrid rice CEQ, highlighting the need to consider varietal and environmental factors when developing climate adaptation strategies.

Extruded rice has increasingly gained popularity in the market due to its convenience and acceptable texture. The objective of this study was to understand how the physicochemical, thermal, and textural properties of the extruded rice affected its cooking properties and texture of the cooked one. It was found that air trapped in the grains during extrusion reduced the transparency of extruded rice. More air trapped in the grains reduced the true density of the extruded rice, which in turn decreased the hardness of extruded rice. A looser internal structure of extruded rice grain, as indicated by the lower true density, resulted in a faster hydration and shorter optimum cooking time. Extruded rices showed two thermal-transition peaks, with peak 1 from 93.3 degrees C to 112.8 degrees C and peak 2 from 107.5 degrees C to 132.5 degrees C. The increased hardness of extruded rice led to increases in its thermaltransition temperatures, longer optimum steaming time, and decreases in its water absorption and cooking loss, which resulted in an increase in the hardness and a reduction in the adhesiveness of the steamed one. This study provides insights into the key factors determining the eating quality of extruded rice, which is beneficial for food scientists in developing premium extruded rice.

IntroductionThis study explores how elevated CO2 concentration may alter the source-sink dynamics in rice by providing additional carbon for photosynthesis, thereby affecting nutrient absorption and distribution.MethodsA free-air CO2 enrichment experiment was conducted on a japonica cultivar Wuyunjing 27 in 2017 and 2018 growing seasons. The plants were exposed to ambient and elevated CO2 level (increased by 200 μmol·mol-1) and two source-sink manipulation treatments (control with no leaf cutting and cutting off the top three leaves at heading).ResultsThe elevated CO2 significantly increased the above-ground biomass and the straw non-structural carbohydrate concentration by an average of 19.3% and 12.5%, respectively. Significant changes in the concentrations of N, S, Fe, and Zn in straw were noted under elevated CO2, with average decreases by 7.1, 7.2, 11.6, and 10.1%, respectively. The exposure to elevated CO2 significantly enhanced the elements accumulation, yet it had minimal impact on their distribution across different organs. When compared to intact rice, removing the top three leaves at heading reduced the above-ground biomass by 36.8% and the straw non-structural carbohydrate content by 44.8%. Leaf-cutting generally increased the concentration of elements in stem, leaf, and grain, likely due to a concentration effect from reduced biomass and carbohydrate accumulation. Leaf-cutting reduced element accumulation and shifted element allocation in rice organs. It increased the proportion of elements in stems while reduced their presence in leaves and grains.DiscussionOur study suggests that a dilution effect may cause a decrease in mineral elements concentrations under elevated CO2 because of the increase in biomass and carbohydrates.

IntroductionThe panicle fertilization strategy for japonica and indica rice under wheat straw return (SR) has not been updated, especially on the elaboration of their impacts on spikelet differentiation and degeneration. This study aimed to verify the hypothesis that SR increases spikelet number by reducing spikelet degeneration and to explore the possibility of simplifying panicle fertilization.MethodsIn three consecutive years, four varieties of japonica and indica rice were field-grown in Yangzhou, Jiangsu Province, China. Six panicle fertilization rates and split treatments were applied to SR and no straw return (NR) conditions.ResultsThe results showed that SR promoted rice yield significantly by 3.77%, and the highest yields were obtained under the T2 (split panicle fertilization at the panicle initiation (PI) and spikelet primordium differentiation (SPD) stages) and T1 (panicle fertilization only at the PI stage) treatments, for indica and japonica rice, respectively. Correlation and path analysis revealed that the number of spikelets per panicle was the most attributable to yield variation. SR significantly increased the concentration of alkali hydrolyzable N in the soil 40 days after rice transplantation, significantly increased the nitrogen accumulation per stem (NA) during the SPD-pollen mother cell meiosis (PMC) stage, and increased the brassinosteroids level in the young panicles at the PMC stage. SR also reduced the degeneration rate of spikelets (DRS) and increased the number of surviving spikelets (NSS). The dry matter accumulation per stem was more important to increasing the NA in japonica rice at the PMC stage, whereas NA was more affected by the N content than the dry matter accumulation in indica rice. In japonica rice, panicle N application once only at the PI stage combined with the N released from SR was enough to improve the plant N content, reduce the DRS, and increase the NSS. For indica rice, split application of N panicle fertilization at both the PI and SPD stages was still necessary to achieve a maximum NSS.DiscussionIn conclusion, under wheat SR practice, panicle fertilization could be simplified to once in japonica rice with a significant yield increase, whereas equal splits might still be optimal for indica rice.

