Do cytokinins, volatile isoprenoids and carotenoids synergically delay leaf senescence?

Ageing and senescence in plants are complex phenomena that often transcend human perception. Reactive oxygen species (ROS) are key factors influencing senescence, and photosynthetic electron transport within chloroplasts is a major source of ROS. Degradation of chloroplast genomes by ROS activity is a key aspect of leaf senescence. The chloroplast localized methylerythritol phosphate (MEP) pathway produces many de novo phytohormones, volatile isoprenoids and pigments that act as efficient antioxidants and photo-protectants in photosynthetic tissues. Volatile isoprenoids control ROS and help plants maintaining homeostasis under abiotic stresses. Cytokinins and carotenoids are key players in regulation of ageing and senescence in leaves. We analyse the MEP pathway as a set of two biochemical modules and discuss trade-offs and ontogenic trends in foliar levels of MEP end-products. We hypothesize that high in vivo cytokinin content, high volatile isoprenoid emission and high carotenoid content have synergistic functions in maintaining the integrity of photosystems and chloroplast genomes, and thus in preventing leaf senescence. This article is protected by copyright. All rights reserved.