The current research was aimed to study the effects of different land use types (LUT) and soil depth (SD) on soil enzyme activity, metal content, and soil fungi in the karst area. Soil samples with depths of 0–20 cm and 20–40 cm were collected from different land types, including grassland, forest, Zanthoxylum planispinum land, Hylocereus spp. land and Zea mays land. The metal content and enzyme activity of the samples were determined, and the soil fungi were sequenced. The results showed that LUT had a significant effect on the contents of soil K, Mg, Fe, Cu and Cr; LUT and SD significantly affected the activities of invertase, urease, alkaline phosphatase and catalase. In addition, Shannon and Chao1 index of soil fungal community was affected by different land use types and soil depths. Ascomycota, Basidiomycota and Mortierellomycota were the dominant phyla at 0–20 cm and 20–40 cm soil depths in five different land types. Land use led to significant changes in soil fungal structure, while soil depth had no significant effect on soil fungal structure, probably because the small-scale environmental changes in karst areas were not the dominant factor in changing the structure of fungal communities. Additionally, metal element content and enzyme activity were related to different soil fungal communities. In conclusion, soil mineral elements content, enzyme activity, and soil fungal community in the karst area were strongly affected by land use types and soil depths. This study provides a theoretical basis for rational land use and ecological restoration in karst areas.

Climate change has resulted in frequent heavy and prolonged rainfall events that exacerbate waterlogging stress, leading to the death of certain alpine Rhododendron trees. To shed light on the physiological and molecular mechanisms behind waterlogging stress in woody Rhododendron trees, we conducted a study of Rhododendron delavayi, a well-known alpine flower species. Specifically, we investigated the physiological and molecular changes that occurred in leaves of R. delavayi subjected to 30 days of waterlogging stress (WS30d), as well as subsequent post-waterlogging recovery period of 10 days (WS30d-R10d). Our findings reveal that waterlogging stress causes a significant reduction in CO₂ assimilation rate, stomatal conductance, transpiration rate, and maximum photochemical efficiency of PSII (Fv/Fm) in the WS30d leaves, by 91.2%, 95.3%, 93.3%, and 8.4%, respectively, when compared to the control leaves. Furthermore, the chlorophyll a and total chlorophyll content in the WS30d leaves decreased by 13.5% and 16.6%, respectively. Both WS30d and WS30d-R10d leaves exhibited excessive H₂O₂ accumulation, with a corresponding decrease in lignin content in the WS30d-R10d leaves. At the molecular level, purine metabolism, glutathione metabolism, photosynthesis, and photosynthesis-antenna protein pathways were found to be primarily involved in WS30d leaves, whereas phenylpropanoid biosynthesis, fatty acid metabolism, fatty acid biosynthesis, fatty acid elongation, and cutin, suberin, and wax biosynthesis pathways were significantly enriched in WS30d-R10d leaves. Additionally, both WS30d and WS30d-R10d leaves displayed a build-up of sugars. Overall, our integrated transcriptomic, physiological, and metabolomic analysis demonstrated that R. delavayi is susceptible to waterlogging stress, which causes irreversible detrimental effects on both its physiological and molecular aspects, hence compromising the tree’s ability to fully recover, even under normal growth conditions.

Rhododendron liliiflorum H. Lév., with white outer edges and yellow inner edges of petals, is an ornamental flower that originated in China. In this study, we analysed the white (W) and yellow (Y) parts of R. liliiflorum flowers by RNA sequencing. Then, unigene assembly, unigene annotation, and classification of Eukaryotic Orthologous Groups (KOGs) were performed. Gene ontology (GO) classification and pathway enrichment analysis for unigenes were also conducted. A total of 219,221 transcripts and 180,677 unigenes of R. liliiflorum were obtained from 48.52 Gb of clean reads. Differentially expressed gene (DEG) analysis indicated that 2310 unigenes were upregulated and 3062 were downregulated in W vs. Y. Thirty-six of these DEGs were involved in the flavonoid biosynthesis pathway. Pathway enrichment analysis showed that DEGs were significantly enriched in phenylpropanoid, flavonoid, and isoflavone biosynthesis. The expression of dihydroflavonol-4-reductase (DFR) and chalcone synthase (CHS) may affect differences in R. liliiflorum flower colour. The findings on flavonoid biosynthesis and other related genes in this study will provide guidance for exploring the mechanism of flower colour formation in Rhododendron.

