Salt stress represents a significant abiotic stress factor that impedes the growth of rice. Nano-silicon has the potential to enhance rice growth and salt tolerance. In this experiment, the rice variety 9311 was employed as the test material to simulate salt stress via hydroponics, with the objective of investigating the mitigation effect of foliar application of nano-silicon on rice seedlings. The results demonstrated that NaCl stress markedly impeded the growth of rice seedlings after seven days of NaCl treatment. The foliar application of nano-silicon followed by NaCl stress alleviated the growth of rice seedlings, markedly improved the spatial conformation of the root system, and enhanced photosynthesis compared with that of NaCl stress alone. The activities of antioxidant enzymes were improved. The contents of antioxidants were increased, and the over-accumulation of ROS was reduced. Furthermore, the foliar application of nano-silicon was found to enhance the uptake of Si⁴⁺, K⁺, and Ca²⁺ in plants, while simultaneously reducing Na⁺ and Cl⁻ accumulation. Additionally, the content of IAA, CTK, GA, JA, and SA was increased, and ABA was decreased. In conclusion, the foliar application of nano-silicon has been demonstrated to alleviate salt stress injury and improve the growth of rice seedlings.

In order to explore the regulating role and the physiological and biochemical mechanisms of trans-abscisic acid (hereinafter referred as S-ABA) in the process of rice growth and development under salt stress, we took Chaoyou 1000 and Yuxiangyouzhan as materials and set up three salt concentration treatments, CK0 (Control treatment), N1 (50 mmol L⁻¹ NaCl), and N2 (100 mmol L⁻¹ NaCl), in potted trials; we aimed to study the mechanism of rice’s response to salt stress from the perspective of agricultural traits and physiological biochemicals and to improve rice’s resistance to salt stress through exogenously applying the regulating technology of S-ABA. The following results were obtained: Under salt stress, the growth of rice was significantly suppressed compared to CK0, exhibiting notable increases in agricultural indicators, photosynthesis efficiency, and the NA⁺ content of leaves. However, we noted a significant decrease in the K⁺ content in the leaves, alongside a prominent increase in NA⁺/K⁺ and a big increase in MDA (malondialdehyde), H₂O₂ (hydrogen peroxide), and O₂⁻ (superoxide anion). This caused the cytomembrane permeability to deteriorate. By applying S-ABA under salt stress (in comparison with salt treatment), we promoted improvements in agronomic traits, enhanced photosynthesis, reduced the accumulation of NA⁺ in leaves, increased the K⁺ content and the activity of antioxidant enzymes, and reduced the active oxygen content, resulting in a sharp decrease in the impact of salt stress on rice’s development. The application of S-ABA decreased the endogenous ABA (abscisic acid) content under salt stress treatment but increased the endogenous GA (gibberellin) and IAA (indole acetic acid) contents and maintained the hormonal homeostasis in rice plants. To summarize, salt stress causes damage to rice growth, and the exogenous application of S-ABA can activate the pouring system mechanism of rice, suppress the outbreak of active oxygen, and regulate NA⁺/K⁺ balance and hormone homeostasis in the blades, thus relieving the salt stress.

In Northeast China’s black soil rice cropping area, nitrogen (N) application is lower than in the south, yet excessive N fertilizer use persists, particularly in base fertilizers. This study aimed to assess the impact of reduced N and increased planting density on rice yields and photosynthetic matter production. From 2019 to 2020, a field split-plot experiment was conducted with two N rates (conventional N, CN: 120 kg ha⁻¹ and reduced basal N, RN: 108 kg ha⁻¹) and two planting densities (D1: 33.3 × 10⁴ hills ha⁻¹ and D2: 27.8 × 10⁴ hills ha⁻¹) using the rice varieties Kongyu131 (KY131) and Kendao24 (KD24). The results showed that RN increased the effective panicle formation rate but decreased the tiller numbers, dry matter accumulation, stems/sheaths transport capacity, leaf photosynthetic capacity, and yield by 2.67% compared to CN. D1 significantly boosted the dry matter accumulation, stems/sheaths transport, effective panicles, grains per square meter, and yield by 8.26% compared to D2. Interaction analysis revealed that RN under D2 conditions reduced the effective panicle percentage, harvest index, filled grain number, leaf area index (LAI), crop growth rate (CGR), and net assimilation rate (NAR) but increased the seed setting rate and 1000-grain weight. Under D1, RN reduced the LAI, CGR, and NAR at the tillering and heading stages but increased the NAR post-heading. Compared to CND2, RND1 increased the biomass, stems/sheaths transport, LAI, CGR, NAR, seed setting rate, 1000-grain weight, panicle numbers, and filled grains per square meter, compensating for the lower harvest index and effective panicle rate, achieving a 5.36% yield increase. KD24 outperformed KY131 in yield improvement. In summary, using 108 kg ha⁻¹ with a planting density of 33.3 × 10⁴ hills ha⁻¹ promotes tillering, enhances photosynthetic substance production stems/sheaths dry matter transport, and increases rice yields.

