The rising temperatures and changes in precipitation due to climate change have significantly impacted agricultural production. Evaluating the effects of climate change on rice production is crucial for improving rice cultivation techniques and ensuring food security. It is essential to comprehensively examine the climatic, spatial, and temporal variations during the duration of crop production. Previous research has mainly focused on different rice planting areas, rice types, and various growth stages of rice. However, more research is needed on the climatic changes during the crop-growing season in specific regions. Therefore, this study compiled complete daily meteorological data from 37 meteorological stations in Hunan Province from 1961 to 2020. The period from 1961 to 2020 was divided into three segments: 1961–1980 (a), 1981–2000 (b), and 2001–2020 (c), to analyze the characteristics of agricultural climate resource changes during different growth stages of early-season rice in Hunan Province. Results show that the heat resources were significantly increased (accumulated temperature growth rate of 43.36 °C/10a), the sunshine resources were decreased by −14.60 h/10a, and the precipitation resources were slightly increased by 6.85 mm/10a. The increase in heat resources mainly occurs during the vegetative growth stage of early-season rice. Additionally, the high-value regions of heat resources and precipitation in period c are 97.8% and 34.2% higher than the average values of periods a and b, respectively. In contrast, the regions with high sunshine hours significantly decreased in period c compared to periods a and b. In summary, the heat, sunshine, and water resources in the central and eastern regions of Hunan Province increase simultaneously, and appropriate cultivation measures should be adopted in the future to improve the yield and resource utilization efficiency of early-season rice in a double-cropping system.

The utilization of saline–alkali land for rice cultivation is critical for global food security. However, most existing studies on rice salt tolerance focus on the seedling stage, with limited insights into tolerance mechanisms during reproductive growth, particularly at the panicle initiation stage (PI). Leveraging precision salinity-control facilities, this study imposed four salt stress gradients (0, 3, 5, and 7‰) to dissect the differential response mechanisms of six rice varieties (YXYZ: Yuxiangyouzhan, JLY3261: Jingliangyou3261, SLY91: Shuangliangyou91, SLY138: Shuangliangyou138, HLYYHSM: Hualiangyouyuehesimiao, and SLY11:Shuangliangyou111) during PI. The results revealed that increasing salinity significantly reduced tiller number (13.14–68.04%), leaf area index (18.58–57.99%), canopy light interception rate (11.91–44.08%), and net photosynthetic rate (2.63–52.42%) (p < 0.001), accompanied by reactive oxygen species (ROS)-induced membrane lipid peroxidation. Integrative analysis of field phenotypic and physiological indices revealed distinct adaptation strategies: JLY3261 rapidly activated antioxidant enzymes under 3‰ salinity, alleviating lipid peroxidation (no significant difference in H₂O₂ or malondialdehyde content compared to 0‰ salinity) and maintaining tillering and aboveground biomass. SLY91 tolerated 7‰ salinity via CAT/POD-mediated lipid peroxide degradation, with H₂O₂ and malondialdehyde contents increasing initially but decreasing with escalating stress. These findings highlight genotype-specific antioxidant strategies underlying salt-tolerance mechanisms and the critical need for integrating phenomics–physiological assessments at reproductive stages into salt-tolerance breeding pipelines.

