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This paper aims to solve the problem of high reseeding rates and mis-seeding rates in the rice multi-grain hole direct seeding process. A multi grain cluster air suction type rice hill direct seed metering device was developed, and its seeding mechanism was analyzed. Based on CFD-DEM coupling simulation and bench tests, this study explored and optimized the performance of the seed metering device, and carried out the seeding adaptability test. The simulation results were as follows: when the negative pressure was −5 kPa, the static pressure, dynamic pressure and velocity of the flow field reached the maximum. When the negative pressure was −4 kPa, the qualification index was 89.62%, the reseeding index was 4.36%, and the mis-seeding index was 6.02%. The results of the orthogonal rotation combination test of three factors and five levels showed that when the rotation speed, negative pressure and the length of stirring brush were 20.70 rpm, −4.0 kPa and 10.50 mm respectively, the seed metering performance was the best, the qualification index was 90.85%, the reseeding index was 4.41% and the mis-seeding index was 4.74%. The seed metering device had strong adaptability to the sowing of different rice varieties, and met the agronomic requirements of direct seeding and seeding in rice holes.

In the potato mechanical planting industry, the high multi-seeding rate and miss-seeding rate are problems that exist in many potato precision seed metering devices. The main potato seeds in China are cut potatoes with different shapes and sizes. However, there is a lack of research on precision seeding technology for cut potatoes, and the adaptability of many existing potato seeding devices on cut potato is poor. The mechanized precision seeding of potato can effectively reduce labor consumption, improve the seeding effect (decrease multi-seeding rate and miss-seeding rate), improve the improve production of potato per acre and improve the quality commodity potatoes. In response to the above issues, a precision seed metering device with novel scoops, which can adapt to various sizes and shapes of cut potatoes, was developed. In this study, the different seed collecting scenarios (SCSs) were constructed. Through the statics and kinematic analysis, the excess seeds removing (ESR) process was divided in to three areas. The kinematic model of seed potato was established to study the influence of different SCSs and sprocket rotational speeds on the ESR performance, and preliminary determined the appropriate sprocket rotational speed range for ESR process. Then, the coupled simulation results of EDEM and RecurDyn revealed that different sprocket speeds and SCSs had a significant influence on the ESR performance. Finally, the bench tests and field tests were conducted to verify the actual performance of the precision seed metering device. The results showed that, with the increase of the sprocket rotational speed, the ESR performance of the device improved, the multi-seeding rate significantly decreased, but the miss-seeding rate increased. High sprocket rotational speed will remove more seed potatoes and cause high miss-seeding rate. The bench tests showed the appropriate sprocket rotational speed for medium and large potato was 35 r/ min. The field tests obtained the best qualified-seeding rate of 91.54%, the miss-seeding rate of 3.08% and the multi-seeding rate of 5.38%. This study can provide theoretical reference for the design of potato precision seed metering device.

