Plants have evolved several mechanisms for getting rid of excess energy in photosynthetic membranes, some of which involve isoprenoid compounds. In all photosynthetic organisms, the carotenoids β-carotene and zeaxanthin, and tocopherols serve an important photoprotective role, either by dissipating excess excitation energy as heat or by scavenging reactive oxygen species (ROS) and suppressing lipid peroxidation. Isoprene and some monoterpenes, diterpenes and other carotenoids also occur in some plant lineages. Compelling evidence indicates that these non-ubiquitous isoprenoids might be particularly relevant in adapting plants to adverse climatic conditions by serving as additional and/or alternative protection mechanisms. © 2005 Elsevier Ltd. All rights reserved.