Foliar behaviour of biogenic semi-volatiles: potential applications in sustainable pest management

Abstract

Plants emit an extremely diverse bouquet of volatile organic compounds (VOCs) from their above-ground and below-ground parts. Emissions are constitutive or induced, e.g. by herbivores. VOCs can be classified as highly volatile, volatile and semivolatile compounds. Sesquiterpenes (SQTs) are typical semi-volatile organic compounds (sVOCs) released by plants. Similarly, herbivore-induced homoterpenes and methyl salicylate also have relatively low volatility. SVOCs have a high boiling point (> 240 °C) and a vapour pressure below 0.005 kPa at 25 °C. Glandular trichomes on plant surfaces can store SQTs in mixtures with more volatile VOCs, which are released into the air by diffusion or after gland rupture. The sVOCs stored in glandular trichomes often have repellent effects on herbivores, while herbivore-induced sVOCs are known for their attractiveness to natural enemies of herbivores, i.e. they act in indirect chemical defence of plants. Due to their low volatility, sVOCs produced by plants may easily adhere to the surfaces of emitter and neighbouring plants during the colder temperatures that plants face, e.g. at night. On the foliage of neighbouring receiver plants, sVOCs may act in direct and indirect defence of that plant species. When the temperature rises again, sVOCs are released into the atmosphere. The semi-volatile reaction products of highly volatile plant monoterpenes and photochemical pollutants such as ozone could constitute further sVOCs on plant leaf surfaces. Here, we review recent literature of the plant surface-environment interaction of biogenic sVOCs and particularly evaluate potential crop protection strategies such as intercropping and companion planting using sVOC-emitting species. Foliage typically forms the widest surfaces on crop plants, and foliar herbivory is a major type of pest damage during the vegetative stage of crop plants. Foliage is also a major source of herbivore-induced VOC emissions. Consequently, we focus on foliage-mediated sVOCs and their potential in pest management.

Unravelling the functions of biogenic volatiles in boreal and temperate forest ecosystems

“…Wilbon et al 2013). Terpenes with low carbon content such as isoprene (C 5 ) or MTs (C 10 ) are volatile or semi-volatile while compounds with a higher number of carbon atoms such as SQTs (C 15 ) are of semi-or low volatility (Mofikoya et al 2019).…”

The fate of methyl salicylate in the environment and its role as signal in multitrophic interactions

“…Here, MeSA can serve the dual role of a synergetic compound with insect pheromones, for example in facilitating the orientation to a sexual partner (Xu and Turlings, 2018), or antagonistically, by hampering this orientation (Rouyar et al, 2015), depending on the volatile, plant and insect species. The efficiency of transport within the atmosphere and the sensory mechanisms by which these compounds operate are so far unknown, but they have already been exploited in pest management programs, for example in combining a crop species with repelling or masking plants (Mofikoya et al, 2019). Like MeSA, other semiochemicals (especially pheromones) with similar physicochemical properties may partition to SOA, which could be instrumental in their atmospheric transport.…”

Functional Role of Extrafloral Nectar in Boreal Forest Ecosystems under Climate Change

“…Under warmer conditions, plant signaling to higher trophic levels with induced volatiles is improved [159], partly due to increased volatility of volatile and semivolatile compounds [160]. This results in an increased capacity of plant species to attract predators and reduce the effects of herbivores on plant communities [154].…”