Context: Elevated atmospheric CO2 concentration (eCO2) impacts grain yield and quality of rice, but whether grains at different positions on a large panicle of hybrid rice respond differently to eCO2 is unclear. Objective: A 2 -year field experiment was conducted to study eCO2-induced changes in grain yield and quality of hybrid rice, with emphasis on the differences between superior spikelets (SS) and inferior spikelets (IS). Methods: A hybrid indica cultivar YLY900 was exposed to ambient and elevated CO2 (+200 mu mol mol-1) at a large free air CO2 enrichment (FACE) platform in two successive rice seasons. Grain yield, yield components, grain filling capacity and quality traits of SS and IS were measured. Results: Averaged across two years, eCO2 increased grain yield of YLY900 by 15%, which was mainly due to enlarged spikelet density, especially that of secondary branches of panicles. Compared with rice season of 2017, low air temperature, overabundant rainfall and lack of light in the early growth stage in 2016 inhibited tillering formation, resulting in lower panicle density and reduced CO2 fertilization effect on grain yield (22% in 2017 vs. 9% in 2016). In general, grain filling capacity of SS was superior to that of IS, as shown by higher fully -filled grain percentage, larger grain size and grain weight. Grain quality of SS was better than that of IS in terms of less grain chalkiness, fewer green grains, and better cooking quality. However, the concentrations of P, K, Ca, Mg, S and Mn were lower in SS than IS. For both SS and IS, eCO2 decreased head rice percentage, grain N and S concentrations, but increased cooking quality as indicated by the changes in RVA profiles. No grain position by CO2 interactions on grain quality traits were detected except the grain appearance: SS had few green grains at either CO2 condition, but IS had a great portion of green grains, which was reduced by approximately 50% at eCO2. Conclusions: Weather conditions at the key growth stage of sink formation had a strong impact on the CO2 fertilization effect. Although grain quality of SS and IS differed significantly, their responses to CO2 elevation were similar except the eCO2-increased grain ripeness of IS. Implications: Elevated CO2 may not be able to offset the yield loss caused by unfavorable weather conditions for rice growth, a proper adjustment in crop management is needed to improve rice yield and quality in future high CO2 environments.

The projected increase in atmospheric CO2 concentration (CO2) is expected to enhance rice yield, while the temperature increase lowers it. However, how air temperature increase modifies this effect of CO2 fertilization is still unclear, particularly across different ambient temperatures. To investigate this phenomenon, a temperaturefree air CO2 enrichment experiment in paddy field was conducted in 2013 and 2014. An japonica rice (Oryza sativa L.) Wuyunjing 23 was exposed to two levels of CO2 (ambient and elevated by 200 mu mol mol-1 during daytime) in combination with two temperature regimes (ambient and elevated by ca. 1 degrees C during daytime). Elevated CO2 significantly increased grain yield in both seasons, but temperature impacts on the magnitude of CO2 responses differed between two seasons: a significant CO2 x temperature interaction was detected in 2013 (mean air temperature 26.6 degrees C), with 24 % increase in grain yield under ambient temperature vs 8 % under elevated temperature; while in 2014 (mean air temperature 23.6 degrees C), a similar CO2-induced increase under ambient (+12 %) and elevated temperature (+16 %) was detected. Plant height significantly increased upon CO2 elevation in 2014 at various growth stages but not in 2013. The effects of CO2 x temperature interaction on grain yield were primarily attributed to variations in panicle (or tiller) numbers, with negligible effects on other yield components. The aboveground biomass patterns mirrored those of grain yield in the responses to CO2, temperature and their interaction, while less effect of CO2 or temperature treatment was found on harvest index. The results demonstrate that interactions between CO2 and temperature on rice are dependent on growth season temperature: high daytime temperature stress during the early growth period of rice can interfere with tillering formation and lead to less yield gain from CO2 enrichment.

Context or problem: Higher-yield and superior-quality rice are the major goals in rice breeding and nitrogen management. Genetic modification combined with optimal nitrogen (N) fertilization is expected to realize it.Objective or research question: Modification in transaldolase (TAL) expression alters both the number and pattern of vascular bundles in rice plants, but its interactions with N rate remains unknown. Methods: We employed three representative lines with different expression levels of TAL in the same genetic background (Wuyunjing 7, WT), and analyzed their responses in dry matter accumulation (DMA), carbohydrate transport, grain filling, yield, yield components, and grain quality under a wide range of N rate.Results: Increased expression of TAL (OE) promoted rice yield by producing more spikelets per panicle and higher 1000-grain weight, while decreased expression of TAL lowered the seed setting rate and grain weight significantly. Under a fixed N rate, when TAL expression was altered, the direct path coefficients of the seed setting rate and 1000-grain weight to the yield were higher than other yield components, especially at a high N rate. Decreased expression of TAL (RNAi) significantly reduced the starch and non-structural carbohydrates (NSC) contents in the stems, but enhanced the soluble sugar retention, whereas increased expression of TAL enhanced the translocation of NSC. The grain weight at maturity and mean grain-filling rate (mg d-1) increased significantly along with the TAL expression, but their differences among RNAi, WT and OE narrowed at higher N rate. Decreased expression of TAL enhanced the apparent amylose content (ACC) and protein (PC), reduced the starch granule size, and caused a loose starch arrangement and elevated chalkiness, as a consequence, significantly reduced the peak viscosity, hot viscosity, final viscosity, and taste value in a N rate dependent manner. The taste values of OE and WT were similar and the highest value was attained under a moderate N rate.Conclusions: TAL expression plays an important role in the regulation of assimilate supply, grain filling, yield formation, and grain quality. Increased expression of TAL alleviates competition effect among the yield com-ponents and enhances the yield potential, especially under moderate to high N rate. Higher TAL expression combined with a moderate N rate improves ECQ.Implications or significance: TAL expression and N rate interacts to regulate yield components and quality. This finding provides meaningful knowledge to administering N rate and genetically modifying TAL expression in a rice variety.