Salinity stress severely limits rice productivity and grain quality worldwide. Although exogenous foliar application of titanium dioxide nanoparticles (nano-TiO₂) has been reported to enhance crop stress tolerance, its regulatory roles in yield formation and grain quality in rice varieties with differing salt tolerance are not well understood. In the present study, two contrasting rice varieties, viz., Jingliangyou 3261 (JLY3261; salt-tolerant) and Yuxiangyouzhan (YXYZ; salt-sensitive), were applied with five nano-TiO₂ foliar application treatments—viz., CK: water spray; Ti1: 15 mg L⁻¹; Ti2: 30 mg L⁻¹; Ti3: 45 mg L⁻¹; and Ti4: 60 mg L⁻¹—at the jointing and panicle initiation stages. Plants were irrigated with 0.3% saltwater to simulate salt stress. The results showed that Ti2 and Ti3 treatments led to 8.59% and 14.80% increases in grain yield in JLY3261 and YXYZ, respectively, compared with CK. Ti2 and Ti3 treatments significantly increased the leaf area index, net photosynthetic rate, and aboveground biomass of both varieties at the heading stage. Meanwhile, the activities of antioxidant enzymes such as superoxide dismutase and peroxidase, as well as nitrogen metabolism enzymes including nitrate reductase and glutamine synthetase, were improved with a substantial reduction in malondialdehyde contents. Application of nano-TiO₂ upregulated the expression of ion transport-related genes such as OsSOSs, OsNHXs and OsHKTs, thus improving leaf K⁺ accumulation and reducing Na⁺ content to optimize the K⁺/Na⁺ ratio. In addition, Ti2 and Ti3 treatments improved the milled rice rate, head rice rate, and protein content, while they decreased the chalkiness degree of both rice cultivars. Principal component analysis showed that the aboveground biomass at the heading stage was a core evaluation index for both varieties. Overall, foliar application of 30–45 mg L⁻¹ nano-TiO₂ was found to be effective regarding growth and yield improvement in rice under saline conditions. This study provides a theoretical basis for agro-management strategies for rice cultivation in saline–alkaline soils.

In the context of global climate change, the co-occurrence of salt and heat stress represents a major constraint to rice production, resulting in greater yield penalties than either stress alone. This study aimed to assess the effects of salt and heat stress on oxidative homeostasis, photosynthetic performance, carbon (C)–nitrogen (N) metabolism, and rice yield. The experiment comprised four treatments, i.e., control (CK), salt (irrigation with 3.9 dS m⁻¹ NaCl solution), heat (exposure to 36 °C/30 °C day/night for 5 days at panicle initiation), and combined salt + heat stress. Results showed that combined stress enhanced reactive oxygen species (ROS) accumulation (i.e., H₂O₂ content and O₂⁻ contents were 1.3 and 1.5 times higher than CK), and the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were increased by 64.6%, 69.5%, and 74.8% higher than CK. At the molecular level, salt + heat stress upregulated antioxidant defense-related genes, i.e., OsAPX2, OsSODCC1, and OsAPX1, while significantly downregulated ion homeostasis-related genes, i.e., OsSOSs, OsHKT1;3, OsHKT1;5, and OsNHX4, and photosynthesis-related genes, i.e., Ospsbo, OsRbcS2, and OsRbcS3, compared with CK. Furthermore, salt + heat stress reduced the activities of C-metabolism enzymes (sucrose phosphate synthase, sucrose synthase, and starch synthase) and N-metabolism enzymes (nitrate reductase, glutamine synthetase, and glutamate synthase), leading to 34.3% and 18.6% lower stem-sheath non-structural carbohydrate accumulation in stem sheath and its translocation rate, respectively, while total N accumulation decreased by 42.9%, as compared with CK. Ultimately, these cascading effects inhibited panicle development and reduced yield. The findings provide a theoretical basis for improving rice tolerance to combined abiotic stresses by targeting oxidative stress mitigation, photosynthetic protection, and key stress-responsive gene regulation.

Against the backdrop of global population and food demand growth, the development of ratoon rice is conducive to increasing food production and ensuring food security. Applying agricultural biotechnology and plant growth regulator to ratoon rice production is a key measure to promote the development of green agriculture and address the challenges of global food security. A total of 4 treatments were set up in this study: T1 (regulator); T2 (biological agent made from plant materials); T3 (microbial agent); and control (CK). The results showed that T3 up-regulated many key genes (OsHsfC1b, OsCNGC16, OsOSM1, OsSAPK9, and DTH2, etc.) and metabolites (spermine, citric acid, riboflavin, and shikimic acid). T2 was found to up-regulate key genes OsAPT2, OsZIP8, OsCIPK14, OsCIPK7, OsPR4c, and OsVIT2, and its regulatory effects involved carbohydrate, lipid, and amino acid metabolism, etc. In addition, the two biological agents and one regulator significantly increased the accumulation of stem dry matter and yield in the first season. T1, T2, and T3 significantly increased the final regenerative capacity of Yongyou4949 at D5 (fifth node from the top); T1 and T2 significantly increased the maximum and final regenerative capacities of Shuangliangyou138 at D5. This study provided guidance for developing more effective agricultural management strategies, which is conducive to the sustainable development of agriculture.