Wei Jiang

Orchard soils have distinct stratification heterogeneity, while the responses of soil organic carbon mineralization (essentially microbial-mediated decomposition of organic matter, mainly producing CO₂) and bacterial communities to exogenous carbon addition in different soil layers are still unclear. In this study, a laboratory incubation experiment was conducted to investigate the differences in soil organic carbon mineralization characteristics and bacterial communities between glucose addition and no-glucose addition treatments in three soil layers (N1: 0–20 cm, N2: 20–40 cm, N3: 40–60 cm) of hilly orchards. The results demonstrated that soil organic carbon mineralization rates in all layers generally declined with increasing incubation duration. At D3, compared with the CK group, glucose addition increased the soil organic carbon mineralization rate by 3.28-fold, 9.30-fold, and 15.03-fold in the N1, N2 and N3 soil layers, respectively. Cumulative organic carbon mineralization followed the order N1 > N2 > N3. Compared with the CK treatment, glucose addition increased C₀ by 65.62% and 203.97% in the N2 and N3 soil layers, respectively. Two-way ANOVA was applied to quantitatively separate and compare the contributions of carbon addition treatment, incubation time and soil layer, and Beta diversity analysis revealed that soil layer was the primary driving factor. Under glucose addition, the key microorganisms related to organic carbon mineralization varied across soil layers: Gemmatimonadota and Acidobacteriota may exert a negative effect on soil organic carbon mineralization in orchard soils, whereas copiotrophic taxa, including Sphingomonas and Bacteroidota, contributed more strongly to carbon mineralization. Our results highlight the pronounced impact of labile carbon input on soil organic carbon mineralization within different soil layers, and reveal associations between soil bacterial communities and organic carbon mineralization in orchard ecosystems.

The high-affinity potassium transporters (HKT) mediate K⁺-Na⁺ homeostasis in plants. However, the function of enhancing low-potassium tolerance in sweet potato [Ipomoea batatas (L.) Lam.] remains unrevealed. In this study, a novel HKT transporter homolog IbHKT-like gene was cloned from sweet potato, which was significantly induced by potassium deficiency stress. IbHKT-like overexpressing transgenic roots were obtained from a sweet potato cultivar Xuzishu8 using an Agrobacterium rhizogenes-mediated root transgenic system in vivo. Compared with the CK, whose root cells did not overexpress the IbHKT-like gene, overexpression of the IbHKT-like gene protected cell ultrastructure from damage, and transgenic root meristem cells had intact mitochondria, endoplasmic reticulum, and Golgi dictyosomes. The steady-state K⁺ influx increased by 2.2 times in transgenic root meristem cells. Overexpression of the IbHKT-like gene also improved potassium content in the whole plant, which increased by 63.8% compared with the CK plants. These results could imply that the IbHKT-like gene, as a high-affinity potassium transporter gene, may play an important role in potassium deficiency stress responses.