**3. Flower Scent**

Bohman et al. studied the mechanism of pollination in European *Ophrys* orchids, and they identified two new pollinator attractants, including (*Z*)-8-Heptadecene and *n*-pentadecane, and gained insights into the biosynthesis of semiochemicals [7]. Ramya et al. contributed a review to summarize the advances of volatile organic compounds in orchids mainly focusing on their gene expression patterns in different tissues and developmental stages of *Cymbidium* orchids as well as their key role in pollination ecology [8]. They proposed a molecular breeding strategy through the manipulation of floral traits to improve the quality of orchids in the future.

### **4. Plant-Microbial Interaction**

Orchids commonly have a symbiotic relationship with mycorrhizal fungi that benefit seed germination, seedling growth, and development. Sarsaiya et al. identified five species of myco-endophytes in *Dendrobium* orchids, and subsequent in vitro testing showed that they could affect seedling growth, especially at the stage of protocorms [9]. Zhang et al. profiled metabolome and transcriptome in the symbiosis between a mycorrhizal fungus, *Ceratobasidium* sp. AR2, and a medicinal orchid, *Anoectochilus roxburghii* [10]. They concluded that *C.* sp. AR2 could induce differential expressions, particularly in flavonoid biosynthetic genes and accomplished an increase in the accumulation of some flavonoids. They proposed that *C.* sp. AR2 has a high potential to enhance the quality of *A. roxburghii*.
