Nitrogen (N) supplementation is essential to the yield and quality of bread wheat (Triticum aestivum L.). The impact of N-deficiency on wheat at the seedling stage has been previously reported, but the impact of distinct N regimes applied at the seedling stage with continuous application on filling and maturing wheat grains is lesser known, despite the filling stage being critical for final grain yield and flour quality. Here, we compared phenotype characteristics such as grain yield, grain protein and sugar quality, plant growth, leaf photosynthesis of wheat under N-deficient and N-sufficient conditions imposed prior to sowing (120 kg/hm²) and in the jointing stage (120 kg/hm²), and then evaluated the effects of this continued stress through RNA-seq and GC-MS metabolomics profiling of grain at the mid-filling stage. The results showed that except for an increase in grain size and weight, and in the content of total sugar, starch, and fiber in bran fraction and white flour, the other metrics were all decreased under N-deficiency conditions. A total of 761 differentially expressed genes (DEGs) and 77 differentially accumulated metabolites (DAMs) were identified. Under N-deficiency, 51 down-regulated DEGs were involved in the process of impeding chlorophyll synthesis, chloroplast development, light harvesting, and electron transfer functions of photosystem, which resulted in the SPAD and Pn value decreased by 32 and 15.2% compared with N-sufficiency, inhibited photosynthesis. Twenty-four DEGs implicated the inhibition of amino acids synthesis and protein transport, in agreement with a 17–42% reduction in ornithine, cysteine, aspartate, and tyrosine from metabolome, and an 18.6% reduction in grain protein content. However, 14 DEGs were implicated in promoting sugar accumulation in the cell wall and another six DEGs also enhanced cell wall synthesis, which significantly increased fiber content in the endosperm and likely contributed to increasing the thousands-grain weight (TGW). Moreover, RNA-seq profiling suggested that wheat grain can improve the capacity of DNA repair, iron uptake, disease and abiotic stress resistance, and oxidative stress scavenging through increasing the content levels of anthocyanin, flavonoid, GABA, galactose, and glucose under N-deficiency condition. This study identified candidate genes and metabolites related to low N adaption and tolerance that may provide new insights into a comprehensive understanding of the genotype-specific differences in performance under N-deficiency conditions.

Abscisic acid (ABA) plays a physiological role in regulating the heat tolerance of plants and maintaining crop productivity under high-temperature stress. Appropriate cultivation techniques can regulate endogenous ABA and help farmers improve food production under high-temperature stress. Here, the physiological basis for ABA-induced heat tolerance in crops is reviewed. High-temperature stress stimulates ABA, which reduces stomatal opening and promotes root growth. The root system absorbs water to maintain the water status, thus allowing the plant to maintain physiological activities under high-temperature stress. ABA plays a synergistic role with nicotinamide adenine dinucleotide biosynthesis to improve the thermal stability of the cell membrane, maintain a dynamic balance between material and energy, and reduce the negative effects of high-temperature stress on kernel number and kernel weight. Cultivation and tillage techniques adapted to high-temperature stress, such as adjustment of sowing time, application of plant growth regulators and fertilizers, and the use of irrigation, subsoiling and heat acclimation, and the mechanisms by which they improve crop heat tolerance, are also reviewed. The results of the studies reviewed here will help researchers develop techniques for cultivating food crops under heat stress and apply them to food-production fields to improve crop productivity.

Heat stress negatively affects wheat production in many regions of the world. At present, sensitivity to heat stress remains one of the least understood aspects of wheat genetics and breeding, and measures for preventing heat stress are understudied. In this study, we used three cultivars of winter wheat (GY2018, SL02-1 and SY20) to evaluate the effect of heat stress at different days after anthesis (DAA) on yield and quality. Heat stability of the cultivars were analyzed and evaluated for the effects of two kinds of regulators on wheat under heat stress conditions. Heat treatment at 7 DAA led to the most substantial reduction in yield while GY2018 had the best heat stability with respect to yield, and demonstrated the most positive effects on several quality traits including protein content, sedimentation volume and glutenin and gliadin contents. Heat treatment at 14 DAA had the least reduction in yield, while SY20 had the best heat stability with respect to yield and heat treatment had minimal effects on quality. Heat treatment at 21 DAA had only a limited effect on yield, while SL02-1 had the best heat stability with respect to yield, but it showed the most negative effects on quality. Stable time at 14 DAA and protein content at 21 DAA can be used as indicators for detecting the stability of quality under heat stress. Among the three studied cultivars, SY20 was the most sensitive to heat stress with the stable time decreasing from 26.4 to 9.1 min, a higher sedimentation volume at 7 DAA, and a lower γ-gliadin content which increased 2.4-fold under high-temperature treatment. The addition of various regulators had different effects: potassium dihydrogen phosphate (KDP) was more protective of yield with heat stress at 7 DAA, while Duntianbao (DTB) had better effects on quality with heat stress at 21 DAA.

Pre-flowering total dry matter remobilization (PTDR) and post-flowering photosynthetic accumulation (PTPA) are critical for grain-filling under abiotic stress, yet their temporal dynamics and organ-specific contributions under combined high temperature (HT) and drought stress (DS) remain poorly understood. Through a two-year field study (2021–2023) with two wheat cultivars (Zhongmai36 and Jimai22), we investigated yield components, PTDR-PTPA coordination, and grain-filling dynamics under HT, DS, and combined drought-heat stress (DHS). The results demonstrated that stress treatments significantly reduced yield by 14.1–33.3% (Zhongmai36) and 14.9–29.5% (Jimai22), driven by declines in grain numbers per spike (7.0–18.4%) and 1000-grains weight (5.0–17.5%). Random Forest analysis revealed the contribution of 1000-grains weight to the yield variation under all stresses amounts to 55.1–59.1%, while grain numbers per spike dominated 56.1–70.3% for Jimai22 under DS and DHS. Additionally, pre-flowering total dry matter remobilization (PTDR) increased by 18.6–21.5% under DHS due to enhanced contributions from the stem-sheath and leaf, partially mitigating yield losses. However, post-flowering photosynthetic accumulation (PTPA) decreased by 7.5–50.8%, with the most severe reductions under DHS. Meanwhile, the PTDR/PTPA ratio rose significantly under DHS, highlighting compensatory remobilization under combined stresses. The timing and contribution of dry matter remobilization varied across organs and stress conditions. The stem-sheath contributions peaked at 10–20 days after stress (DAS) under HT and DS, while leaf remobilization occurred earlier (0–10 DAS). Cultivar-specific responses were evident. The Zhongmai36 showed greater drought tolerance but higher HT sensitivity, whereas Jimai22 prioritized maintaining grains per spike (GNS) under DHS, reflecting divergent adaptation strategies to concurrent stresses. These findings underscore the importance of breeding strategies targeting organ-specific remobilization efficiency and photosynthetic retention during grain-filling are critical for climate-resilient wheat production.