Background: Soil salinization is causing ecosystem degradation and crop yield reduction worldwide, and elucidation of the mechanism of salt-tolerant plants to improve crop yield is highly significant. Podocarpus macrophyllus is an ancient gymnosperm species with a unique environmental adaptation strategy that may be attributed to its lengthy evolutionary process. The present study investigated the physiological and molecular responses of P. macrophyllus plants to salt stress by analyzing its photosynthetic system and antioxidant enzyme activity. We also analyzed the differentially expressed genes (DEGs) in P. macrophyllus under salt stress using RNA sequencing and de novo transcriptome assembly. Results: Salt treatment significantly affected the photosynthetic system in P. macrophyllus seedlings, which decreased chlorophyll content, altered chloroplast ultrastructure, and reduced photosynthesis. The activities of antioxidant enzymes increased significantly following salt stress treatment. Transcriptome analysis showed that salt stress induced a large number of genes involved in multiple metabolic and biological regulation processes. The transcription levels of genes that mediate phytohormone transport or signaling were altered. K⁺ and Ca²⁺ transporter-encoding genes and the MYB transcription factor were upregulated under salt stress. However, the genes involved in cell wall biosynthesis and secondary metabolism were downregulated. Conclusion: Our research identified some important pathways and putative genes involved in salt tolerance in P. macrophyllus and provided clues for elucidating the mechanism of salt tolerance and the utilization of the salt tolerance genes of P. macrophyllus for crop improvement.

This study focused on assessing the impact of climate change on Cupressus funebris, one of the important endemic conifer species in China. The impact of fluctuations in temperature on the potential distribution and extinction risk of the C. funebris was evaluated using species distribution modelling. The outcomes of this current study revealed that the species was mainly distributed in mountainous forest areas, and climate variables played a major role in the distribution of this conifer tree. Under climate change, the threatened conifer will be mainly concentrated in mountainous forests and is projected to undergo contraction in distribution and shift northward. The conservation status of C. funebris is projected to be uplisted to “Near Threatened” status under the SSP5_8.5 scenario by 2040 and to the “Least Concern” status under all the other investigated climate and dispersal scenarios. Despite the high capacity of the species for adaptation to environmental changes, part of its AOO might be lost under severe climate change conditions. Key conservation areas were identified, and suggestions for redesigning some of the current natural reserves in the forested area where the species is found were proposed for the conservation of this key coniferous species. The stable area in the northwestern part of Yunnan in the Hengduan Mountain Forest can serve as a promising area for C. funebris reintroduction through afforestation programs.

Partitioning the components of soil respiration is crucial to understand and model carbon cycling in forest ecosystems. In this study, total soil respiration (R_S), autotrophic respiration (R_A), heterotrophic respiration (R_H), litter respiration (R_L), litterfall input and environmental factors were synchronously monitored for 2 years in a subtropical Michelia wilsonii forest of southwestern China. R_H rates were often higher than R_A rates during the two years except for the middle growing season (from July to September). The mean rate of Rs, R_A, R_H and R_L was 1.94 μmol m^-1 s^-1, 0.85 μmol m^-1 s^-1, 1.09 μmol m^-1 s^-1 and 0.65 μmol m^-1 s^-1, respectively, during the 2-year experiment. Annual CO₂ emission derived from R_A, R_H and R_L was 3.26 Mg C ha^-1 a^-1, 4.67 Mg C ha^-1 a^-1 and 2.61 Mg C ha^-1 a^-1, respectively, which accounted for 41.4%, 58.6% and 32.9% of R_S. Over the experimental period, the ratio of R_A/R_S increased with soil temperature but the opposite was true for R_H/R_S and R_L/R_S. The Q₁₀ value was 2.01, 4.01, 1.34 and 1.30, respectively, for R_S, R_A, R_H and R_L. Path analysis indicated that environmental variables and litterfall production together explained 82.0%, 86.8%, 42.9% and 34.7% variations of monthly fluxes of R_S, R_A, R_H and R_L, respectively. Taken together, our results highlight the differential responses of the components of R_S to environmental variables.

