Volatile exchange between undamaged plants - a new mechanism affecting insect orientation in intercropping : Plant Communication Changes Host Plant Odour

Changes in plant volatile emission can be induced by exposure to volatiles from neighbouring insect-attacked plants.However, plants are also exposed to volatiles from unattacked neighbours, and the consequences of this have not beenexplored. We investigated whether volatile exchange between undamaged plants affects volatile emission and plant-insectinteraction. Consistently greater quantities of two terpenoids were found in the headspace of potato previously exposed tovolatiles from undamaged onion plants identified by mass spectrometry. Using live plants and synthetic blends mimickingexposed and unexposed potato, we tested the olfactory response of winged aphids, Myzus persicae. The altered potatovolatile profile deterred aphids in laboratory experiments. Further, we show that growing potato together with onion in thefield reduces the abundance of winged, host-seeking aphids. Our study broadens the ecological significance of thephenomenon; volatiles carry not only information on whether or not neighbouring plants are under attack, but alsoinformation on the emitter plants themselves. In this way responding plants could obtain information on whether theneighbouring plant is a competitive threat and can accordingly adjust their growth towards it. We interpret this as aresponse in the process of adaptation towards neighbouring plants. Furthermore, these physiological changes in theresponding plants have significant ecological impact, as behaviour of aphids was affected. Since herbivore host plants arepotentially under constant exposure to these volatiles, our study has major implications for the understanding of howmechanisms within plant communities affect insects. This knowledge could be used to improve plant protection andincrease scientific understanding of communication between plants and its impact on other organisms.