BACKGROUND:Early indica rice frequently encounters high temperature damage during grain-filling period in the Yangtze River basin, China induced by later sowing date, decreasing grain yield and qualities. Nitrogen panicle fertilizer application (NPF) positively mitigates the adverse effects; however, the specific details remain unclear. A field experiment using poor or high-quality early indica rice cultivars was conducted over 2 years to investigate rice yield, grain qualities and starch related traits subjected to slightly natural warming (W) under different NPF levels (Low NPF, LN; Middle NPF, MN; High NPF, HN) through delaying sowing date, with normal sowing date as the control. RESULTS:The result showed that under W, compared to LN, elevated NPF (HN and MN) significantly increased the grain yield of the rice cultivars by 11.7-21.0%, which was mainly attributed to the high effective panicle and spikelets. Elevated NPF increased the protein and amino acid contents, especially for the HN treatment, resulting in the high nutritional qualities of rice grain, at the same time as demonstrating increased hardness and stickiness, as well as decreased breakdown and amylose content, negatively affecting the eating and textural qualituies of cooking rice. Notably, compared with HN and LN, MN treatment totally enhanced the processing qualities under W in 2 years. However, HN significantly deteriorated the rice appearance qualities in the temperature treatments. These results might be a result of the unordered arrangement and irregular surface of starch granules, particular high-quality rice cultivar. CONCLUSION:The results suggest that optimizing NPF under slightly warming at grain-filling stage synergistically improve grain yield and processing qualities of early indica rice. © 2026 Society of Chemical Industry.

[Objective]Long-term direct returning of straw to the field improves the physical and chemical properties of the soil and is conducive to soil carbon and nitrogen retention.However,there are differences among various soil layers.This study aimed to clarify the variation characteristics of soil organic carbon,nutrients and structure at different soil depths.[Method]The study was based on a long-term straw returning experiment established in 2009,with a double rice system as the research object.Four treatments were set up:no straw returning and no fertilizer control(CK),chemical fertilizer only(F),straw burning and returning(SBR),and full returning(SR).In 2021,samples were taken to analyze the physical properties of the soil,aggregate structure,the content of carbon,nitrogen and available nutrients in each soil layer,and the formation of double-cropping rice yield.[Result]Compared with CK,all fertilization treatments could improve soil physical and chemical properties and carbon and nitrogen contents.Compared with SBR and F treatments,SR significantly increased the soil moisture content and total porosity of double-cropping paddy fields,while reducing soil bulk density,with a decrease of 12.0％-17.3％in early rice and 10.7％-16.0％in late rice.SR treatment significantly increased the content of large aggregates(＞2 mm)and the average mass diameter and geometric diameter of soil in the 0-15 cm layer of double-cropping paddy fields,which was conducive to promoting the formation and stability of large aggregates,and the effect was the most significant in the 0-5 cm layer of soil.SR treatment also significantly increased the organic carbon content in each soil layer of 0-30 cm and promoted the increase of total nitrogen content in the 10-30 cm layer of soil,while there was no significant difference in organic carbon and total nitrogen between SBR and F treatments.At the same time,SR treatment significantly increased the content of available nutrients,such as ammonium nitrogen,alkali-hydrolyzable nitrogen and available phosphorus in the 0-10 cm layer of soil,but the nitrate nitrogen content only significantly increased in the 0-10 cm layer of soil in the early rice season.In addition,compared with F treatment,SR significantly increased the content of slow-release potassium in each soil layer in the late rice season,thereby significantly increasing the yield of late rice.[Conclusion]Overall,direct straw returning to the field was beneficial to increase the content of large soil aggregates in the 0-15 cm soil layer of double-cropping rice fields,promote the increase of available nutrients in the 0-10 cm soil and the content of organic carbon,total nitrogen and slow-release potassium in deep soil,and achieve stable and high yields.