Synchronous pulses of seed masting and natural disturbance have positive feedbacks on the reproduction of masting species in disturbance‐prone ecosystems. We test the hypotheses that disturbances and proximate causes of masting are correlated, and that their large‐scale synchrony is driven by similar climate teleconnection patterns at both inter‐annual and decadal time scales. Hypotheses were tested on white spruce (Picea glauca), a masting species which surprisingly persists in fire‐prone boreal forests while lacking clear fire adaptations. We built masting, drought and fire indices at regional (Alaska, Yukon, Alberta, Quebec) and sub‐continental scales (western North America) spanning the second half of the 20th century. Superposed Epoch Analysis tested the temporal associations between masting events, drought and burnt area at the regional scale. At the sub‐continental scale, Superposed Epoch Analysis tested whether El Niño‐Southern Oscillation (ENSO) and its coupled effects with the Atlantic Multidecadal Oscillation (AMO) in the positive phase (AMO+/ENSO+) synchronize drought, burnt area and masting. We additionally tested the consistency of our synchronization hypotheses on a decadal temporal scale to verify whether long‐term oscillations in AMO+/ENSO+ are coherent to decadal variation in drought, burnt area and masting. Analyses demonstrated synchronicity between drought, fire and masting. In all regions the year before a mast event was drier and more fire‐prone than usual. During AMO+/ENSO+ events sub‐continental indices of drought and burnt area experienced significant departures from mean values. The same was observed for large‐scale masting in the subsequent year, confirming 1‐year lag between fire and masting. Sub‐continental indices of burnt area and masting showed in‐phase decadal fluctuations led by the AMO+/ENSO+. Results support the ‘Environmental prediction hypothesis’ for mast seeding. Synthesis. We provide evidence of large‐scale synchronicity between seed masting in Picea glauca and fire regimes in boreal forests of western North America at both inter‐annual and decadal time scales. We conclude that seed production in white spruce predicts changes in disturbance regimes by sharing the same large‐scale climate drivers with drought and fire. This gives new insides in a mechanism providing a fire‐sensitive species with higher than expected adaptability to changes in climate. Foreign Language French La synchronization du masting des semis et des perturbations naturelles ont un effet positif sur la reproduction d'espèces à fructification irrégulière dans des écosystèmes sensibles aux perturbations. Dans cette étude, on a testé les hypothèses qu'il existait une corrélation entre les perturbations et les causes ultimes du masting et que leurs synchronizations à grande échelle était dû à des patrons de téléconnections climatiques similaires, aux échelles décennales et interannuelles. L'espèce cible choisie pour tester cette hypothèse est l'épinette blanche (Picea glauca) une espèce à fructification irrégulière qui inopinément réussit à survivre dans les forêts boréales de l'Amérique du nord. On a créé des indices de masting, de sécheresse et de feux de forêt à des échelles régionales (Alaska, Yukon, Alberta, Québec) et subcontinental (Nord‐ouest de l'Amérique du nord) pour la deuxième moitié du XX siècle. L'association temporelle à l'échelle régionale entre masting, sécheresse et feux a été testée par le biais d'une analyse par époques superposées (Superposed Epoch Analysis). Au niveau subcontinental, la Superposed Epoch Analysis a été utilisée pour tester si la ENSO (El Niño‐Southern Oscillation) et ses effets cumulatifs avec l'AMO (Oscillation Atlantique Multi décennale) pendant des phases positives (AMO+/ENSO+) synchronisent le masting, la sécheresse et les feux. La constance de ses synchronizations a été testée sur une échelle temporelle décennale pour vérifier si les oscillations AMO+/ENSO+ sur le long terme étaient cohérente avec les variations des sécheresses, des surfaces brulées et du masting. Les analyses ont révélé la synchronization entre sécheresse, feux et masting. Dans toutes les régions, l'année qui précède un phénomène de masting a été sèche et plus propice aux incendies que d'habitude. Pendent les épisodes AMO+/ENSO+, les indices de sécheresse et de surface brulée à l'échelle subcontinentale ont montré des valeurs hors de la moyenne. De même, les phénomènes de masting à large échelle qui ont eu lieu dans l'année suivante, confirment le décalage d'un an entre les feux et la production de semis. Les résultats supportent l'hypothèse d'une prédiction environnementale (Environmental prediction hypothesis) pour le masting comme démontré avec la fluctuation parallèle sur une échelle décennale de la surface brûlée et du masting au niveau subcontinentale. En synthèse, on a prouvé la synchronisation à grande échelle entre les événements de masting de Picea glauca et le régime des feux de couronne dans les forêts boréales du nord‐ouest de l'Amérique du nord, que ce soit à des rythmes interannuelles ou décennales. La production abondante de semis chez l'épinette blanche, étant stimulée par les mêmes facteurs qui règlent la sécheresse et les incendies, suit donc les changements du régime des perturbations. Cela nous donnent de nouvelles connaissances sur un mécanisme qui permet à une espèce sensible au feu d'avoir un potentiel d'adaptation au changement climatique plus haut que prévu. We provide evidence of large‐scale synchronicity between seed masting in Picea glauca and fire regimes in boreal forests of western North America at both inter‐annual and decadal time scales. We conclude that seed production in white spruce predicts changes in disturbance regimes by sharing the same large‐scale climate drivers with drought and fire. This gives new insides in a mechanism providing a fire‐sensitive species with higher than expected adaptability to changes in climate.

Summary Flooding is a widespread natural disaster that causes tremendous yield losses of global food production. Rice is the only cereal capable of growing in aquatic environments. Direct seeding by which seedlings grow underwater is an important cultivation method for reducing rice production cost. Hypoxic germination tolerance and root growth in waterlogged soil are key traits for rice adaptability to flooded environments. Alternative oxidase (AOX) is a non‐ATP‐producing terminal oxidase in the plant mitochondrial electron transport chain, but its role in hypoxia tolerance had been unclear. We have discovered that AOX1a is necessary and sufficient to promote germination/coleoptile elongation and root development in rice under flooding/hypoxia. Hypoxia enhances endogenous H2O2 accumulation, and H2O2 in turn activates an ensemble of regulatory genes including AOX1a to facilitate the conversion of deleterious reactive oxygen species to H2O2 in rice under hypoxia. We show that AOX1a and H2O2 act interdependently to coordinate three key downstream events, that is, glycolysis/fermentation for minimal ATP production, root aerenchyma development and lateral root emergence under hypoxia. Moreover, we reveal that ectopic AOX1a expression promotes vigorous root and plant growth, and increases grain yield under regular irrigation conditions. Our discoveries provide new insights into a unique sensor–second messenger pair in which AOX1a acts as the sensor perceiving low oxygen tension, while H2O2 accumulation serves as the second messenger triggering downstream root development in rice against hypoxia stress. This work also reveals AOX1a genetic manipulation and H2O2 pretreatment as potential targets for improving flooding tolerance in rice and other crops.

