Sen Li

Introduction: While climate change alters the balance of the terrestrial ecosystems, the impact on the soil bacterial community remains poorly understood. A field experiment was conducted to assess the effects of warming, drought, and their combination on the soil bacterial community at different growth stages of winter wheat. Methods: Four treatments were defined for this study: warming at 1.5°C combined with full irrigation (TWS) and deficit irrigation (TWD), then ambient temperature combined with full irrigation (TNS) and deficit irrigation (TND). Results: TWS, unlike TND, promoted nitrogen availability for plants and root exudation. The abundance and diversity of the bacterial community were more responsive to different climatic stresses at the jointing stage than at other growth stages. Chloroflexi , Firmicutes , and Bacteroidota were positively correlated with soil inorganic nitrogen, the root total organic carbon (TOC), and negatively correlated with available phosphorus (AP), available potassium (AK), soil organic carbon (SOC) under TND, while an opposite trend was observed with Actinobacteria and Proteobacteria . Furthermore, under TWS, Bacteroidota , unlike Actinobacteria , was positively correlated with NH ₄ ⁺ , NO ₃ ^- , TOC, and negatively correlated with AP, and SOC. The bacterial community network feature values were higher under TWD and lower under TNS. Conclusion: These results indicate that the sensitivity of the rhizosphere bacterial community to the different climatic stresses varies according to the growth stage, and that the community is particularly more responsive at the jointing stage than at the later stages.

Root morphology and uptake capacity are increasingly investigated as indicators of crop performance, yet their characterization remains challenging in laboratory. Soil or sand are opaque to most forms of radiation, while transparent medium fails to provide soil-relevant characteristics. Transparent soil (TS) is specifically designed to support root growth in the presence of air, water, and nutrients, enabling in situ root phenotyping. An indoor experiment was conducted, involving three growth mediums (natural soil, TS, hydroponics), two fibrous-root crop species (wheat, maize) and two taproot crop species (cotton, soybean), to evaluate the impact of TS on root morphology and water and nitrogen uptake of crops with different root types. Results showed that, compared with the average difference between hydroponics and natural soil, the average difference in root morphology and water and nitrogen uptake of maize between TS and natural soil was significantly decreased, as well as for cotton, soybeans, and wheat in turn. It was concluded that compared to those developed in hydroponics, the root developed in TS was significantly more similar to those developed in natural soil. Yet such similarity varied across crop species, with no clear correlation to root types. These findings provide a theoretical foundation for promoting the application of TS.

Transparent soil (TS) was specifically designed to support root growth in the presence of air, water, and nutrients and allowed the time-resolved phenotyping of roots in vivo. Nevertheless, it is imperative to further optimize the reagent cost of TS to enable its wider utilization. We substituted the costly Phytagel obtained from Sigma with two more economical alternatives, namely Biodee and Coolaber. TS beads from each brand were prepared using 12 different polymer concentrations and seven distinct crosslinker concentrations. A comprehensive assessment encompassing transparency, mechanical characteristics, particle size, porosity, and stability of TS was undertaken. Compared to the Sigma Phytagel brand, both Biodee and Coolaber significantly reduced the transparency and collapse stress of the TS they produced. Consequently, this led to a significant reduction in the allowable width and height of the growth box, although they could still simultaneously exceed 20 cm and 19 cm. There was no notable difference in porosity and stability among the TS samples prepared using the three Phytagel brands. Therefore, it is feasible to consider replacing the Phytagel brand to reduce TS production costs. This study quantified the differences in TS produced using three Phytagel brands at different prices that will better promote the application of TS to root phenotypes.

