Potassium (K) is essential for regulating plant growth and mediating abiotic stress responses. Elucidating the biological mechanism underlying plant responses to K-deficiency is crucial for breeding new cultivars with improved K uptake and K utilization efficiency. In this study, we evaluated the extent of the genetic variation among 543 wheat accessions differing in K-deficiency tolerance at the seedling and adult plant stages. Two accessions, KN9204 and BN207, were identified as extremely tolerant and sensitive to K-deficiency, respectively. The accessions were exposed to normal and K-deficient conditions, after which their roots underwent ionomic, transcriptomic, and metabolomic analyses. Under K-deficient conditions, KN9204 exhibited stronger root growth and maintained higher K concentrations than BN207. Moreover, 19,440 transcripts and 162 metabolites were differentially abundant in the roots of both accessions according to transcriptomic and metabolomic analyses. An integrated analysis of gene expression and metabolite profiles revealed that substantially more genes, including those related to ion homeostasis, cellular reactive oxygen species homeostasis, and the glutamate metabolic pathway, were up-regulated in KN9204 than in BN207 in response to low-K stress. Accordingly, these candidate genes have unique regulatory roles affecting plant K-starvation tolerance. These findings may be useful for further clarifying the molecular changes underlying wheat root adaptations to K deprivation.

Potassium (K) is the second most important plant nutritional element and is used for numerous physiological processes. We established an eight-year experiment comparing the effects of five K fertilization treatments (0, 48, 84, 120 and 156 kg K ha⁻¹) on crop yield, K use efficiency and soil apparent K balance under the maize–wheat rotation system in the North China Plain. The highest maize and wheat yields were achieved in the K₁₂₀ treatment, increasing by up to 16.7% and 25.1%, respectively. The increase in grain yield and K agronomic efficiency (AE_K) with K application was greater in wheat than in maize. The K recovery efficiency (RE_K) and K accumulative recovery efficiency (ARE) significantly decreased with the increase in K fertilization in the maize and wheat seasons. However, the soil apparent K balance and soil available K content increased; the former was deficiency (−24.3 kg ha⁻¹ yr⁻¹) in the K₀ treatment, but the latter did not decrease significantly compared with that in the initial year of the experiment. The soil available K content increased by 10.9 mg kg⁻¹ per 100 kg ha⁻¹. In conclusion, the yield response to K fertilization was greater in wheat than in maize and alleviated soil K depletion, but the K fertilizer efficiency was lower. We believed that K fertilizer can be increased moderately in the wheat season and decreased in the maize season.

Late stage nitrogen (N) applications following basic fertilization are commonly used to ensure grain yield and increase grain protein content in wheat. Split N applications at the late growth stage of wheat are an effective measure to improve N absorption and transport and thus increase grain protein content. However, whether split N applications can alleviate the decrease in grain protein content induced by elevated atmospheric CO₂ concentrations (e[CO₂]) remains unclear. In the present study, a free-air CO₂ enrichment system was used to investigate the effects of split N applications (at booting or anthesis) on grain yield, N utilization, protein content, and the composition of wheat under atmospheric (ACO₂; 400 ± 15 ppm) and elevated CO₂ concentrations (ECO₂; 600 ± 15 ppm). The results showed that wheat grain yield and grain N uptake increased by 5.0% (being grains per ear by 3.0%, 1000-grain weight by 2.0%, and harvest index by 1.6%) and 4.3%, respectively, whereas grain protein content decreased by 2.3% under ECO₂ conditions. Although the negative effect of e[CO₂] on grain protein content was not alleviated by split N applications, gluten protein content was enhanced due to the alteration of N distribution in different protein fractions (albumins, globulins, gliadins, and glutenins). Compared to that without split N applications, the gluten content of wheat grains increased by 4.2% and 4.5% when late stage N was applied at the booting stage under ACO₂ and anthesis under ECO₂ conditions, respectively. The results indicate that rational handling of N fertilizers may be a promising approach to coordinating grain yield and quality under the effects of future climate change. However, compared to ACO₂ conditions, the key timing for improving grain quality by split N applications should be postponed from the booting stage to anthesis under e[CO₂] conditions.