The study presents the design of a precision maize hill-drop dibbler based on fluid control and zero-speed seeding theory, developed to overcome challenges of poor planting precision, seed damage, limited terrain adaptability, and low water-use efficiency in maize cultivation across the hilly regions of Southwest China. To this end, a novel precision fluid hill-drop planter was designed, integrating fluid control with zero-speed seeding theory. The device employs a seed-liquid separation and terminal mixing design, where a crank-connecting rod-driven piston pump ensures precise fluid delivery. A direct comparative experimental framework was established, evaluating the proposed planter against a traditional spoon-wheel seeder under identical bench-test conditions. Performance was assessed through CFD-DEM coupled simulation and systematic experiments across multiple dimensions: seeding precision (qualified, multiple, and miss index), hill-forming characteristics, and fluid performance (water application per hill, seed bounce distance). The comparative results demonstrated that within an operating speed range of 1.2 ~ 1.6 m/s, the new planter achieved a qualified index exceeding 91%, a significant improvement of 12.5% over the conventional device. The seed bounce distance was controlled within 5.4 mm, representing a 63.2% reduction. Furthermore, the system exhibited excellent operational stability, with a coefficient of variation for water application per hill of less than 2% and a check valve leakage rate below 3%. Through collaborative parameter optimization, breakthrough indicators were achieved: a 94.8% seed-water coincidence rate and a hill spacing deviation of no more than 1.0%. This research validates the proposed planter's superior performance and reliability, providing an effective technical solution to enhance sowing uniformity and water-use efficiency in complex terrain.

As a photophilous plant, rice is susceptible to low-light stress during its growth. The Sichuan Basin is a typical low-light rice-producing area. In this study, eight rice varieties with different shade tolerances were studied from 2021 to 2022. The physiological adaptability and yield formation characteristics of rice were studied with respect to photosynthetic physiological characteristics and dry matter accumulation characteristics, and the response mechanism of rice to low light stress was revealed. The results showed that the shading treatment significantly increased the chlorophyll a, chlorophyll b, and total chlorophyll contents in the leaves of direct-seeded rice after heading, and the total chlorophyll content increased by 1.68–29.70%. Nitrate reductase (NR) activity first increased and then decreased under each treatment, and the shading treatment reduced the NR activity of direct-seeded rice. Compared to the control treatment, the peroxidase (POD) activity of each variety increased from 7 to 24 d after the shading treatment. The transketolase (TK) activity in direct-seeded hybrid rice increased under low light stress. Compared with the control, shading treatment significantly reduced the aboveground dry matter, grain number per panicle, and seed setting rate of direct-seeded rice at the full heading stage and maturity stage, thus reducing the yield of direct-seeded rice by 26.10–34.11%. However, under the shading treatment, Zhenliangyou 2018 and Jingliangyou 534 maintained higher chlorophyll content and related enzyme activities, accumulated more photosynthetic products, and reduced yield. In general, Zhenliangyou 2018 and Jingliangyou 534 still had a yield of 7.06–8.33 t·hm−2 under low light. It indicated that Zhenliangyou 2018 and Jingliangyou 534 had better stability and stronger tolerance to weak light stress and had a higher yield potential in weak light areas such as Sichuan.