Seedling cultivation of rice (Oryza sativa L.) is a critical initial step in rice production. This study investigated the effects of sowing methods and strigolactone (GR24) on rice seedlings under salt stress. Results showed that drill-sown seedlings exhibited superior quality under normal conditions compared to broadcast-sown seedlings. Salt stress significantly increased the contents of Cl⁻, Na⁺, reactive oxygen species (ROS), and malondialdehyde (MDA), disrupted chloroplast structure and hormonal balance, and reduced gas exchange parameters and chlorophyll fluorescence parameters. Notably, drill-sowing conferred stronger salt tolerance than broadcast-sowing. Exogenous application of GR24 enhanced activities of antioxidant enzymes—including superoxide dismutase (SOD), ascorbate peroxidase (APX), peroxidase (POD), and catalase (CAT)—and elevated non-enzymatic antioxidant contents such as ascorbic acid (ASA), glutathione (GSH), total phenolics, and flavonoids, alongside related enzyme activities. Concurrently, GR24 reduced Na⁺ and Cl⁻ accumulation, lowered the Na⁺/K⁺ ratio, and increased the contents of K⁺, Ca²⁺, Mg²⁺, and hormones. Consequently, GR24 decreased MDA and ROS levels, protected membrane integrity, reduced electrolyte leakage, repaired chloroplast structure, and improved gas exchange and chlorophyll fluorescence parameters. Due to their superior spatial distribution and photosynthetic efficiency, drill-sown seedlings synergized with GR24 to enhance antioxidant capacity under salt stress, enabling more effective scavenging of peroxidative radicals, stabilization of the photosynthetic system, and mitigation of salt-induced growth inhibition. Ultimately, this combination demonstrated greater stress alleviation than broadcast-sown seedlings.

Rice (Oryza sativa L.) seedling raising is a vital step in rice cultivation. Salt stress severely impairs the growth of rice seedlings, whereas 5-aminolevu

Background Seedling raising of rice ( Oryza sativa L.) is a critical step in rice cultivation, and salt stress significantly impedes the growth of rice seedlings, while 5-aminolevulinic acid (5-ALA) plays a vital role in plant responses to various abiotic stresses. This experiment combines agronomic practices with chemical regulation to investigate the effects of drill sowing and 5-ALA on the photosynthetic system and ionic homeostasis of rice seedlings under salt stress. Results The results demonstrated that salt stress led to substantial accumulation of Na⁺ and Cl⁻ in rice seedling leaves, which disrupted the photosynthetic system and significantly inhibited seedling growth. Exogenous application of 5-ALA increased the content of chloroplast synthesis precursors, promoted the synthesis of photosynthetic pigments, reduced the accumulation of Na⁺ and Cl⁻, enhanced the levels of K⁺ and Ca²⁺, improved antioxidant enzyme activity, and mitigated oxidative damage. Consequently, it improved gas exchange parameters and chlorophyll fluorescence characteristics, and thus increased carbohydrate accumulation. Under drill sowing conditions, the application of 5-ALA resulted in higher levels of chloroplast synthesis precursors and carbohydrate accumulation compared to broadcast sowing. Under salt stress, this provided more energy substrates for chlorophyll synthesis and photosynthetic system repair, thereby enhancing peroxidation scavenging capacity, maintaining the stability of the photosynthetic system and ionic homeostasis, and resulting in stronger salt tolerance than broadcast sowing. Conclusion In conclusion, the combination of drill sowing and foliar application of 5-ALA synergistically maintained the photosynthetic system and ionic balance in rice seedlings under salt stress, improving their salt tolerance. This study provides a theoretical basis for optimizing sowing methods and chemical regulation in rice seedling cultivation in saline-alkali soils.