In order to analyze the physiological regulation mechanisms associated with exogenous melatonin on rice blast, this study treated rice seedlings with different concentrations of melatonin (0, 20, 100, and 500 µmol/L) in order to investigate the growth characteristics, root morphology, superoxide dismutase (SOD) activity, peroxidase (POD) activity, catalase (CAT) activity, malondialdehyde (MDA) content, hydrogen peroxide (H₂O₂) content, and soluble protein content of rice seedlings. The results indicated that 100 µmol/L of melatonin exhibited a significant effect, improving the growth and antioxidant capacity of rice seedlings under rice blast fungus infection. The disease resistance level of rice seedlings against rice blast significantly decreased by 31.58% when compared to the 0 µmol/L melatonin treatment, while the plant height, stem base width, plant leaf area, total root length, aboveground dry weight, aboveground fresh weight, and underground fresh weight significantly increased by 8.72% to 91.38%. Treatment with 100 µmol/L of melatonin significantly increased catalase activities and soluble protein content, with respective increases of 94.99% and 31.14%. Simultaneously, the contents of malondialdehyde and hydrogen peroxide significantly decreased, reaching 18.65% and 38.87%, respectively. The gray relational grade analysis indicated that hydrogen peroxide content and resistance level exhibit the highest gray relational grades with melatonin concentration and, so, can be used to evaluate the effect of melatonin on the severity of rice blast fungus infection. Furthermore, the membership function analysis revealed that the 100 µmol/L melatonin treatment had the highest membership function value, indicating a significant improvement in the resistance of rice seedlings to rice blast disease. In conclusion, 100 µmol/L of melatonin enhances the resistance of rice seedlings to rice blast disease through promoting their growth and strengthening their antioxidant defenses. This study provides new insights into the tolerance mechanisms of rice seedlings against rice blast disease.

With global climate warming, enhancing the heat stress tolerance of rice seeds is critical for ensuring crop yields and maintaining global food security. 2,4-Epibrassionolide (EBR) has been shown to effectively alleviate the adverse effects of heat stress on rice seed germination, but its mitigation mechanism has not been fully clarified. In this experiment, exogenous EBR was used as a seed priming agent. The activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), malondialdehyde (MDA), soluble protein contents, and plant hormone levels were measured during rice seed germination under heat stress (38 °C). We constructed a cDNA library for transcriptome sequencing analysis. The results showed that exogenous EBR could effectively alleviate the effect of heat stress on rice seeds by enhancing SOD, POD, and CAT enzyme activity; reducing the MDA content; and increasing the soluble protein content. Additionally, exogenous EBR increases the levels of GA and IAA while decreasing the ABA content. According to a transcriptomic analysis, exogenous EBR can induce the expression of key genes involved in GA, IAA, and ABA hormone biosynthesis and metabolism, regulating GA-, IAA-, ABA-, and H₂O₂-mediated signaling pathways to promote the germination of rice seeds under heat stress. This study provides new insights into the application of rice seed priming techniques.

The present study investigated the effect of the replacement of chemical fertilizers by organic fertilizers on agronomic traits of tobacco at maturity as well as on the conventional chemical quality of post-roasted tobacco leaves. To better understand the relationship between tobacco metabolites and roasted tobacco under organic nitrogen replacement treatments, post-roasting tobacco leaves were analyzed by an untargeted metabolomics analytical approach to identify key metabolites applicable to predicting tobacco quality. Methods: Yunyun Tobacco 87 was adopted as the test material in a field plot experiment with five fertilization treatments: T1 (100% chemical nitrogen fertilizer), T2 (25% organic nitrogen fertilizer + 75% chemical nitrogen fertilizer), T3 (50% organic nitrogen fertilizer + 50% chemical nitrogen fertilizer), T4 (75% organic nitrogen fertilizer + 25% chemical nitrogen fertilizer), and T5 (100% organic nitrogen fertilizer). Additionally, the non-targeted metabolomics approach was employed for the in-depth analysis of metabolites in roasted tobacco leaves. Results: The targeted metabolomic analysis identified 991 metabolites in the positive ion pattern and 673 in the negative ion pattern across all treatments. Among these, certain pathways such as alanine, aspartate, and glutamate metabolism, D-amino acid metabolism, purine metabolism, tryptophan metabolism, and galactose metabolism were up-regulated, whereas other pathways such as starch and sucrose metabolism, betalain biosynthesis, and biosynthesis of unsaturated fatty acids were down-regulated and significantly enriched with differential metabolites. This study revealed the significant differences in the metabolite composition under different fertilization conditions, with a strong correlation between metabolites and tobacco quality indices. Organic fertilizers were observed to enhance tobacco quality by influencing tobacco metabolism, providing a scientific basis for optimizing fertilization strategies and improving tobacco quality.

