Magnolia wufengensis is a new species of Magnolia L. and has considerable ornamental and economic value due to its unique characteristics. However, because of its characteristic of poor low temperature resistance, M. wufengensis is hardly popularization and application in the north of China. Furthermore, the mechanisms of gene regulation and signaling pathways involved in the cold-stress response remained unclear in this species. In order to solve the above-mentioned problems, we performed de novo transcriptome assembly and compared the gene expression under the natural (25 °C) and cold (4 °C) conditions for M. wufengensis seedlings. More than 46 million high-quality clean reads were produced from six samples (RNA was extracted from the leaves) and were used for performing de novo transcriptome assembly. A total of 59,764 non-redundant unigenes with an average length of 899 bp (N50 = 1,110) were generated. Among these unigenes, 31,038 unigenes exhibited significant sequence similarity to known genes, as determined by BLASTx searches (E-value ≤1.0E-05) against the Nr, SwissProt, String, GO, KEGG, and Cluster of COG databases. Based on a comparative transcriptome analysis, 3,910 unigenes were significantly differentially expressed (false discovery rate [FDR] < 0.05 and |log2FC (CT/CK)| ≥ 1) in the cold-treated samples, and 2,616 and 1,294 unigenes were up- and down-regulated by cold stress, respectively. Analysis of the expression patterns of 16 differentially expressed genes (DEGs) by quantitative real-time RT-PCR (qRT-PCR) confirmed the accuracy of the RNA-Seq results. Gene Ontology and KEGG pathway functional enrichment analyses allowed us to better understand these differentially expressed unigenes. The most significant transcriptomic changes observed under cold stress were related to plant hormone and signal transduction pathways, primary and secondary metabolism, and photosynthesis. In addition, 113 transcription factors, including members of the AP2-EREBP, bHLH, WRKY, MYB, NAC, HSF, and bZIP families, were identified as cold responsive. We generated a genome-wide transcript profile of M. wufengensis and a de novo-assembled transcriptome that can be used to analyze genes involved in biological processes. In this study, we provide the first report of transcriptome sequencing of cold-stressed M. wufengensis. Our findings provide important clues not only for understanding the molecular mechanisms of cold stress in plants but also for introducing cold hardiness into M. wufengensis.

Tree shape can affect microclimate, which may directly influence fruit growth and development. Open center and round head are two tree canopy shapes that are generally used in Camellia oleifera Abel. cultivation. To study the effects of the two canopy shapes on the microclimate and fruit quality parameters inside the canopy and investigate the correlations between microclimate and oil yield characteristics, microclimates in different developmental periods and fruit quality parameters at maturity at different positions in the two canopy shapes were determined. In this study, the open-center shape increased the light intensity and temperature, and reduced the relative humidity within the canopy, and the microclimate was more uniformly distributed within the open-center canopy. Fruit quality parameters of open-center canopied trees were also significantly increased and had more uniform distributions, especially the oil yield parameters. The content ratio of the dry seed, oil content ratio of the fresh fruit, and oil yield increased by 43.55%, 59.30% and 79.01%, in the lower layer, respectively, and 27.33%, 41.75%, and 55.43%, in the inner canopy, respectively, compared to those of round-head canopied trees. For both canopy shapes, oil yield parameters had positive correlations with light intensity and temperature, but negative correlations with relative humidity, and the correlation coefficients between light intensity and temperature at different developmental stages and oil yield parameters in round-head canopies were greater than in the open-center canopies. Additionally, regression equations between the single microclimatic factor in different developmental periods and oil yield parameters could be used to estimate the latter in the two canopy shapes. The optimum light conditions for open-center and round-head canopy shapes were 916–1893 and 1108–1259 μmol·m²·s⁻¹, respectively. Overall, the open-center canopy had a more desirable microclimate and a more uniform microclimate distribution, especially the light intensity, which contributes to high uniform fruit quality parameters. Thus, an open-center canopy is the desirable shape in C. oleifera production.

Magnolia wufengensis, a rare ornamental tree species, is now in a huge gap between market demand and actual supply of seedlings. As cutting propagation is one of the most important means to solve the shortage of seedling supply, this study developed an efficient cutting propagation procedure of M. wufengensis, revealed the morphological and histological changes of adventitious root formation, and explored the rhythm correlation between rooting process and physiological and biochemical changes. Cuttings pre-treated with NAA:IBA (2:1) exhibited the best rooting performance. Anatomical analysis demonstrated that adventitious root primordia of M. wufengensis were initiated from cambial and parenchyma cells of xylem, with no relationship to the callus formed on the epidermis. The rooting process of M. wufengenis can be divided into four periods: induction phase (0–8 dap) (dap means days after planting), initiation phase (8–13 dap), expression phase (13–18 dap), and extension phase (18–28 dap). NAA:IBA (2:1) induced the accumulations of 3-indoleacetic-acid and increased the contents of peroxidase and polyphenol-oxidase near the wounding at induction phase. The initiation phase, with the first histological modifications to the formation of meristemoids, correspond to the increase of peroxidase, polyphenol-oxidase, and soluble protein contents. The synergistic reaction of low 3-indoleacetic-acid and high levels of gibberellins and zeatin also stimulates the initiation phase. In the expression and extension phase, high activities of polyphenol-oxidase, IAA-oxidase, and increased contents of soluble protein co-stimulate the emergence and outgrowth of adventitious roots. The present study not only provides optimized protocol by application of auxin combination but also presents insights in the histological, morpho-physiological, and biochemical changes in stem cuttings of M. wufengensis.

Through this study, the most suitable fertilization ratio, amount and frequency were determined, providing a scientific reference for further fertilization management for Magnolia wufengensis (Magnoliaceae) seedlings. Fertilization is an important cultivation and management measure to maintain forest seedling health and rapid growth. However, improper fertilization can also have unexpected effects: inhibiting seedling growth, increasing the cost of production and contaminating the environment. Thus, to explore the most suitable fertilization treatment for Magnolia wufengensis growth, one-year-old Magnolia wufengensis seedlings and the orthogonal design method were used in this study. Three different fertilization frequencies were used combined with 9 NPK ratios. The growth index, chlorophyll content, nutrient content in tissues, nutrient transport efficiency, nutrient uptake, and soil properties were analyzed. Fertilization can increase chlorophyll content, promoting the vegetative growth and biomass accumulation of Magnolia wufengensis. Fertilization reduced the proportion of root biomass to whole plant biomass, resulting in an increase in stem biomass with little effect on leaf biomass. Additionally, fertilization also increased the proportion of N in roots, P in stems and K in leaves. Under fertilization, the K transport efficiency was higher than that of N and P. Furthermore, there was a positive correlation between the nutrient use efficiencies of N and K. Overall, the effects of six fertilizer applications were much better than those of four and eight fertilizer applications on the promotion of vegetative growth, biomass and nutrient accumulation, nutrient uptake and transport efficiency. The results showed that six fertilizer applications with an NPK ratio of 3:2:1 as follows: N application at 480 mg/plant, P application at 320 mg/plant, and K application at 160 mg/plant was the most suitable fertilization method for plant growth.