Direct seeding of rice is a lightweight and simple cultivation method, which can effectively promote rice production. Anaerobic germination tolerance is one of the main traits of rice adaptability to direct seeding. The mining of related genetic loci, analysis of anaerobic traits and screening of tolerance genes provided valuable genetic resources for improving the anaerobic germination ability of direct seeding rice. This study conducted a dynamic genome-wide association study (GWAS) based on coleoptile-related traits of 591 rice natural populations, and a total of 317 SNP sites were detected. Integrated dynamic widely targeted metabolomics analysis, we found that xanthine, l-alanine and GABA may be key biomarkers that are sensitive and respond strongly to hypoxic stress perception. By WGCNA analysis of targeted metabolomics and transcriptomics, a total of 3 modules were obtained that were significantly correlated with the above three marker metabolites, namely dark green, dark gray and light green modules, respectively, and several key structural genes of OsAlaAT1, OsGAD4, OsAAH and Os09g0424600 that may affect hypoxic germination were screened from the 3 modules. Among them, OsAlaAT1 (Os10g0390500), located in Chr10-12877840, which is within the GWAS location range of CVAN3d, is considered to be a more reliable candidate gene. Overall, in addition to providing new insight into the metabolic regulation of l-alanine, GABA and xanthine during hypoxic germination of rice. This study also provided a reference for the basic theoretical research and breeding application research on the related traits of anaerobic germination in direct-seeding rice.

To meet the diverse seeding requirements of super hybrid rice, common hybrid rice, and conventional rice—which vary from 1 to 3 seeds, 2 to 4 seeds, and 5 to 8 seeds per hole, respectively—this study developed a branched air-chamber type pneumatic seed metering device for rice. The device utilizes an air chamber control board to manage the branched air chamber casing, enabling precise adjustments to the seeding quantity. This study presents a theoretical analysis of the seed metering device’s operation and its critical components. Structural parameter optimization was conducted using Ansys-Fluent (2021 R1) software, followed by multi-objective optimization of operational parameters through bench testing. Simulation results indicated that optimal vacuum pressure in the seed metering disc pores reached a maximum of 857 Pa with a chamber depth of 22 mm, an angle of 100°, and a cavity depth of 25 mm, achieving a minimal coefficient of variation of 0.86%. Bench test results showed that for seeding targets of 1 to 3 rice seeds per hole, the optimal operational parameters were: two openings, a working vacuum of 1355 Pa, and a rotor speed of 32.78 r/min, resulting in a missed seeding rate of 4.70%, a qualification rate of 85.81%, and a re-seeding rate of 9.49%. For targets of 2 to 4 seeds per hole, the best parameters included three openings, a working vacuum of 1357 Pa, and a speed of 32.87 r/min, with a missed seeding rate of 4.60%, a qualification rate of 85.59%, and a re-seeding rate of 9.81%. For 5 to 8 seeds per hole, optimal parameters were six openings, a vacuum of 1339 Pa, and a rotor speed of 31.07 r/min, yielding a missed seeding rate of 4.09%, a qualification rate of 87.27%, and a re-seeding rate of 8.64%. These findings demonstrate that the branched air-chamber type pneumatic seed metering device effectively meets the varied direct seeding requirements of rice, enhancing the adaptability of pneumatic seed metering devices to different seeding quantities in rice and potentially informing the design of pneumatic seeders for other crops.

Volunteer wheat commonly occurs and spreads rapidly in the main wheat-producing areas of China, seriously impacting cultivated wheat production. Limited information is currently available regarding the adaptability and germination traits of volunteer wheat. Therefore, this study’s aim was to evaluate the effects of environmental conditions on the germination and emergence of volunteer wheat seeds through laboratory experiments. The results showed that the germination percentages and viability of volunteer wheat were significantly higher than those of cultivated wheat at a low temperature of 5 °C, and they were lower than those of cultivated wheat at high temperatures of above 30 °C. Compared to cultivated wheat, volunteer wheat was able to tolerate higher salinity and lower osmotic potential, especially long-dormancy volunteer wheat. The secondary germination ability of volunteer wheat was higher than that of cultivated wheat after water immersion. Furthermore, volunteer wheat could not emerge normally when the seeding depth was greater than 8 cm, and the emergence ability of the volunteer wheat was weaker than that of the cultivated wheats when the seeding depth was 4–8 cm, which indicates that the deep tillage of cultivated land could effectively prevent the spread of volunteer wheat. This study revealed differences in the germination characteristics of volunteer wheat and cultivated wheat under the influence of different environmental factors, which provides a basis for future studies concerning the control of volunteer wheat.

One of the least understood aspects of prion diseases is the structure of infectious prion protein aggregates. Here we report a high-resolution cryo-EM structure of amyloid fibrils formed by human prion protein with the Y145Stop mutation that is associated with a familial prion disease. This structural insight allows us not only to explain previous biochemical findings, but also provides direct support for the conformational adaptability model of prion transmissibility barriers. A cryo-EM structure of disease-related human Y145Stop prion protein amyloid fibrils explains species-dependent seeding barriers in prion protein amyloid propagation.