Paddy fields serve as both significant carbon (C) sinks and sources. Straw biochar application has been identified as an effective material for C sequestration and the reduction of greenhouse gas (GHG) emissions. However, comprehensive assessments of crop production, carbon footprint (CF) and net ecosystem economic benefits (NEEB) of incorporating biochar produced from equivalent amounts of straw into double-cropping rice systems remain unclear. A three-year field experiment was conducted with four treatments including conventional fertilization (SF), double-cropping rice straw return (DSR), biochar return after early rice harvest followed by straw return after late rice harvest (BSR), and double-cropping biochar return (DBR). Compared to the SF treatment, DSR significantly increased cumulative CH4 and N2O emissions, thereby raising the global warming potential (GWP). In contrast, DBR consistently reduced GWP by suppressing methanogen abundance and enhancing methanotrophic activity. Although BSR initially increased CH4 emissions during early rice season, it overall mitigated late rice season emissions in the years. DSR, DBR and BSR significantly improved SOC storage compared to SF, with DBR showing the greatest soil C sequestration. Consequently, DBR achieved the largest reduction in net GWP and CF, and also generated the highest NEEB. Notably, BSR obtained the highest grain yield while maintained competitive GHG mitigation and C sequestration benefits. These findings suggest that straw-derived biochar amendment, particularly under the DBR measure, presents a superior strategy for climate change mitigation and economic return, while the BSR strategy offers a viable trade-off for prioritizing grain yield, thereby supporting sustainable rice production.

Reduced panicle nitrogen fertilizer (PNF) impacts indica rice grain quality by altering starch and protein composition, but the underlying mechanisms remain unclear. Field and pot experiments involving four PNF treatments (NE: full basal shift; LN: zero panicle nitrogen; DN: 50% reduction in panicle nitrogen; NN: normal panicle nitrogen) showed that, compared to the NN treatment, the NE, LN, and DN significantly increased amylose content while decreasing processing and appearance qualities, and protein content. Meanwhile, the LN and DN treatments decreased the proportion of amylopectin extremely short chains (DP 0-12) and short chains (DP 13-36), large granule starch, and starch gelatinization enthalpy, while increased the amylose extremely long chain, resulted in increasing peak viscosity and breakdown, and decreasing setback, ultimately improving rice eating quality. Furthermore, compared to the NN treatment, both the NE and LN treatments significantly downregulated genes governing nucleic acid processing (endonucleases, phosphodiester hydrolysis), RNA modification, and chloroplast function; and the anabolic substances related to protein, including sphingolipids, amino acids, and purines, thereby impairing grain filling and diminishing the processing, appearance, and nutritional qualities. In contrast, the LN and DN treatments upregulated genes involved in trehalose synthesis, driving the conversion of trehalose to glucose-1-phosphate and thereby facilitating ADP-glucose formation. These metabolic approaches decreased short-chain amylopectin synthesis while increasing long-chain amylose, contributing to the improvement of rice eating quality, especially for high-quality indica rice. Overall, the DN treatment achieves the optimal improvement effect on eating quality while ensuring good agronomic traits of the rice.

The practice of returning straw enhances the accumulation of soil organic carbon (SOC), dissolved organic carbon (DOC), and microbial communities. Nonetheless, the mechanisms in which microbes affect the variations in SOC and DOC during rice critical growth stages remain unclear. This research examines SOC, DOC, and microbial communities at panicle initiation (PI), heading (HS), and maturity (MS) stages in a paddy field, 13 years after long-term straw incorporation under no chemical fertilizers application with straw removal (CK), straw removal with only chemical fertilizer application (F), straw burning return with some chemical fertilizer application (SBR), and straw return in situ with some chemical fertilizer application (SR). Compared to CK, the other treatments significantly enhanced SOC levels throughout all growth stages. Notably, SR exhibited an average increase of 37.9% during the early rice season and 41.9% during the late rice season. Compared to F and SBR, SR significantly increased SOC by 7.1% at the PI stage of early rice, and by 9.2% and 10.1% at all late rice growth stages, respectively. SR also significantly enhanced the DOC level at the late growth stages of both rice seasons. Furthermore, SR enhanced microbial diversity at the PI stage in both rice seasons, aiding SOC accumulation. Although DOC had a positive relationship with microbial diversity in the early rice season, this relationship turned negative in the late rice season, likely due to the influence of the phylum Actinobacteria. Moreover, the significant enrichment of Cyanobacteria under SR at all stages of the late rice season was associated with an increase in SOC content. These results highlight the importance of Actinobacteria and Cyanobacteria in promoting the formation of SOC and DOC during key growth periods under long-term straw return. Future research requires the integration of 13C labelling with multi-omics to trace microbial-mediated straw carbon sequestration.

