Agronomy

Protein phosphatase 2Cs (PP2Cs) constitute a widespread family of signaling regulators in plants and play central roles in abscisic acid (ABA)-mediated stress signaling; however, the PP2C gene family has not yet been systematically identified and characterized in pea (Pisum sativum), a salt-sensitive legume crop. In this study, we identified 89 PsPP2C genes based on domain features and sequence homology. These genes are unevenly distributed across seven chromosomes and classified into ten subfamilies, providing a comparative framework for evaluating structural and regulatory diversification within the PsPP2C family. The encoded proteins vary substantially in length, physicochemical properties, and predicted subcellular localization, while most members contain the conserved PP2Cc catalytic domain. Intra- and interspecies homology analyses identified 19 duplicated gene pairs in pea and numerous orthologous relationships with several model plants; all reliable gene pairs exhibited Ka/Ks < 1, indicating pervasive purifying selection. PsPP2C genes also showed broad variation in exon number and intron phase, and their promoter regions contained diverse light-, hormone-, and stress-related cis-elements with heterogeneous positional patterns. Expression profiling across 11 tissues revealed pronounced tissue-specific differences, with generally higher transcript abundance in roots and seeds than in other tissues. Under salt treatment, approximately 20% of PsPP2C genes displayed concentration- or time-dependent transcriptional changes. Among them, PsPP2C67 and PsPP2C82—both belonging to the clade A PP2C subfamily—exhibited the most pronounced induction under high salinity and at early stress stages. Functional annotation indicated that these two genes are involved in ABA-related processes, including regulation of abscisic acid-activated signaling pathway, plant hormone signal transduction, and MAPK signaling pathway-plant. Collectively, this study provides a systematic characterization of the PsPP2C gene family, including its structural features, evolutionary patterns, and transcriptional responses to salt stress, thereby establishing a foundation for future functional investigations.

Exogenous carbon addition is widely regarded as an effective soil management strategy for rapidly increasing soil organic carbon, improving soil structure and function. However, a systematic comparison of the effects of diverse organic amendments on key soil attributes and processes is needed to inform their targeted application. We evaluated the impacts of seven organic amendments (biochar, organic fertilizer, corn straw, soybean straw, rapeseed straw, green manure, and carbon material) on a purple soil (Luvic Xerosols) in a pot experiment. The results showed that organic fertilizer and carbon material performed best in enhancing soil nutrient availability and promoting soil organic carbon content. Straw amendments promoted the formation of macro-aggregates. Green manure and straws enhanced carbon transformation-related β-glucosidase and cellobiohydrolase activities. Random Forest and structural equation modeling indicated that the organic amendments enhanced maize carbon sequestration capacity and biomass by improving aggregate stability and regulating the fungal community and by increasing nutrients and enhancing active carbon fractions. Green manure and organic fertilizer demonstrated the most significant agronomic effects. These findings provide guidelines for targeted organic amendment selection in purple soil regions.

Thallium (Tl) is a highly toxic trace metal of increasing concern in agricultural soils. This study investigated the uptake, accumulation, and tissue-level distribution of Tl(I) in rice (Oryza sativa L.) and wheat (Triticum aestivum L.) grown in three agricultural soils differing in soil pH and texture. In the seedling pot experiment (0–100 mg kg⁻¹ soil Tl), plant Tl concentrations increased dose-dependently, and were at least an order of magnitude lower in the alkaline soil than in the acidic soils. Bioaccumulation factors of roots and shoots generally exceeded unity and declined with increasing Tl dose in acidic soils, consistent with uptake saturation and physiological stress at high exposure. To elucidate how soil Tl speciation and pH regulate Tl availability, X-ray absorption spectroscopy (XAS) was used; it showed that Tl(I)—sorbed on illite was the predominant species in all soils (89–95%), with a minor fraction (5–11%) associated with non-specific adsorption. In maturity pots (5 mg kg⁻¹ soil Tl), both crops grown in the moderately acidic, coarse-textured soil translocated a small fraction of absorbed Tl to grains, with wheat and rice containing 0.24 and 0.10 mg kg⁻¹ Tl, respectively. Comparatively, plants in the more acidic soil failed to reach maturity, and grain Tl was not detected in the alkaline soil. LA-ICP-MS mapping revealed Tl enrichment in the bran and embryo of rice and in the crease, bran, and embryo of wheat, indicating that unpolished grains may pose higher dietary exposure risks than polished products. Overall, these findings demonstrate the key roles of soil pH and mineral composition in governing soil Tl availability and plant Tl uptake, whereas plant transport processes regulate grain Tl loading. In the absence of food-safety standards for Tl, the results of this study underscore the need to better understand and mitigate Tl transfer from contaminated soils into human food chains via cereal crops.