Apocarotenoid signals in plant development and beyond

Carotenoids are much more than the familiar yellow-to-red pigments that we find in fruits and flowers. Arguably it is the products of carotenoid breakdown-the apoca-rotenoids-that are most diverse in terms of chemical structure and biological function. The hydrocarbon back-bone presents a wide variety of positions for oxidative cleavage and chemical modification to produce com-pounds that serve as hormones, volatile aromas, and in-tracellular secondary messengers. In this Special Issue, we present a collection of articles that discuss the pro-duction, diversity, and function of apocarotenoids and re-lated compounds, particularly as plant growth regulators and as rhizospheric signalling molecules.