Nanomaterials (NMs) have been increasingly used to improve crop photosynthesis under diverse environments, However, the factors affecting the response of crop photosynthesis to NMs still remain insufficiently known. In the present study, a meta-analysis was conducted to investigative the NM effects on leaf photosynthesis-related parameters in maize, rice and wheat plants. Our results suggest that leaf photosynthetic rate (A) can be significantly improved by NMs through enhanced stomatal conductance, leaf transpiration rate, leaf electron transport rate, and chlorophyll b content, and the NM effects on A were similar among different crop species. We also found that positive effects of NMs on A were stronger under drought and salt stresses than under heavy metal, nanoplastic and normal (no abiotic stress) conditions, while the response of A to NMs under heat stress still needs further verification due to the limited studies, which remains critical knowledge gap requiring further research. Additionally, our present findings demonstrate that non-metallic NMs and seed application method are more beneficial for enhancing A than metallic NMs and other application methods, respectively. More importantly, our results indicate that the impacts of NMs on A observed under laboratory conditions should be carefully examined under field conditions prior to large-scale application. Besides, decreasing the application frequency of NMs with small size and low dosage has the potential to maximize crop A while also reducing economic and environmental costs. Our current findings should prove beneficial for future studies aimed at enhancing crop photosynthesis and yields under varying environments through the application of NMs.

Magnesium (Mg) plays crucial roles in regulating crop photosynthesis, yet its impacts on photosynthesis when light intensity is suddenly increased remain under-examined. A hydroponic experiment was conducted in two rice cultivars (ZJZ17 and NJ9108) under two Mg concentrations (40 and 0 mg Mg L−1), and the responses of leaf gas exchanges and chlorophyll fluorescence parameters to a single step increased light intensity were also examined. Leaf photosynthetic rate (A) at final steady state during induction was significantly decreased by 82

Early-season rice in the middle and lower reaches of the Yangtze River is vital for China's food security, but the planting area has sharply decreased in recent years due to its poor appearance and taste quality, as well as low returns. Therefore, we collected and analyzed 334 early-season rice varieties released in the region from 2000 to 2022. To verify whether low-amylose content (L-Am) varieties can reduce chalkiness without compromising yield, two field experiments were conducted: a two-year consecutive experiment (2021-2022) using six representative varieties (low amylose, L-Am: 14.5-16.8%; medium-high amylose, MH-Am: 23.8-25.9%), and a one-year validation experiment (2024) utilizing 32 widely cultivated varieties. The results indicated that the amylose content (AC) of the 334 varieties showed a normal distribution, with varieties containing 18-20% AC being the most prevalent (23.6%), which resulted in L-Am varieties collectively accounting for 46.4%; additionally, AC was significantly positively correlated with chalky kernel rate (CKR) and chalkiness degree (CKD), and negatively correlated with panicles per m2 and length-width ratio (LWR), but showed no correlation with yield. Similarly, L-Am and MH-Am varieties achieved comparable yields through compensatory adjustments in field experiments: L-Am varieties had 12.8-13.9% more panicles per m2 but 3.6-7.3% lower 1000-grain weight. Moreover, L-Am varieties exhibited superior grain quality, with 70.8-73.5% and 54.0-62.1% lower CKR and CKD, respectively. Physiological analyses revealed that L-Am varieties exhibited a smaller maximum grain-filling rate (GFRmax) and amylose accumulation rate (GAmRmax), mean grain-filling rate (GFRmean) and amylose accumulation rate (GAmRmean), longer active grain-filling/amylose accumulation periods (D), and higher activities of soluble starch synthase (SSS) during grain-filling stages. These results demonstrate that early-season rice varieties with low AC tend to exhibit significantly lower chalkiness. Physiologically, this superior appearance quality is strongly associated with maintained yield through compensatory yield components and distinct starch synthesis kinetics, offering a practical strategy for enhancing both quality and productivity in early-season rice.