To sustain agricultural productivity and safeguard global food security, and confront the escalating challenges posed by climate change and water scarcity, it is essential to enhance the growth and productivity of rice under water stress. This study investigated the effects of lanthanum chloride on the chlorophyll fluorescence characteristics and grain yield of rice under different irrigation modes. The rice cultivar H You 518 was selected and sprayed 20, 100, or 200 mg·L⁻¹ lanthanum chloride at the booting and heading stages under deficit irrigation (where no rewatering was applied after the initiation of stress, allowing the water layer to evaporate naturally under high temperatures) or conventional irrigation (with daily rewatering to maintain a consistent water level). The results showed that the application of low concentrations lanthanum chloride promoted the chlorophyll content, whereas high concentrations decreased the chlorophyll content, under deficit irrigation, the effect of lanthanum chloride on the green fluorescence parameters of rice leaves at the booting stage was greater than that at the heading stage, and the booting stage was more sensitive to water deficit. The application of 100 mg·L⁻¹ lanthanum chloride reduced the initial fluorescence (F0) and the non-photochemical quenching coefficient (qN); promoted the activity of leaf photosynthetic system II (PSII); and maximized the photochemical quantum yield (Fv/Fm), photochemical quenching coefficient (qP), and PSII relative electron transfer efficiency (ETR). Under deficit irrigation, this treatment significantly enhanced grain yield by increasing the thousand-grain weight, spikelet filling rate, and number of grains per panicle. These results suggest that spraying 100 mg·L⁻¹ lanthanum chloride at the booting stage under deficit irrigation can effectively increase the chlorophyll content, thereby increasing the light energy conversion efficiency of the PS II reaction center, ultimately resulting in increased spikelet filling rate and grain yields.

Phosphorus, as a crucial element affecting the physical properties and chemical quality of tobacco leaves, is often used excessively in tobacco production, leading to a prolonged surplus in the soil that poses risks to both the environment and tobacco quality. Despite its importance, there is limited research on the variations in phosphorus levels among tobacco leaves positioned differently in high-phosphorus soils. Therefore, investigating the rational reduction of phosphorus fertilizers in phosphorus-rich soils is essential. This study was conducted in the Guiyang Tobacco Growing Area of Chenzhou, Hunan Province, China. The widely planted Yunyan 87 tobacco variety was utilized and three phosphorus levels were created, including CK representing farmers’ habitual phosphorus fertilizer treatment (P ₂ O ₅ 139.65 kg ha ⁻¹ ), P1 reducing phosphorus by 25 % with base fertilizer (P ₂ O ₅ 104.85 kg ha ⁻¹ ), and P2 reducing phosphorus by 50 % with base fertilizer (P ₂ O ₅ 69.9 kg ha ⁻¹ ). The effects of phosphorus dosage on the physical properties and chemical quality of tobacco were investigated. In the phosphorus-rich soils, the conventional phosphorus application (CK) was optimal for the 5th, 6th, 7th, and 10th leaves; reducing phosphorus by 25 % with basal fertilizer (P1) was optimal for leaves 7–12; and reducing phosphorus by 50 % with base fertilizer (P2) was optimal for leaves 9–11. The excessive phosphorus application could decrease the coordination between the physical properties and chemical composition of tobacco leaves, particularly affecting the leaf thickness, single-leaf weight, total sugar, and reducing sugar. However, reducing the base and phosphorus fertilizer application by 25 % improved multiple indicators of tobacco leaf quality, aligning better with high-quality tobacco standards in the region.