Carbon (C) and nutrients storages in soil organic layer play an important role in forest productivity in the alpine-gorge area. However, forest gaps during forest regeneration could regulate carbon and nutrients stocks in soil organic layer by controlling hydro-thermal environment conditions, but little information has been available on it. Therefore, concentrations and stocks of carbon, nitrogen (N) and phosphorus (P) in fresh litter layer (LL), fragmented litter layer (FL) and humified litter layer (HL) were investigated from gap center, canopy gap and expanded gap to closed canopy in an alpine forest of eastern Tibetan Plateau in later fall (October, 2013). The results showed that the forest gaps reduced the thicknesses of LL and FL, but increased the thickness of HL. Carbon concentrations in LL and FL decreased as affected by forest gaps, whereas both N and P concentrations increased regardless of soil organic layers. Moreover, forest gaps reduced C, N and P stocks in LL and FL, although which in HL increased. In addition, C, N and P stocks were significantly related to negative accumulated temperature regardless of soil organic layers. These results suggest that forest gap could promote carbon and nutrient releases from fresh litters, but limit carbon and nutrients output from humified litters in these alpine forests.

This work was aimed at establishing an effective approach for in vitro propagation of Ajuga lupulina Maxim, a medicinal and ornamental plant mainly found in eastern Xizang, in the western Sichuan region of China. We report an optimum response in the proliferation of axillary shoots from nodal segment explants (10.2 shoots/explant) on MS medium containing 3.0 mg L⁻¹ of 6-benzyladenine (BA). When BA and TDZ individually or in combination with NAA were employed for adventitious shoot regeneration, shoots and embryo-like structures (ELSs) were noted in the callus from leaf explants. The maximum response of 26.4 shoots /explant (81.6%) and 12.0 ELSs/explant were ascertained on MS medium with 4.0 mg L⁻¹ TDZ and 0.1 mg L⁻¹ NAA. The leaf despite browning still demonstrated a high regeneration capacity. TDZ (2.0 mg L⁻¹) and BA (2.0 mg L⁻¹) along with NAA (0.01 mg L⁻¹) were found to perform well for shoot regeneration via callus from shoot tip explants. The best for rooting was MS medium (half-strength) containing indole-3-butyric acid (IBA: 1.5 mg L⁻¹) and (NAA: 0.5 mg L⁻¹) with the maximum number of roots (25.8 per shoot) and the highest rooting frequency (81.71%). The survival of the plantlets in the greenhouse was 78.2% indicative of successful acclimatization. This work is the first report of a consistent, definitive, and unique protocol for A. lupulina regeneration, paving the way for the in vitro preservation of such significant genetic resources and also further allied systems based on such callus-based or embryo-based approaches.

Background: Citrus yellow vein-clearing virus (CYVCV) is a Mandarivirus that causes great economic losses in lemon production. CYVCV infection is associated with obvious yellow vein-clearing disease symptoms and is directly regulated by plant hormone responses. Methods: To understand how lemon plants respond to CYVCV infection, we performed transcriptomic and phytohormone metabolomics. Results: A total of 936 differentially expressed genes were identified, and 773 were downregulated. Salicylic acid and auxin levels increased after CYVCV infection, and phytohormone regulatory systems were also explored. Jasmonic acid and auxin levels decreased after the CYVCV challenge, and jasmonic acid and auxin signaling pathway components were mostly downregulated. The differentially expressed genes (DEGs) involved in the immune response to viral infection, including those related to cell wall integrity, lectin, microtubules, and mildew resistance locus O (MLO), may also provide new candidate targets for CYVCV control. Conclusions: Our findings provide new insights into the molecular changes underlying the pathogenesis of CYVCV in lemon plants.