Abstract Phosphorus (P) fixation in soils constrains its bioavailability, driving the evolution of adaptive strategies in plants, such as root morphology plasticity and exudation. This study systematically compared changes in root exudation pattern in a low-P-tolerant rice cultivar “Dalixiang” and a P-susceptible cultivar “Meixiangzhan” under different light intensities and P supplies. The results showed that, (1) Under P deficiency, Dalixiang exhibited a significantly increased root-to-shoot ratio, whereas Meixiangzhan showed a weaker ability to cope with P deficiency and low light. (2) Light intensity exerts a quantitatively greater influence on root exudation profiles than P supply, as evidenced by both the number of differential metabolites (301 vs. 185) and the magnitude of fold changes in key compounds. (3) The tolerant cultivar exhibited greater metabolic flexibility, releasing a broader spectrum of exudates across environments. Key pathways, including amino acid metabolism, were reconfigured by both stimuli. (4) Several previously unreported metabolites co-regulated by light intensity and P availability demonstrated their functional relevance. Notably, α-methylene-γ-butyrolactone significantly promoted root and shoot growth under P deficiency, while citraconic acid and xanthoxic acid enhanced P uptake. Our findings establish that light and P status dictates root physiological and metabolic traits, ultimately modulating rhizosphere P mobilization. This work provides a mechanistic framework for improving P-use efficiency in crops by leveraging the interplay between light management and root-mediated processes.

Straw return has demonstrated significant potential for enhancing carbon (C) sequestration and nitrogen (N) uptake while concurrently promoting plant productivity. However, the specific transport and distribution of C produced by photosynthesis and exogenous N within the rice plant-soil system under straw return remains unclear. A longterm straw return pot trial experiment was conducted in a double cropping rice system, incorporating treatments of inorganic fertilizer application with straw removal (F), straw burning and ash return with reducing inorganic fertilizers (SBR), and straw return with reducing inorganic fertilizers (SR) to investigate C sequestration and exogenous N uptake using 13C pulse and 15N isotope tracer techniques. The SR treatment had significantly higher soil 13C abundance, by 24.4 and 25.4%, respectively, 13C concentrations in aboveground plant parts, by 18.4 and 35.8% respectively, and 15N concentrations in rice panicles, by 12.8 and 34.3% than the SBR and F treatments. This enhancement contributed to a higher total organic C concentration and increased rice grain yield in the SR treatment. Furthermore, the SR treatment had significantly higher photosynthetic C, by 9.8%, which was directly transferred to soil C. The SR treatment had a higher distribution of photosynthetic C in the leaves and stems, but a lower distribution in the panicle compared to the SBR treatment. This finding is advantageous for sequestering photosynthetic C into the soil through straw return; conversely, opposite trends were observed in 15N distribution. In addition, rice plants in the SR treatment had increased N uptake from urea and soil N sources, enhancing N recovery by 9.2 and 12.5%, respectively, and reducing soil N residues. Correlation analysis showed that the SR treatment increased the concentrations of 13C in leaves and roots while decreasing the 15N abundance in all rice organs, thereby contributing to an increase in rice yield. The partial least square path model suggested that the increase in rice yield under the SR treatment was primarily linked to 13C accumulation within the rice plant-soil system. The results suggest that straw return increases the sequestration of photosynthetic C and exogenous N in the rice plant-soil system and increases N utilization efficiency, which subsequently improves both rice and soil productivity.

