Editorial [ Hot Topic: Monoterpenoids in Plant-Plant Interactions (Guest Editor: Prof. Vincenzo De Feo)]

This issue “Monoterpenoids in plant-plant interactions” highlights the ecological role of these compounds in nature, peculiarly in natural and modified ecosystems, updating available literature. Terpenoids are a group of secondary metabolites with a variety of functions, playing important roles in plant-plant, plantinsect and plant-pathogens interactions. The production and accumulation of secondary metabolites, which inhibit and/or stimulate germination and development of other plants (allolochemicals), are important for understanding the mechanism of the ecological interactions. Among allelochemicals released by plants, volatile essential oils and monoterpenes have received much attention. Many studies have documented that volatile oils or their constituents inhibit and delay seed germination and inhibit the seedling growth of many weeds and cultivated crops. The phytotoxic effects of essential oil have increased the interest in exploring volatile oils from aromatic plants for potential weed management. The mechanisms by which monoterpenes released by certain species affect the germination and growth of other plants remain to be elucidated. The information available suggests that they interefere with some physiological processes, including respiration, mitosis, the action of phytohormones, antioxidant defence systems and membrane properties. Recently, in literature, the mechanism of action for α-pinene has been reported: such compound acts on mitochondria as an inhibitor of electron flow through cytochrome-oxidase pathway. This action likely leads to an increase in mitochondrial reactive oxygen species (ROS) production and consequently, to membrane lipoperoxidation. A perturabation on mitochondrial functions may thus be a primary mechanism of the phytotoxic action of some monoterpenes, particularly during seed germination and initial seedling growth when ATP production depends mainly on mitochondrial metabolism.