Identification of the Volatile Compounds and<i> </i>Observation of the Glandular Trichomes in <i>Opisthopappus taihangensis</i> and Four Species of <i>Chrysanthemum</i>

• Main Authors: Yanhong Guo, Tengxun Zhang, Jian Zhong, Tingting Ba, Ting Xu, Qixiang Zhang, Ming Sun
• Format: Article
• Language: English
• Published: MDPI AG 2020-07-01
• Series: Plants
• Subjects: volatile compounds; GC-MS; trichomes; density; histochemical; correlation
• Online Access: https://www.mdpi.com/2223-7747/9/7/855

<i>Opisthopappus taihangensis </i>(Ling) Shih, a wild relative germplasm of chrysanthemum, releases a completely different fragrance from chrysanthemum species. We aimed to identify the volatile compounds of the leaves of <i>O. taihangensis</i> and four other <i>Chrysanthemum</i> species using headspace solid-phase micro-extraction combined with gas chromatography-mass spectrometry (HS-SPME-GC/MS). In total, 70 compounds were detected, and terpenoids accounted for the largest percentage in these five species. Many specific compounds were only emitted from <i>O. taihangensis</i> and not from the other four species. In particular, 1,8-cineole could be responsible for the special leaf fragrance of <i>O. taihangensis</i> as it accounted for the largest proportion of the compounds in <i>O. taihangensis</i> but a small or no proportion at all in other species. The glandular trichomes (GTs) in the leaves are the main organs responsible for the emission of volatiles. To explore the relationship between the emissions and the density of the GTs on the leaf epidermis, the shape and density of the GTs were observed and calculated, respectively. The results showed that the trichomes have two shapes in these leaves: T-shaped non-glandular trichomes and capitate trichomes. Histochemical staining analyses indicated that terpenoids are mainly emitted from capitate glandular trichomes. Correlation analysis showed that the volatile amount of terpenoids is highly related to the density of capitate trichomes. In <i>O. taihangensis</i>, the terpenoids content and density of capitate trichomes are the highest. We identified the diversity of leaf volatiles from <i>O. taihangensis</i> and four other <i>Chrysanthemum</i> species and found a possible relationship between the content of volatile compounds and the density of capitate trichomes, which explained the cause of the fragrance of <i>O. taihangensis</i> leaves.