Early indica rice in Southern China frequently experiences high temperatures (HT) and strong light (SL) during grain filling, which accelerates grain maturity. In this study, two indica rice cultivars with different grain qualities under control (CK), HT, and HT + SL treatments to investigate their impacts on starch structure and physicochemical properties. The results demonstrated that HT and HT + SL treatments increased the amylopectin average chain length, long chain, relative crystallinity, large granule, and protein content (40.9 %-41.6 %), while decreasing amylose content (15.4 %-21.6 %) and branching degree compared to CK. This was due to a reduction in granule-bound starch synthase, soluble starch synthase, and starch branching enzymes, along with an increase in debranching enzyme activity, which altered the starch fine structure and diminished thermal stability and gelatinization viscosity. The HT + SL treatment exhibited a more pronounced impact, increasing the amylopectin middle chain (fb1) and relative crystallinity, while decreasing the branching degree and amylopectin short-chain length, indicating that SL exacerbated the deterioration of starch structure. Nevertheless, the starch physicochemical properties of high-quality cultivar were relatively less affected by the HT + SL conditions, suggesting a potential for improved utilization of starch in high-quality early indica rice in food processing.

The underlying mechanisms of warming effects on rice protein content have not been thoroughly investigated in the double rice cropping system. Here, a 2-year field experiment was conducted to clarify the physiological mechanisms related to nitrogen (N) uptake and assimilation under warming. The results showed that warming significantly increased albumin (16.7%), globulin (2.9%), and glutelin (26.1%) contents in early rice, while it increased prolamin (6.3%) and glutelin (13.4%) contents in late rice. The increased protein content under warming was associated with the elevated N concentration in the panicle, which was partly caused by the enhanced N uptake in early rice but not in late rice. A 15N pot experiment demonstrated that warming improved total N uptake from soil in both early and late rice; however, N uptake from fertilizer was increased and decreased by warming in early and late rice, respectively, resulting in improved total N uptake in early rice but not in late rice. Additionally, our results confirmed that increased soil net N mineralization rate and root activity contributed to the increased N uptake from soil under warming for both early and late rice. Furthermore, the activities of key enzymes, including glutamine synthetase, glutamate synthase, glutamic-oxaloacetic transaminase, and glutamate-pyruvate transferase, were increased, while protein hydrolysis was suppressed by warming in both early and late rice. Our findings indicate that the increase in protein components under warming conditions is due to improved N uptake in early rice and increased protein synthesis in both early and late rice.

Straw return has demonstrated significant potential for enhancing carbon (C) sequestration and nitrogen (N) uptake while concurrently promoting plant productivity. However, the specific transport and distribution of C produced by photosynthesis and exogenous N within the rice plantu2013soil system under straw return remains unclear. A long-term straw return pot trial experiment was conducted in a double cropping rice system, incorporating treatments of inorganic fertilizer application with straw removal (F), straw burning and ash return with reducing inorganic fertilizers (SBR), and straw return with reducing inorganic fertilizers (SR) to investigate C sequestration and exogenous N uptake using 13C pulse and 15N isotope tracer techniques. The SR treatment had significantly higher soil 13C abundance, by 24.4 and 25.4%, respectively, 13C concentrations in aboveground plant parts, by 18.4 and 35.8% respectively, and 15N concentrations in rice panicles, by 12.8 and 34.3% than the SBR and F treatments. This enhancement contributed to a higher total organic C concentration and increased rice grain yield in the SR treatment. Furthermore, the SR treatment had significantly higher photosynthetic C, by 9.8%, which was directly transferred to soil C. The SR treatment had a higher distribution of photosynthetic C in the leaves and stems, but a lower distribution in the panicle compared to the SBR treatment. This finding is advantageous for sequestering photosynthetic C into the soil through straw return; conversely, opposite trends were observed in 15N distribution. In addition, rice plants in the SR treatment had increased N uptake from urea and soil N sources, enhancing N recovery by 9.2 and 12.5%, respectively, and reducing soil N residues. Correlation analysis showed that the SR treatment increased the concentrations of 13C in leaves and roots while decreasing the 15N abundance in all rice organs, thereby contributing to an increase in rice yield. The partial least square path model suggested that the increase in rice yield under the SR treatment was primarily linked to 13C accumulation within the rice plantu2013soil system. The results suggest that straw return increases the sequestration of photosynthetic C and exogenous N in the rice plantu2013soil system and increases N utilization efficiency, which subsequently improves both rice and soil productivity.

