Inhibition of ethylene action by 1-MCP in climacteric tree fruit including apple and pear has confirmed a number of ripening and senescence processes are regulated by ethylene.  For apple, respiration and acid loss, softening, volatile production, and chlorophyll metabolism are slowed in the absence of ethylene action resulting in delayed ripening and a greatly extended marketing period.  While similar responses are inducible with 1-MCP in pears, a lack of predictability as to when the capacity to ripen is regained currently limits wide scale commercialization.  Inhibition of ethylene action via postharvest 1-MCP exposure can also prevent development of a number of physiological disorders including superficial scald, soft scald, and senescent core flush, however, other disorders including peel and cortex CO₂ injury can be exacerbated following 1-MCP exposure.  The physiological mechanisms by which some of these disorders proceed are poorly understood and remain to be elucidated.  Recent availability of a 1-MCP formulation suitable for field use is allowing characterization of ethylene-dependent pre-harvest developmental processes.  Of particular interest is the role of ethylene in peel pigment metabolism including anthocyanin, xanthophyll, and carotenoid accumulation, chlorophyll degradation, fruit abscission, and pre-harvest firmness loss.  The horticultural utility of this formulation is also a subject of current research.