Osmanthus fragrans is a well-known native plant in China, and carotenoids are the main group of pigments in the petals. Abscisic acid (ABA) is one of the products of the metabolic pathway of carotenoids. Application of ABA could affect pigmentation of flower petals by changing the carotenoid content. However, little is known about the effects of ABA treatment on carotenoid accumulation in O. fragrans. In this study, different concentrations of ABA (0, 150 and 200 mg/L) were spread on the petals of O. fragrans ‘Yanhonggui’. The petal color of ‘Yanhonggui’ receiving every ABA treatment was deeper than that of the control. The content of total carotenoids in the petals significantly increased with 200 mg/L ABA treatment. In the petals, α-carotene and β-carotene were the predominant carotenoids. The expression of several genes involved in the metabolism of carotenoids increased with 200 mg/L ABA treatment, including PSY1, PDS1, Z-ISO1, ZDS1, CRTISO, NCED3 and CCD4. However, the transcription levels of the latter two carotenoid degradation-related genes were much lower than of the five former carotenoid biosynthesis-related genes; the finding would explain the significant increase in total carotenoids in ‘Yanhonggui’ petals receiving the 200 mg/L ABA treatment.

The increase in the atmospheric carbon dioxide concentration promotes its accumulation in trees by regulating the synthesis and transportation genes for endogenous hormones, such as IAA and GA, which are key factors in regulating various life activities, including growth rings. To explore the impact of changes in endogenous hormone levels such as IAA and GA on the growth of tree rings, and to provide a basis for improving the management of hybrid larch clonal forests, we investigated the effects of exogenous indole-3-acetic acid (IAA), gibberellic acid 3 (GA₃), and their combination on tree-ring growth in hybrid larch. IAA, GA₃, and a combination treatment were sprayed on the leaves of one clone of a hybrid larch seedling every three days. Small blocks were collected at the base stems for sequential anatomical observations. The phytohormone type, instead of the concentration, had a more significant effect on wood formation. Specifically, IAA treatment at 300 mg L⁻¹ significantly increased latewood (LW) layers until 90 days after treatment (DAT). The 500 mg L⁻¹ treatment significantly increased the wall radial thickness (WRT) of latewood (LW) cells. GA₃ treatment at 100 mg L⁻¹ significantly decreased the layers and width of total wood (TW), LW, and earlywood (EW). The 300 mg L⁻¹ treatment significantly increased the WRT of EW. The IAA 100 mg L⁻¹ + GA₃ 100 mg L⁻¹ combination treatment significantly increased the layers and width of TW and LW by inducing cambium activity and increasing the rate of wood cell development. The WRT and lumen radial diameter (LRD) of EW or LW in this treatment were similar to those observed with the corresponding single phytohormone treatment. These results indicate that combination treatment at 100 mg L⁻¹ + 100 mg L⁻¹ was a better way to promote tree-ring growth. Our study suggests that changes in phytohormone levels and ratios are important factors that affect tree-ring formation. Hormone levels and ratios should be regarded as important indicators to guide the improvement of management practices in hybrid larch clonal plantations.

Red pigmentation in apple peel significantly contributes to its commercial value, and bagging treatment contributes to enhancing red coloration in fruits. However, the regulatory mechanisms underlying bagging-induced coloration remain largely unexplored. Through bagging treatment, this study aimed to investigate the role of DNA methylation in anthocyanin biosynthesis in the ‘Nagafu No. 2’ cultivar and its bud mutation variant, which has enhanced red coloration. We compared bagging and unbagging treatments in both the bud mutant (Mt-Bagging and Mt-NoBagging) and the wild type (Control-Bagging and Control-NoBagging). Our results demonstrated that bagging significantly promoted anthocyanin accumulation while reducing chlorophyll content. At 30 days post-bag removal, anthocyanin content was highest in the Mt-Bagging group, followed by the Mt-NoBagging, Control-Bagging, and Control-NoBagging groups, and the highest level of redness (a* values) was detected in the Mt-Bagging group. Genome-wide methylation analysis revealed that differentially methylated regions predominantly targeted structural genes within the anthocyanin biosynthesis pathway, including C4H1, C4H3, C4HL, ANS1, and ANS2. Notably, quantitative PCR analysis confirmed that the upregulation of C4HL, C4H3, and ANS1 in the bagged mutant correlated with its intensified red coloration. These findings offer novel insights into the epigenetic regulation of apple peel pigmentation during bagging cultivation.