Grain development is a crucial determinant of yield and quality in bread wheat (Triticum aestivum L.). However, the regulatory mechanisms underlying wheat grain development remain elusive. Here we report how TaMADS29 interacts with TaNF-YB1 to synergistically regulate early grain development in bread wheat. The tamads29 mutants generated by CRISPR/Cas9 exhibited severe grain filling deficiency, coupled with excessive accumulation of reactive oxygen species (ROS) and abnormal programmed cell death that occurred in early developing grains, while overexpression of TaMADS29 increased grain width and 1,000-kernel weight. Further analysis revealed that TaMADS29 interacted directly with TaNF-YB1; null mutation in TaNF-YB1 caused grain developmental deficiency similar to tamads29 mutants. The regulatory complex composed of TaMADS29 and TaNF-YB1 exercises its possible function that inhibits the excessive accumulation of ROS by regulating the genes involved in chloroplast development and photosynthesis in early developing wheat grains and prevents nucellar projection degradation and endosperm cell death, facilitating transportation of nutrients into the endosperm and wholly filling of developing grains. Collectively, our work not only discloses the molecular mechanism of MADS-box and NF-Y TFs in facilitating bread wheat grain development, but also indicates that caryopsis chloroplast might be a central regulator of grain development rather than merely a photosynthesis organelle. More importantly, our work offers an innovative way to breed high-yield wheat cultivars by controlling the ROS level in developing grains.

In the North China Plain, drought usually occurs during the interval between wheat harvest and maize sowing in normal and dry years. The first irrigation for maize plays a critical role in guaranteeing seed germination and grain yields. Using experimental data from Xinxiang in 2019 and survey data of 641 farmers from the North China Plain in 2020, this study adopts a cost-benefit analysis method to investigate the impacts of irrigation time and well depths on farmers’ costs and benefits in maize production. The results showed that farms with well depth > 120 m accounted for 49% of total farms, especially in Hebei Province, and 38% wells had low water yield < 2.7 m³ kW⁻¹ h⁻¹. Delaying the time of the first irrigation made maize yields decline by up to 307 kg ha⁻¹ day⁻¹. Well depths increased irrigation costs and total maize production cost in an exponential manner, causing farmers’ benefits to decrease exponentially with well depths. With well depth > 180 m, the proportion of irrigation cost to total cost rose to 14%, whereas well depth > 230 m directly caused the farmers’ profits negative. A critical well depth of 230 m was put forward as the upper limit for farmers adopting maize planting in the NCP. The concept of ‘rotational irrigation strategy’ and suggestions of adopting drip irrigation, sprinkler irrigation, or hose-reel sprinkler irrigation were recommended to advance 6–8 days for the first irrigation period, compared with traditional flood irrigation.

To propose an appropriate nitrogen application mode and suitable drip irrigation lateral spacing, a field experiment was conducted during 2017–2018 and 2018–2019 growing seasons to quantify the different drip irrigation lateral spacings and nitrogen fertigation strategies effects on winter wheat growth, yield, and water use efficiency (WUE) in the North China Plain (NCP). The experiment consisted of three drip irrigation lateral spacing (LS) (40, 60, and 80 cm, referred to as D₄₀, D_60, and D₈₀ respectively) and three percentage splits of nitrogen application modes (NAM) (basal and top dressing application ratio as 50:50 (N_50:50), 25:75 (N_25:75), and 0:100 (N_0-100) respectively). The experimental findings depicted that yield and its components, and WUE were markedly affected by LS and NAM. Fertigation of winter wheat at N_25:75 NAM notably (P50:50 and N_0:100 in 2017–2018 and 2018–2019 growing seasons, respectively. LS D₄₀ appeared very fruitful in terms of soil moisture and nitrogen distribution, WUE, grain yield, and yield components than that of other LS levels. The maximum grain yield (8.73 and 9.40 t ha^-1) and WUE (1.70 and 1.95 kg m^-3) were obtained under D₄₀N_25:75 during both growing seasons, which mainly due to that all main yield components in D₄₀N_25:75 treatment, such as spikes per unit area, 1000-grain weight, and grains per spike were significantly higher as compared to other treatments. The outcomes of this research may provide a scientific basis of lateral spacing and nitrogen fertigation management for the production of drip-irrigated winter wheat in NCP.