Rice growth and yield performance are closely related to climate variables and soil water regimes. Therefore, in this study, normal humidity (NH) and high humidity (HH) treatments of rice canopy were performed and combined with continuous flooding (CF), alternate wetting and drying (AWD), and drought cultivation (DC). The changes in crop physiology were monitored in a 2-year artificial intelligence greenhouse experiment. Creating HH lowered the seed setting rate, grains per panicle and yield relative both under AWD and CF, but was rather beneficial under DC. The HH decreased the soil plant analysis development (SPAD) parameter and net photosynthetic rate while leaf surface temperature, antioxidant enzyme activity and malondialdehyde (MDA) level got increased. Additionally, HH increased the contents of abscisic acid (ABA), gibberellin (GA3) and jasmonic acid (JA) and the activities of key starch synthase, increasing the grain filling rate while shortening the active filling duration. The rice yield of AWD treatment under HH condition was the highest, mainly because the net photosynthetic rate, pollen viability and key starch synthase activity were maintained at a higher level. The AWD measures can be adopted to maintain high rice yields under high humidity conditions, while yields can be improved by increasing canopy humidity under persistent drought conditions.

Climate warming affects rice seed vigor during ripening, which plays a crucial role in seed quality. However, the actual response of rice seed vigor to warming is still unclear. In this study, seeds after warming treatment in a double rice cropping system were used to determine seed vigor and related physiological traits during germination. Warming treatment significantly improved the germination index (GI), seed vigor index (VI), and seedling dry weight (SDW) for the late-season rice seeds but had no effect on hull thickness, grain weight, and starch and protein contents for both early- and late-season rice seeds, and these parameters were highly associated with germination rate, GI, VI, and SDW. Warming treatment increased gibberellin content and α-amylase and β-amylase activities in endosperm and coleoptile in both seasons during the later stage of germination, reaching a significant level on the 7th d. Moreover, IAA content of the coleoptile was consistently increased but decreased in the endosperm in response to warming, and warming did not affect zeatin content. These results suggest that future global warming will improve rice seed vigor by regulating the synthesis of endogenous hormones and amylases, especially in the late-season rice.

Post-heading high temperatures occurred frequently in late indica rice regions in southern China recently, but the effects of high post-heading temperature on rice yield and quality under nitrogen application including nitrogen management (NM) and panicle fertilizer (NPF) were still unclear. Therefore, the grain yield and quality of late indica rice cultivars were compared in 2020 (ambient temperature) to 2019 (warming 2.3 degrees C) and 2021 (warming 3.5 degrees C). The results showed that moderate NPF can increase the yield, protein content (PC) and brown rice rate, and reduce the chalkiness and amylose content (AC) under naturally high temperatures. The proportion and application of NPF values higher than 22.5%, 36 kg center dot ha(-1) effectively improved grain yield, processing and appearance qualities, and PC, while reducing AC of late indica rice under natural warming. The temperature parameters, AC and PC during the total growth period could explain 81.7%, 90.7% and 89.6% of the variation in rice processing qualities, appearance qualities and gel consistency, respectively. The finding demonstrated that the optimum T-mean of improving rice yield and quality was 29.0 degrees C before heading and 21.1 degrees C after heading under NM, and 28.6 degrees C before heading, and 22.9 degrees C after heading under NPF. This study suggested that optimizing nitrogen management strategies under future climate warming conditions can synergistically increase indica rice yield and quality.

