*4.6. Plant Materials and Abiotic Stress Treatments*

The *Rhododendron* cultivar 'Yanzhi Mi' grown in the greenhouse at the Jiangsu Academy of Agricultural Sciences (Nanjing, China, 118.881 E, 32.039 N) was used in this study. In November 2022, four-year-old plants with closed buds that were grown in separate pots were grouped according to the treatments to be subjected to different abiotic stresses. For cold stress, the plants were placed in a paper box with a black plastic light-shielding bag. Two groups were placed in a 4 ◦C artificial cold storage room, while the control group was placed at room temperature. For salt and drought stress, the plants were placed in a greenhouse and treated with 200 mM NaCl or 260 mM mannitol, respectively, while the control group was treated with pure water. Closed buds were collected from every group at 4 and 24 h after treatment, frozen in liquid nitrogen immediately after sampling and then stored in a freezer at −80 ◦C.
