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Mechanical transplanting has become an important part of modern Chinese rice production, and an inadequate sowing rate severely inhibits rice seedling growth and development. Precision drill sowing is an effective method for obtaining higher quality seedlings during machine transplanting. There is a lack of systematic research on the precision drilling of rice. Therefore, we carried out research on the quality of machine-transplanted seedlings and precision drill sowing transplantation. A greenhouse experiment (Liaoning Rice Research Institute) and field experiment (Sujiatun District, Shenyang City, Liaoning Province, China) were conducted between 2020 and 2021 to analyze the influence of precision drill sowing on rice growth and yield. Precision drill sowing was conducted at four sowing rates (3400, 3600, 3800, and 4000 seeds/tray), and traditional broadcasting was also conducted at a sowing rate of 4000 seeds/tray. We evaluated the seedling rice quality, physiological and biochemical characteristics and transplanting quantity. The results indicated that precision drill sowing at a sowing rate of 3400 seeds/tray resulted in the highest plumpness value (0.18) and seedling strength index (0.42) of individual plants. However, the empty hill rate was as high as 3.05%, which did not satisfy the field seedling number requirement. Precision drill sowing at a sowing rate of 4000 seeds/tray resulted in the lowest physiological (the average levels of SOD, POD and soluble protein were 311.78 µg/g, 8.25 µg/g and 1.28 µg/g) and biochemical indices of individual plants. The damaged seedling rate increased by 2.07%, and the dead seedling rate increased by 0.25%, resulting in poor seedling and transplanting quality. In this study, 3800 seeds/tray was the best option and had the highest yields of 10,776.60 kg/ha and 10,730.85 kg/ha over the two years. This sowing approach performs well in terms of field transplanting, provides a balance point between seedling number and quality and is conducive to rice yield production. The results of this study are important for improving rice seedling quality, enhancing field transplanting quantity and increasing rice yield and food security.

Nitrogen is a crucial element that impacts rice yields, and effective tillering is a significant agronomic characteristic that can influence rice yields. The way that reduced nitrogen affects effective tillering is a complex quantitative trait that is controlled by multiple genes, and its genetic basis requires further exploration. In this study, 469 germplasm varieties were used for a genome-wide association analysis aiming to detect quantitative trait loci (QTL) associated with effective tillering at low (60 kg/hm2) and high (180 kg/hm2) nitrogen levels. QTLs detected over multiple years or under different treatments were scrutinized in this study, and candidate genes were identified through haplotype analysis and spatio-temporal expression patterns. A total of seven genes (NAL1, OsCKX9, Os01g0690800, Os02g0550300, Os02g0550700, Os04g0615700, and Os04g06163000) were pinpointed in these QTL regions, and were considered the most likely candidate genes. These results provide favorable information for the use of auxiliary marker selection in controlling effective tillering in rice for improved yields.

Reducing nitrogen fertilizer application, selecting a reasonable planting density, and adding silicon fertilizer can be used together to decrease excessive nitrogen fertilizer inputs in rice fields, reduce production costs, and ensure stable rice yield. However, the dynamics of the stem and internodes, as well as the changes in the physical and physiological characteristics of rice under a combination of these three strategies, are still unclear. In this study, we aimed to clarify these effects to improve the efficiency of rice production in northeastern China. A 2-year field experiment was conducted using five treatments: a conventional densification treatment (DM), a densification combined with reduced N input (−20%) treatment (DLM), and three densifications combined with reduced N input (−20%) and basal silicon fertilizer treatments (low fertilizer: DLMS1; medium fertilizer: DLMS2; and high fertilizer: DLMS3). This study revealed that the addition of silicon fertilizer improved rice yield compared to that under reduced nitrogen or increased density treatments alone, prevented excessive ineffective tillering after a density increase, and increased the number of productive panicles. Among the treatments, the DLMS3 treatment had the highest yields of 10.53 t/ha and 10.73 t/ha over the 2 years. Reducing nitrogen and increasing density reduced the weight and length of single panicles, while the addition of silicon fertilizer was beneficial for improving stem toughness, improving the physical and physiological characteristics of the plants and panicles, and enhancing plant bending resistance. Among the treatments, DLMS3 had the highest bending resistance, which increased by 440.1 g and 503.8 g compared to the lowest values in the DM treatment in 2020 and 2021, respectively. Nitrogen reduction resulted in the lowest lodging index values, with DLMS3 having the lowest values in both years, which decreased by 19.6% and 22.5% compared to the highest values in DM (2020) and DLM (2021), respectively. This study indicates that the application of 150.0 kg/ha silicon fertilizer in combination with reduced nitrogen and increased density (DLMS3) reduces the lodging index while ensuring rice yield, preventing a tradeoff between yield reduction and lodging due to a density increase or due to nitrogen reduction combined with a density increase and allowing for a reduction in nitrogen fertilizer input, which could ensure a uniform yield and an increase in lodging resistance. These results provide a scientific basis for rice cultivation measures that lead to high yield and lodging resistance while protecting the environment.