Given the pressing global food security crisis and climate change-induced constraints on agricultural productivity, crop rotation proves critical for boosting yield and grain quality of winter wheat (Triticum aestivum) alongside ameliorating soil quality. However, the legacy effect of different preceding crops on synergistic increments of wheat productivity and soil fertility remains to be fully clarified. Five different preceding crop–winter wheat rotations were conducted in a field experiment established in Huanghua, China. Maize (Zea mays), sorghum (Sorghum bicolor), and millet (Setaria italica) were designated as preceding gramineous crops, and soybean (Glycine max) and mung bean (Vigna radiata) were assigned as preceding legume crops. Grain yield, protein fraction, and soil nutrients were measured to elucidate the legacy effect of the preceding crops on the subsequent winter wheat. Leguminous predecessors significantly evaluated the grain yield of winter wheat compared to gramineous predecessors, particularly that the mung–winter wheat rotation (Mun-W) was 11.56% higher than that of the maize–winter wheat rotation (Mai-W). This rising yield was attributed to the increase of 4.05% in spike number per hectare and 14.31% in kernel number per spike. The Mun-W facilitated the highest gluten protein content (8.22%) in winter wheat among five treatments, which was 6.06% higher than that in the sorghum–winter wheat system. Soil organic matter (SOM) showed an advantage in legume–winter wheat rotations (Leg-Ws) compared to gramineous crop–winter wheat systems (Gra-Ws). Notably among these, the Mun-W significantly enhanced SOM content by 0.99% relative to the Mai-W. The soybean–winter wheat system decreased soil pH by 0.36 compared to the Mai-W system. Coupling coordination degree (CCD) and co-benefit index (CBI) in the Leg-Ws exhibited significant superiority of 62.41% and 42.22% over the Gra-Ws, respectively, and the Mun-W attained maximum CCD by 0.84 and CBI by 0.77. From a multi-objective assessment perspective of the legacy effect of the preceding crops, legume-based rotations facilitate synergistic improvements of yield, protein quality, and soil nutrients in winter wheat.

Processes in the leaf apoplast are relevant for development, cell wall rheological properties, plant nutrition, sink-source portioning, microbe-host plant-interactions or intercellular information exchange and signaling and are therefore regulated or influenced by the composition of the leaf apoplastic solute. In contrast to the traditional methods for the extraction of apoplastic solutes that are more or less destructive, we propose a new method that allows extraction of leaf apoplastic solutes (i) non-invasively and, thus, (ii) over time. Moreover, the method has (iii) a high spatial resolution that allows identification of solute-microdomains in the leaf apoplast. The method was established for Arabidopsis thaliana and Vicia faba leaves but should also be applicable to other plants species with similar leaf morphologies. It is based on the infiltration of an aqueous extraction solution into the apoplast followed by its recovery seconds later, both through the stomata. By this, the apoplast (and its solutes) of an identical leaf can be sampled on successive days with negligible symplastic contamination. A spatiotemporal mapping of leaf apoplastic ion and metabolite patterns within the identical leaf opens a window of opportunity for understanding apoplast biology. As for example, the existence of apoplastic abscisic acid gradients within a leaf in response to salinity was witnessed in this study, as was the unsuspected accumulation of kaempferol glycosides in the leaf apoplast. The presented method is relevant for plant developmental biologists, phytopathologists, plant physiologists, plant nutritionists and others that need to integrate apoplast biology into their research approaches.

Late-season foliar nitrogen (N) application is widely employed to improve wheat grain yield and protein concentration, particularly during later growth stages when root activity declines and N uptake becomes less efficient. However, the reported effects of foliar N application on grain yield and the quality of wheat remain inconsistent. This meta-analysis, based on 51 field trials encompassing 1498 observations, quantitatively evaluates the impact of late-season foliar N application on wheat yield and protein concentration. The results demonstrate that late-season foliar N application significantly enhances both grain yield (+4.1%) and protein concentration (+5.9%) compared to control treatments. Notably, split foliar N application primarily increased protein concentration (+6.3%), whereas late-season N supplementation enhanced both yield (+3.4%) and protein concentration (+6.0%). Subgroup analyses reveal that the effectiveness of foliar N application is influenced by N management practices. Split foliar N application significantly increased both yield and protein concentration at N rates of 101–200 kg N/ha, whereas late-season N supplementation was beneficial only at higher N rates (≥200 kg N/ha). Moreover, the timing of foliar N application played a crucial role: application at anthesis resulted in the greatest increases in both yield (+5.3%) and protein concentration (+5.8%), while applications at booting or post-anthesis stages primarily increased protein concentration with minimal yield effects. Additionally, late-season foliar N application mitigated the conventional negative correlation between wheat yield and protein concentration, particularly when applied as a split N strategy, allowing for improved grain quality without reducing yield potential. This study highlights the importance of optimizing foliar N timing, the method, and N rate to maximize both wheat yield and quality while improving N use efficiency.