Comparative Analysis of Floral Volatile Organic Compounds in Five Endemic Impatiens Species from the Karst Region of Guizhou, China

To characterize floral volatile organic compounds (VOCs) in endemic Chinese Impatiens, we analyzed five karst-region species (I. blepharosepala, I. ganpiuana, I. bijieensis, I. liboensis, I. auriculata) using dynamic headspace adsorption and GC-MS, with PLS-DA and cluster analysis for interspecific comparison. A total of 293 VOCs belonging to nine compound classes were detected. Hydrocarbons (108 compounds) and esters (58 compounds) were predominant. VOC composition exhibited significant interspecific specificity, with I. ganpiuana (95) and I. auriculata (91) possessing the most diverse profiles, while I. liboensis (55) had the fewest. No VOCs were common to all five species. PLS-DA and cluster analysis grouped the five species into three distinct clusters. I. bijieensis exhibited the most unique VOC characteristics, whereas I. liboensis and I. auriculata showed high compositional similarity. Esters dominated in I. blepharosepala, I. ganpiuana, and I. bijieensis (39-45%), acids in I. liboensis (42%), and hydrocarbons in I. auriculata (19%). Nineteen key VOCs with VIP values > 1, including α-farnesene and 2,6-diphenylphenol, were identified as potential species-specific chemical markers. This study provides the first systematic characterization of floral VOCs in endemic Impatiens species from the karst region of Guizhou, China.