The elevation of the snowline of the No. 1 Glacier in the Tianshan Mountains is increasing due to global warming, which has created favorable conditions for moss invasion and offers an opportunity to investigate the synergistic effects of incipient succession by mosses, plants, and soils. In this study, the concept of altitude distance was used instead of succession time. To investigate the changes of bacterial-community diversity in moss-covered soils during glacial degeneration, the relationship between bacterial community structure and environmental factors was analyzed and valuable microorganisms in moss-covered soils were explored. To do so, the determination of soil physicochemical properties, high-throughput sequencing, the screening of ACC-deaminase-producing bacteria, and the determination of ACC-deaminase activity of strains were performed on five moss-covered soils at different elevations. The results showed that the soil total potassium content, soil available phosphorus content, soil available potassium content, and soil organic-matter content of the AY3550 sample belt were significantly different compared with those of other sample belts (p < 0.05). Secondly, there was a significant difference (p < 0.05) in the ACE index or Chao1 index between the moss-covered-soil AY3550 sample-belt and the AY3750 sample-belt bacterial communities as the succession progressed. The results of PCA analysis, RDA analysis, and cluster analysis at the genus level showed that the community structure of the AY3550 sample belt and the other four sample belts differed greatly and could be divided into two successional stages. The enzyme activities of the 33 ACC-deaminase-producing bacteria isolated and purified from moss-covered soil at different altitudes ranged from 0.067 to 4.7375 U/mg, with strains DY1–3, DY1–4, and EY2–5 having the highest enzyme activities. All three strains were identified as Pseudomonas by morphology, physiology, biochemistry, and molecular biology. This study provides a basis for the changes in moss-covered soil microhabitats during glacial degradation under the synergistic effects of moss, soil, and microbial communities, as well as a theoretical basis for the excavation of valuable microorganisms under glacial moss-covered soils.

Osteoporotic vertebral compression fractures are a global issue affecting the elderly population. To explore a new calcium silicate bone cement, polylactic acid (PLGA)–polyethylene glycol (PEG)–PLGA hydrogel was compounded with tricalcium silicate (C3S)/dicalcium silicate (C2S)/plaster of Paris (POP) to observe the hydration products and test physical and chemical properties. The cell compatibility and osteogenic capability were tested in vitro. The rabbit femoral condylar bone defect model was used to test its safety and effectiveness in vivo. The addition of hydrogel did not result in the formation of a new hydration product and significantly improved the injectability, anti-washout properties, and in vitro degradability of the bone cement. The cholecystokinin octapeptide-8 method showed significant proliferation of osteoblasts in bone cement. The Alizarin red staining and alkaline phosphatase activity test showed that the bone cement had a superior osteogenic property in vitro. The computed tomography scan and gross anatomy at 12 weeks after surgery in the rabbit revealed that PLGA-PEG-PLGA/C3S/C2S/POP was mostly degraded, with the formation of new bone trabeculae and calli at the external orifice of the defect. Thus, PLGA-PEG-PLGA/C3S/C2S/POP composite bone cement has a positive effect on bone repair and provides a new strategy for the clinical application of bone tissue engineering materials.

Light, simple, and high-efficiency fertilization is currently an effective method used to improve quality and increase yield. Most research has only focused on the yield or quality of rice, and no effective or in-depth studies exist on the key stage of panicle, which is essential for these two aspects. This study aimed to determine the effect of applying Nitrogen (N) and Potassium (K) fertilizers on the yield and quality at different leaf ages. The rice cultivar, Shennong 265, was grown in the field-tube condition at the 5-leaf age with K fertilizer at different panicle stages. Five K fertilizer and four N fertilizer levels were applied simultaneously during two growing seasons in 2020–2021. The application of K fertilizer at different panicle stages significantly affected the yield and quality. The application of K and N fertilizers at the 12th-leaf-age increased the number of panicles and grains per panicle, thereby increasing the yield with an average increase of 23.20% over local farmer’s fertilization model (CK) in two years. Application at the 10th-leaf age reduced the starch and protein content of the rice and improved the nutritional quality and taste, with an average increase of 11.08 points compared to CK in two years. The processing quality was the best at the panicle K fertilizer application rate of 47.81–64.69 kg ha−1, and the starch and protein contents were the lowest at the panicle K fertilizer application rate of 56.25 kg ha−1. Under different panicle K fertilizer application rates, N fertilizers had great differences in processing quality but had slight differences in nutritional quality; that is, the starch and protein content (total protein and four protein components) significantly increased. The application of panicle N fertilizer mainly affected starch pasting viscosity (RVA profile characteristics). When panicle K fertilizer was applied after panicle N fertilizer, the yield and quality showed a trend of synergistic improvement. Although this improvement was a low-level synergy, it can still be a direction used to explore the synergistic improvement of output and quality.

Edema toxin (ET), which is composed of a potent adenylate cyclase (AC), edema factor (EF), and protective antigen (PA), is one of the major toxicity factors of Bacillus anthracis. In this study, we introduced mutations in full-length EF to generate alanine EF(H351A) and arginine EF(H351R) variants. In vitro activity analysis displayed that the adenylyl cyclase activity of both the mutants was significantly diminished compared with the wild-type EF. When the native and mutant toxins were administered subcutaneously in a mouse footpad edema model, severe acute swelling was evoked by wild-type ET, while the symptoms induced by mutant toxins were very minor. Systemic administration of these EF variants caused non-lethal hepatotoxicity. In addition, EF(H351R) exhibited slightly higher activity in causing more severe edema than EF(H351A). Our findings demonstrate that the toxicity of ET is not abolished by substitution of EF residue His351 by alanine or arginine. These results also indicate the potential of the mouse footpad edema model as a sensitive method for evaluating both ET toxicity and the efficacy of candidate therapeutic agents.