It is likely that from the time of the Roman Empire and perhaps before, peo
ple involved in the storage of plant material as food recognized that atmos
pheric modification can provide some benefit in improving storability. Howe
ver, active, commercial modification of the atmosphere for the preservation
of fresh fruit and vegetables dates to the early part of this century. Ear
ly successes with apple fruit has lead to the attempt to apply modified atm
ospheres to a wide range of commodities. Responses to atmospheric modificat
ion are found to vary dramatically among plant species, organ type and deve
lopmental stage and include both unwanted and beneficial physiological resp
onses, Desirable responses include a reduction in respiration, a reduction
in oxidative tissue damage or discoloration, a reduction in the rate of chl
orophyll degradation and a reduction in ethylene sensitivity with the conco
mitant reduction in the rate of ripening and other ethylene-mediated phenom
ena. Undesirable responses have included the induction of fermentation, the
development of disagreeable flavors? a reduction in aroma biosynthesis, th
e induction of tissue injury and an alteration in the makeup of microbial f
auna. The physiological bases for some of these responses to elevated CO2 a
nd reduced O-2 are discussed. (C) 1999 Elsevier Science B.V. All rights res
erved.