This experiment explores the regulatory mechanisms of various light qualities on the phenotypic plasticity of Quercus variabilis seedlings during their growth. The light conditions included blue light (BL), red light (RL), far-red light (FrL), a blend of RL and FrL with a ratio of 1:1 (RFr1:1L), and a blend of RL and FrL with a ratio of 1:2 (RFr1:2L), alongside a broad-spectrum white light (WL) as the control. Each treatment was maintained at a consistent photosynthetic photon flux density of 400 µmol·m⁻²·s⁻¹. Results indicate significant morphological variations in Q. variabilis seedlings under different light qualities. Compared to white light treatment, all light quality treatments enhance seedling height, with the FrL treatment exhibiting the most pronounced effect. Seedling ground diameter elongation is stimulated by all light quality treatments, except for the BL treatment. Although the BL treatment promotes leaf morphology in Q. variabilis seedlings, it inhibits root growth, leading to reduced biomass accumulation and a lower root-to-shoot ratio. FrL can mitigate the effects of RL. Under the FrL treatment, Q. variabilis seedlings exhibit a greater increase in plant height and a higher height-to-diameter ratio. While the leaf morphology of RFr1:1L treatment does not show significant advantages, it demonstrates substantial root growth, resulting in the highest biomass accumulation. Quercus variabilis displays the strongest morphological plasticity in its root system, showing greater sensitivity to variations in light quality compared to leaf morphology and biomass accumulation. Strategically optimizing light spectrum and wavelength can significantly boost economic yields and improve the quality of forestry products.

In forests, seedling renewal is influenced by many environmental factors, including climate change, seed size, wildfires, and ecological factors. It is unclear how different growth years of seedlings affect Chinese cork oak (Quercus variabilis) root endophyte communities. In this study, we took a holistic approach, using Illumina sequencing, to study the composition and function of bacterial communities associated with root microorganisms in four Q. variabilis seedlings after 1, 2, and 3 years of growth. The bacterial alpha diversity indexes were highest in the second year and lowest in the third year, and age was the decisive factor for the differences found in the root endophytic bacterial communities. Total phosphorus had the greatest effect on bacterial communities. The abundance of beneficial bacteria Streptomyces (8.69%) and Novosphingobium (4.22%) was highest in the second-year samples, and their abundance decreased by 7.96% and 3.61% in the third year, respectively. Higher levels of plant disease inhibition and metabolism (23.80%) were in the roots of second-year Q. variabilis seedlings. The metabolic abundance of carbohydrate was 3.66% lower in the first year and 3.95% lower in the third year compared to the second year. Our results suggest that the structure and function of bacterial communities changed with increasing growth years.

Substrate and rhizosphere microorganisms are key factors affecting seedling growth; however, the effects of seedling substrates and rhizosphere bacteria on the growth of Quercus variabilis are not completely understood. Here, Q. variabilis seedlings were grown in substrates with and without cork flour, as follows: H substrate (charcoal soil/cork flour/perlite, 1:1:2), S substrate (cork flour/perlite, 1:1), and the control (CK) substrate (charcoal soil/perlite, 3:2). High-throughput sequencing and qPCR were used to investigate the effects of these substrates on seedling growth, physiological indices, and rhizosphere bacterial communities. Root and shoot weights of seedlings grown in H and S substrates were significantly higher than those of seedlings grown in CK. Moreover, H was conducive to chlorophyll synthesis in seedling leaves, and the transpiration rate and intercellular CO₂ concentration of the leaves of seedlings grown in H were higher than those of seedlings grown in CK. The number of rhizosphere bacterial 16S rRNA copies was significantly greater in the case of seedlings grown in S than for those grown in H and CK. As well, rhizosphere bacterial richness was higher in seedlings grown in H and S than in those grown in CK. Thus, cork-flour-supplemented substrates are beneficial for seedling growth and development, seedling rhizosphere bacterial abundance and diversity, and the abundance of nitrogen and phosphorus metabolism-promoting microbial taxa.

Quercus suber L. (Q. suber) is an ecologically and industrially valuable species, yet faces challenges in propagation in China. This study optimized somatic embryogenesis (SE) protocols using two-year-old Q. suber leaves, focusing on petioles and leaf veins as the most responsive explants, with May as the optimal sampling time. The MSSH medium (a combination of Murashige and Skoog Medium (MS) major elements and Schenk and Hildebrandt Medium (SH) minor elements and vitamins) under darkness maximized transdifferentiation. Additionally, the highest callus induction was achieved with 0.50 mg/L 6-benzyladenine (6-BA) and 1.00 mg/L 1-Naphthaleneacetic acid (NAA). Liquid culture with 1.00 g inoculum and 0.50 mg/L 6-BA + 0.20 mg/L NAA achieved the best proliferation. Redifferentiation peaked at 0.15 mg/L NAA + 0.20 mg/L 6-BA. Transcriptome profiling identified 4534 differentially expressed genes (DEGs) between embryogenic callus (E1) and global embryos (E2), with key pathways linked to cell wall remodeling, stress responses, and photosynthesis. Key regulators identified during the early stage of callus redifferentiation include cytokinin oxidase 3 (CKX3), gibberellin-responsive protein (GH3.6), and pectin lyase 5 (PL5), among others. This study provides insights into efficient SE of Q. suber and the genes underlying early callus redifferentiation, laying the groundwork for future research.

There was an error in the last sentence in part “2.1. Study Area and Sample Collection”, and the first sentence in “2.3. DNA Extraction and PCR Amplification” in the original publication

Quercus variabilis is a key species for reforestation in East Asia, yet the mechanisms by which arbuscular mycorrhizal fungi (AMF) influence seedling growth and responses to soil-borne fungal challenge remain incompletely understood. This study combined physiological and metagenomic approaches to address this gap. Among seven rhizosphere fungal isolates, Fusarium tricinctum (F15) exerted the strongest growth-inhibitory effect on Q. variabilis seedlings and was therefore selected for subsequent experiments. Inoculation with the AMF Rhizophagus intraradices significantly promoted seedling growth (p < 0.05), increasing root length by 4.94% relative to the uninoculated control and increasing ground diameter and aboveground fresh weight by 28.57% and 117.07%, respectively, relative to F15-treated seedlings. AMF inoculation also significantly altered substrate nutrient status (p < 0.05), particularly nitrogen, phosphorus, and potassium, and enhanced the activity of antioxidant enzymes, including peroxidase and catalase (p < 0.05). Metagenomic analysis revealed that AMF significantly reshaped rhizosphere microbial community composition and bacterial α-diversity (p < 0.05), enriching beneficial taxa such as Mesorhizobium. Functional profiling showed differences in predicted microbial functional profiles between AMF-inoculated and F15-treated groups. Together, these results indicate that AMF enhances seedling growth and mitigates the negative effects associated with F15 challenge, potentially through altered substrate nutrient dynamics, enhanced antioxidant capacity, and modulation of the rhizosphere microbial community.