Volatile isoprenoids and their importance for protection against environmental constraints in the Mediterranean area

Among plant secondary metabolites, volatile isoprenoids have received increasing attention because they are involved in a range of physiological and ecological interactions, often helping plants cope with abiotic and biotic stressors, and potentially affecting the chemistry of the troposphere once they are emitted in the air. We review evidence about the beneficial functions of volatile isoprenoids in leaves, principally as antioxidants and membrane stabilizing agents, avoiding heat damage. Because the Mediterranean environment is characterized by prolonged dry and hot seasons, and recurrent heat-waves, we surmise that volatile isoprenoids are particularly widespread, and play an important physiological role, in Mediterranean woody plants. Based on a review of available inventories, isoprene emission characterizes deciduous woody plants, whereas evergreens are more often monoterpene emitters. Monoterpene emitters may be better fit to the Mediterranean climate, and, in general, to climate conditions favoring evergreens.