Climacteric versus non-climacteric physiology

Fleshy fruits have been classified as climacteric or non-climacteric, depending on whether or not a fruit exhibits a peak in respiration and ethylene production during ripening. Ethylene, considered to be the ripening hormone, controls ripening by coordinating the timely activation of many genes. Considerable progress has been made in the characterization of the ethylene biosynthetic pathway. The emerging picture is one of ethylene-dependent and -independent pathways coexisting in both climacteric and nonclimacteric fruits. Besides ethylene, other hormones and environmental factors affect the ripening process, but their modes of action have been poorly studied. Further work is needed to understand the molecular events involved in the individual ripening processes.