With the development of industrial activities and the agricultural and mining industries, farmland soils are facing serious problems related to heavy metal contamination, especially cadmium (Cd) and arsenic (As) contamination. In this study, two industrial by-products, phosphogypsum (PG) and red mud (RM), were modified by lanthanum (La) impregnation to form a new composite (L-PR) to investigate the adsorption performance of Cd(II)/As(V) in both single and binary systems. The adsorption mechanisms of Cd(II)/As(V) on L-PR were analyzed using SEM, XRD, FTIR, and XPS. The passivation effect of L-PR on the Cd-As composite contaminated soil was confirmed through a soil cultivation experiment. The adsorption experiments revealed that L-PR showed superior adsorption capabilities for Cd(II) and As(V) compared to PG and RM. Additionally, L-PR was found to be less affected by changes in pH. The kinetic studies indicated that Cd(II) and As(V) adsorption by L-PR followed the second-order kinetic model most accurately. Isothermal adsorption experiments revealed that the adsorption of Cd(II) by L-PR was more in accordance with the Freundlich model, while As(V) was more in accordance with the Langmuir model. The mechanisms of Cd(II) and As(V) adsorption on L-PR involved electrostatic attraction, ion exchange, complexation, and precipitation. The adsorption of Cd(II) is dominated by complexation and precipitation, and the adsorption of As(V) is dominated by ion exchange and complexation. Soil cultivation experiments showed that L-PR significantly reduced the available Cd and As concentrations in soil by 86.01% and 27.80%, respectively, and it could induce the transformation of non-stable Cd(II)/As(V) to the more stable residual. In summary, L-PR exhibits facile preparation, excellent adsorption performance, and is capable of simultaneously removing Cd(II) and As(V) from aqueous solutions while immobilizing these contaminants in soil. These remarkable attributes made it a highly promising alternative for the simultaneous treatment of various toxic metal contaminants.

The petal blight disease of alpine Rhododendron severely impacts the ornamental and economic values of Rhododendron. Plant secondary metabolites play a crucial role in resisting pathogenic fungi, yet research on metabolites in alpine Rhododendron petals that confer resistance to pathogenic fungi is limited. In the present study, the secondary metabolites in Rhododendron delavayi, R. agastum, and R. irroratum petals with anti-pathogenic activity were screened through disease index analysis, metabolomic detection, the mycelial growth rate, and metabolite spraying experiments. Disease index analysis revealed that R. delavayi petals exhibited the strongest disease resistance, while R. agastum showed the weakest, both under natural and experimental conditions. UHPLC-QTOF-MS/MS analysis identified 355 and 274 putative metabolites in positive and negative ion modes, respectively. The further antifungal analysis of differentially accumulated baicalein, diosmetin, and naringenin showed their half-inhibitory concentrations (IC50) against Neopestalotiopsis clavispora to be 5000 mg/L, 5000 mg/L, and 1000 mg/L, respectively. Spraying exogenous baicalein, diosmetin, and naringenin significantly alleviated petal blight disease caused by N. clavispora infection in alpine Rhododendron petals, with the inhibition rates exceeding 64%. This study suggests that the screened baicalein, diosmetin, and naringenin, particularly naringenin, can be recommended as inhibitory agents for preventing and controlling petal blight disease in alpine Rhododendron.

Complex interspecific relationships between parasites and their insect hosts involve multiple factors and are affected by their ecological and evolutionary context. A parasitoid Sclerodermus guani (Hymenoptera: Bethylidae) and an entomopathogenic fungus Beauveria bassiana (Hypocreales: Cordycipitaceae) shared the same host in nature, Monochamus alternatus (Coleoptera: Cerambycidae). They often encountered the semi-enclosed microhabitat of the host larvae or pupae. We tested the survival and reproduction of the parasitoid’s parent and its offspring fitness under different concentrations of B. bassiana suspension. The results show that S. guani parent females carrying higher concentrations of the pathogen shorten the pre-reproductive time and regulate their own fertility and their offspring’s survival and development. This minimal model of the interspecific interactions contains three dimensionless parameters, vulnerability (θ), dilution ratio (δ), and P_R, which were used to evaluate the mortality effect of the parasitoid S. guani on its host M. alternatus under the stress of the entomopathogenic fungus B. bassiana. We compared the infection and lethal effect of the fungus B. bassiana with different concentrations to the parasitoid S. guani and the host larvae M. alternatus. At higher concentrations of the pathogen, the parasitoid parent females shorten the pre-reproductive time and regulate their own fertility and their offspring’s survival and development. At moderate concentrations of the pathogen, however, the ability of the parasitoid to exploit the host is more flexible and efficient, possibly reflecting the potential interspecific interactions between the two parasites which were able to coexist and communicate with their hosts in ecological contexts (with a high overlap in time and space) and cause interspecific competition and intraguild predation.