The significance of ethylene in the ripening of stored apples

Plants demonstrate various responses when subjected to relatively low concentrations of ethylene gas in the ambient air. The duration of exposure required depends on concentration and varies in different plants and according to stage and manner of growth. Several external factors may also influence the response of intact plants. Besides emissions from industrial installations, ethylene is produced externally from many natural sources and in consequence of human activities. The bulk of evidence suggests that ethylene is not at present a serious pollutant but we suggest that further and more precise research is required.