Double-season late indica rice frequently experiences low temperature accompanying with low light stress during the grain filling stage in southern China, which alters the carbon and nitrogen metabolism of the rice grains, thereby impacting both grain yield and quality. However, the physiological mechanism is still unclear. A pot experiment using two late indica rice cultivars (high-quality and common-quality rice cultivars) was conducted under control (CK), low temperature (LT) and low temperature and light (LT+LL) to investigate the grain filling, photosynthetic characteristics, carbon and nitrogen metabolic enzymes and related gene expression. The results indicated that both LT and LT+LL treatments primarily reduced grain weight in the two cultivars compared to CK. This effect was particularly pronounced for LT+LL, which showed a significant difference in both superior and inferior grains of the common-quality rice cultivar. This reduction in grain weight was attributed to an average decrease in the photosynthetic rate of rice leaves by 23.5%, a decrease in Fv/Fm by 6.2%, and a decrease in the original grain filling rate by 10.3%. LT and LT+LL treatments decreased the activities of soluble starch synthase (SSS), granules bound starch synthetase (GBSS) and starch branch enzyme (SBE) in the early grain filling stage, and its related gene expression including OsAGPL2, OsAGPS2b, OsGBSSI and OsSSIIIa, and the influence degree was intensified by LT+LL, compared with LT. For nitrogen metabolism, the activity of glutamic oxalic aminotransferase (GOT) also significantly decreased by LT and LT+LL during grain filling in the cultivars, which was relatively lower under LT+LL, and only decreased the glutamic pyruvic transaminase (GPT) in the early grain filling stage but increased in the later period. However, the related gene expressions of OsGOT1B and OsGS1;3 were enhanced significantly by LT and LT+LL treatments, and reached the highest level under LT+LL treatment, implying the disordered process of nitrogen metabolism. The results suggest that low temperature decreased photosynthetic traits to hinder grain filling in the cultivars, mainly derived from the worsened carbon and nitrogen metabolism, and LT+LL combined stress aggravated the damage degree.

This study conducted a two-year field artificial intelligence (AI) greenhouse rice planting experiment with different canopy humidity (normal humidity, NH; high humidity, and HH) and irrigation regimes (continuous flooding, CF; drought cultivation, DC; alternate wetting-drying, AWD) to test whether high canopy humidity from heading to maturity deteriorates rice grain quality, whether appropriate water management can alleviate these adverse effects, and the related mechanisms. The results showed that compared with NH, HH significantly decreased the head rice rate while increasing the protein, amino acid, amylopectin, amylose, and chalkiness. Moreover, HH significantly decreased the peak viscosity, breakdown, and number of small starch granules, while increasing the setback, number of large starch granules, relative crystallinity, gelatinization temperature, and enthalpy. Under NH and HH, AWD treatment resulted in a higher head rice rate, peak viscosity, breakdown, key enzyme activities of starch synthesis, amylose, amylopecan, relative crystallinity, small starch granules, gelatinization temperature, and enthalpy than DC and CF treatments, while lower chalkiness, setback, protein, amino acid, and large starch granules were observed. HH increased the chalkiness by promoting the formation of large starch granules, thus reducing the milling quality. The increase in amylose and relative crystallinity further causes HH to deteriorate the cooking and eating quality. AWD could alleviate the deterioration of rice grain milling, appearance, and eating quality caused by HH by improving starch granules.

In order to investigate the effects of weeds control on the yield formation and quality of doublecropping direct-seeded high-quality late indica rice, high-quality inbred rice Meixiangzhan 2（MXZ2） and highquality hybrid rice Taiyou 871（TY871） were used as materials, the field experiment with two treatments of chemical herbicide weeding（CW） and non-weeding（NW） were conducted. Compared with NW treatment, the grain yields of MXZ2 and TY871 under CW treatment increased by 75.71% and 76.00%, respectively, mainly due to the significant increase in the effective panicles and the spikelets per panicle. Compared with NW treatment, CW treatment could generally improve the processing quality and appearance quality of direct-seeded rice, and the gel consistency significantly reduced by 7.65% and 8.03%, respectively. CW treatment significantly increased the starch peak viscosity, hot viscosity, breakdown value and final viscosity of direct-seeded late rice,decreased the setback value, and improved the palatability of cooked rice. However, NW treatment significantly reduced the consistence of MXZ2, and did not differ on the chalkiness grain rate, amylose content and protein content. In all, spraying chemical herbicides for weed control significantly increased the yield of direct-seeded high-quality late rice, and it could significantly improve the processing quality of direct-seeded high-quality late rice, while reduced the chalkiness and gel consistency of rice. In addition, chemical weed control significantly affected the values of rice starch RVA profiles, which was beneficial to the improvement on cooking and eating quality.