Introduction: Extensive research has been conducted on water- limited irrigation strategies and yield component variations in winter wheat (Triticum aestivum L.). However, limited understanding exists regarding the nuanced responses of winter wheat canopies and gene expressions to rehydration events. Methods: A field investigation was carried out throughout the winter wheat growing season from 2018 to 2020. Four distinct irrigation schedules were implemented, with water supplementation carefully synchronized with irrigation timing to match the appearance of the third, fourth, fifth, and sixth leaves. Further investigation into the molecular mechanisms of winter wheat rehydration using RNA- seq and ultra- performance liquid chromatography- mass spectrometry (UPLC- MS). Results and discussion: Our findings show that delayed rehydration results in reduced total water use across all treatment groups during the reproductive growth period, especially from jointing to flowering. A consistent pattern of reduction was observed in leaf area index (LAI), biomass at maturity (BAM), and plant height as rehydration was progressively delayed. The analysis found no statistically significant differences in phenotypic traits among winter wheat at the four- leaf stage before irrigation. In contrast, delaying rehydration until the fifth- leaf stage in spring had a noticeable impact on phenotypic traits. Implementing delayed rehydration at the four- leaf stage increased grain yield by 8. 31% to 51.23. 23%, mainly through three key yield components: more spikes, optimized grains per spike, and higher 1000- grain weight. Interestingly, the increase in 1000- grain weight was inversely related to total grain quantity after postponed rehydration. Transcriptomic and metabolomic analyses showed that postponed rehydration was associated with flavonoid biosynthesis pathways. Notably, the gene related to dihydrokaempferol- known to be involved in phenylpropanoid, flavonol, and flavone biosynthesis- showed a significant positive correlation with naringenin, chrysin, taxifolin, and prunin. Chlorogenic acid and luteolin also exhibited strong positive correlations with various agronomic traits, such as kernel number and 1000- grain weight. These results suggest the presence of a potential molecular regulator at a critical developmental stage, offering new insights into the mechanisms influencing crop yield under water- restricted irrigation conditions.

Delayed sowing frequently occurs in the North China Plain (NCP), restricting pre-winter population establishment and reducing grain yield. To determine whether narrow row spacing can alleviate yield loss under delayed sowing by improving the pre-winter stem and tiller basis, a randomized block experiment with two row spacings and four sowing-date regimes with adjusted planting density was conducted from 2021 to 2024. Yield components, pre-winter stem and tiller number and quality, and anatomical and physiological traits of the main-stem base and tiller nodes were measured. The results showed that 7.5 cm narrow row spacing (R2) increased tiller occurrence and improved hormonal balance and non-structural carbohydrate accumulation in the main-stem base and tiller nodes, and was associated with enhanced anatomical structural integrity and pre-winter stem and tiller quality. R2 increased final spike number, grain number per spike, thousand-grain weight, and grain yield by an average of 2.8%, 8.6%, 3.9%, and 10.7%, respectively, with the greatest yield increase under moderately delayed sowing (S2, 17.7%), and structural equation modeling (SEM) supported this possible yield-increasing pathway (χ²/df = 1.38, GFI = 0.90).These results provide a theoretical basis and technical reference for stabilizing and increasing yield in delayed-sown winter wheat in the NCP.

In the North China Plain (NCP), wind and rain during the grain-filling period of winter wheat can cause lodging. The second basal internode (I2), a key load-bearing structure, plays a central role in yield stability. This study, under a constant nitrogen (N) application rate of 270 kg ha⁻¹, aimed to clarify how nitrogen basal-to-topdressing ratios regulate I2 characteristics to balance lodging resistance and yield increase. Field experiments were conducted across two seasons with three cultivars and three nitrogen split ratios (5:5, CK; 3:7, N1; and 7:3, N2). Dynamic measurements of I2 mechanical properties, morphology, anatomy, and composition were taken, and structural equation modeling (SEM) was used for analysis. Results showed that the culm lodging resistance index (CLRI) decreased by 41.8% from flowering to milk stage under all treatments, with CLRI at the milk stage of lodging treatments between 0.11 and 0.15. SEM supported a composition–structure–lodging resistance–yield chain, with CLRI as the key mediator. The N1 treatment significantly improved CLRI at all stages and increased yield by 12.2% compared to CK, making it a recommended nitrogen strategy for improving both yield and lodging resistance. These findings provide agronomically applicable nitrogen management guidelines for high-yield winter wheat systems.