Volatile organic compounds are important mediators of mutualistic interactions between plants and their physical and biological surroundings. Volatiles rapidly indicate competition or potential threat before these can take place, and they regulate and coordinate adaptation responses in neighbouring plants, fine-tuning them to match the exact stress encountered. Ecological specificity and context-dependency of plant-plant communication mediated by volatiles represent important factors that determine plant performance in specific environments. In this review, we synthesise the recent progress made in understanding the role of plant volatiles as mediators of plant interactions at the individual and community levels, highlighting the complexity of the plant receiver response to diverse volatile cues and signals and addressing how specific responses shape plant growth and survival. Finally, we outline the knowledge gaps and provide directions for future research. The complex dialogue between the emitter and receiver based on either volatile cues or signals determines the outcome of information exchange, which shapes the communication pattern between individuals at the community level and determines their ecological implications at other trophic levels.

One of the most important challenges for individual plants is coexistence with their neighbors. To compensate for their sessile lifestyle, plants developed complex and sophisticated chemical systems of communication among each other. Site-specific biotic and abiotic factors constantly alter the physiological activity of plants, which causes them to release various secondary metabolites in their environments. Volatile organic compounds (VOCs) are the most common cues that reflect a plant's current physiological status. In this sense, the identity of its immediate neighbors may have the greatest impact for a plant, as they share the same available resources. Plants constantly monitor and respond to these cues with great sensitivity and discrimination, resulting in specific changes in their growth pattern and adjusting their physiology, morphology, and phenotype accordingly. Those typical competition responses in receivers may increase their fitness as they can be elicited even before the competition takes place. Plant-plant interactions are dynamic and complex as they can include many different and important surrounding cues. A major challenge for all individual plants is detecting and actively responding only to "true" cues that point to real upcoming threat. Such selective responses to highly specific cues embedded in volatile bouquets are of great ecological importance in understanding plant-plant interactions. We have reviewed recent research on the role of VOCs in complex plant-plant interactions in plant-cross kingdom and highlighted their influence on organisms at higher trophic levels.

The present study tested in the Western Dutch Wadden Sea (WDW) UNESCO World Heritage Site why an on a global scale the aggressive non-indigenous red drift alga Gracilaria vermiculophylla didn't succeed to overgrow the WDC. In such a multifaceted complex ecosystem like the dynamic WDC it seems like unraveling a Gordian knob in order to describe the inextricable relationship between this seaweed invader suppression and its (a) biotic environment. However, we succeeded at the molecular level to give a convincing reasoning at first grounded in the awareness of a since 1987 river Rhine-North-Sea-WDC severely Phosphorus (P) restricted ecosystem. Our ecological datasets gave via final DCA (Detrended Correspondence Analysis) awareness of the very compelling interaction between Ulva sp. and G.vermiculophylla. Based on LCMS-techniques we discovered that Ulva sp. have the advantage to use the biochemical pathway solely rarely observed in some euckaryotes-to have the potential to produce the betaine lipid diacylglyceryl-O-4'-(N,N,N,-trimethyl)homoserine (DGTS) which replaces the plant/seaweed cell wall structure phosphatidylcholine (PC) "lecithine" under phosphate-limiting growth conditions. Also we hope this lipidomics based compound DGTS can serve as an ecological biomarker in order to protect vulnerable ecosystems like the Wadden Sea (UNESCO World Heritage).

International shipping comprises an environmental risk: import of ecosystem foreign, and potentially harmful and disease-causing organisms, called non-indigenous species (NIS). One of the main vectors of introduction of NIS in ports is discharged ballast water of ships.