The study investigates the role of volatile organic compounds (VOCs) in plant communication and signaling, focusing on the perception and downstream effects of (−)-germacrene D, a sesquiterpene. Using Petunia hybrida as a model, researchers found that the karrikin-insensitive receptor PhKAI2ia stereospecifically perceives (−)-germacrene D, triggering a KAI2-mediated signaling cascade that affects plant fitness. The study highlights the involvement of the intermediate clade of KAI2 receptors and provides insights into plant olfaction and the nature of potential endogenous KAI2 ligands. Key findings include: 1. **VOC Perception and Signaling**: The perception of VOCs is compound-specific and affects plant fitness. PhKAI2ia, a unique intermediate clade receptor, is required for sesquiterpene perception and response in petunia stigmas. 2. **Stereo-Specific Perception**: PhKAI2ia stereo-specifically recognizes (−)-germacrene D, which is distinct from other enantiomers like (+)-germacrene D. 3. **Signaling Pathway**: The (−)-germacrene D-mediated signaling pathway relies on the KAI2ia-dependent pathway and shares some transcriptional gene targets with karrikin responses. 4. **Downstream Effects**: The KAI2ia-dependent signaling pathway operates via the PhMAX2 ubiquitin ligase to degrade the transcriptional co-repressor SMAX1a, leading to normal pistil development and seed yield. 5. **Genetic Evidence**: The study provides genetic evidence for the involvement of PhKAI2ia in VOC perception and signaling, showing that other *PhKAI2* genes cannot compensate for reduced PhKAI2ia activity. These findings contribute to our understanding of plant communication and highlight the importance of specific ligands and receptors in plant-VOC interactions.The study investigates the role of volatile organic compounds (VOCs) in plant communication and signaling, focusing on the perception and downstream effects of (−)-germacrene D, a sesquiterpene. Using Petunia hybrida as a model, researchers found that the karrikin-insensitive receptor PhKAI2ia stereospecifically perceives (−)-germacrene D, triggering a KAI2-mediated signaling cascade that affects plant fitness. The study highlights the involvement of the intermediate clade of KAI2 receptors and provides insights into plant olfaction and the nature of potential endogenous KAI2 ligands. Key findings include: 1. **VOC Perception and Signaling**: The perception of VOCs is compound-specific and affects plant fitness. PhKAI2ia, a unique intermediate clade receptor, is required for sesquiterpene perception and response in petunia stigmas. 2. **Stereo-Specific Perception**: PhKAI2ia stereo-specifically recognizes (−)-germacrene D, which is distinct from other enantiomers like (+)-germacrene D. 3. **Signaling Pathway**: The (−)-germacrene D-mediated signaling pathway relies on the KAI2ia-dependent pathway and shares some transcriptional gene targets with karrikin responses. 4. **Downstream Effects**: The KAI2ia-dependent signaling pathway operates via the PhMAX2 ubiquitin ligase to degrade the transcriptional co-repressor SMAX1a, leading to normal pistil development and seed yield. 5. **Genetic Evidence**: The study provides genetic evidence for the involvement of PhKAI2ia in VOC perception and signaling, showing that other *PhKAI2* genes cannot compensate for reduced PhKAI2ia activity. These findings contribute to our understanding of plant communication and highlight the importance of specific ligands and receptors in plant-VOC interactions.